Phosphorus (P) loss by various pathways in constructed wetlands (CWs) is often variable. The effects of intermittent aeration and different construction waste substrates (gravel, red brick, fly-ash brick) on P processing using six batch-operated vertical flow constructed wetlands (VFCWs) were studied for decentralized domestic wastewater treatment. Average removal of total phosphorus (TP) in three aerated CWs was markedly higher (21.06, 24.83, and 27.02 mg m−2 day−1, respectively) than non-aerated CWs (10.64, 18.16, and 25.09 mg m−2 day−1, respectively). Fly-ash brick offered superior TP removal efficiency in both aerated and non-aerated batch-operated VFCWs, suggesting its promising application for P removal in CWs. Aeration greatly promoted plant growth and thusly increased plant uptake of P by 0.57–1.45 times. Substance storage was still the main P sink accounting for 23.92–59.47% of TP removal. Other process including microbial uptake was revealed to be a very important P removal pathway (accounting for 14.86–34.84%). The contribution of microbial uptake was also indicated by microbial analysis. Long-term results suggested that the contribution of microbial P uptake could be always ignored and underestimated in most CWs. A combination of intermittent aeration and suitable substrates is effective to intensify P transformation in CWs.

•FWS CWs were used to treat sewage treatment plant effluent for about two years.•Annual and seasonal variations of CH4 and N2O fluxes from FWS CWs were observed.•FWS CWs might be the significant source of CH4 and N2O.•Temperatures and plant species had an impact on CH4 and N2O emission.Constructed wetlands (CWs) have been used as a green technology to treat various wastewaters for several decades, and greenhouse gases production in these systems attracted increasing attention considering the contributions of methane and nitrous oxide emissions to global warming. However, the detailed knowledge about the contribution of CWs to methane and nitrous oxide emissions in treating sewage treatment plant effluent are still limited in particular for a better understanding of the sustainability of CWs. The fluxes of methane (CH4) and nitrous oxide (N2O) from free water surface (FWS) CWs in northern China were measured continuously using the static-stationary chamber technique from 2012 to 2013. The results showed that CWs were the significant source of CH4 and N2O emissions. Average emission rates of CH4 and N2O ranged from −30.2 μg m−2 h−1 to 450.9 μg m−2 h−1, and -58.8 μg m−2 h−1 to 1251.8 μg m−2 h−1, respectively. Obvious annual and seasonal variations of CH4 and N2O emissions were observed over the 2-year period. In addition, temperatures and plant species had an impact on CH4 and N2O emissions. The obtained results showed that FWS CWs, improving water quality but emitting lower CH4 and N2O, could be the alternative method for sewage treatment plant effluent.Download high-res image (277KB)Download full-size image

•A novel ammoniation-activation method (AAM) to prepare activated carbon was developed.•The AAM dramatically enhanced the BET surface area, porosity and functional groups of produced carbon.•The activated carbon prepared by AAM exhibited higher adsorption capacity than that of prepared by conventional method.Here, we describe an innovative ammoniation-activation method (AAM) to prepare activated carbon with enhanced porosity and functionality (acidity and basicity). Three ammoniating agents (i.e. NH3H2O, urea, and NH4HCO3) were employed to ammoniate the lignocellulosic precursors while H3PO4 was used as the activating agent. X-ray diffraction (XRD), scanning electron microscope (SEM), elemental analysis, and thermogravimetric analysis to characterize the ammoniation of precursors, and the produced carbons were characterized by N2 adsorption/desorption isotherms, elemental analysis, Boehm's titration method, and X-ray photoelectron spectroscopy (XPS). The results show that the BET surface area, pore volume and amount of functional groups of the carbon from the AAM method (hereafter termed AAC) were higher than those obtained conventional methods (AC). Accordingly, the AAC demonstrated > 20% higher adsorptive capacity for iodine than that of AC.Download high-res image (146KB)Download full-size image

Ammonia-oxidizing archaea (AOA) have aroused great attention since it can supplement nitrogen cycle and show extensive existence relative to its bacterial counterpart, ammonia-oxidizing bacteria (AOB). This study compared the abundance and community compositions of AOA and AOB between natural and constructed wetlands under low temperature. More complex community structures were obtained in the constructed wetland, which may be ascribed to the differences in available nutrient contents. Nitrosospira-like organisms predominated AOB communities in both wetlands. Nitrososphaera cluster dominated the AOA community in the constructed wetland, while both Nitrososphaera and Nitrosopumilus clusters were dominant in the natural wetland. AOA dominated over AOB in both the natural and constructed wetlands, and AOA to AOB ratio ranged from 1.47 to 8.13. The natural wetland showed higher nitrification potential at low temperature, mainly due to its higher AOA to AOB ratio. This also explained why a better ammonia treatment performance was observed in the natural wetland even when it had high influent concentrations. The present results provided some new insights to ammonia removal in the wetlands under low temperature.

•Ammoniation-activation method (AAM) to prepare activated carbon is created.•The preparation parameters of AAM are optimized by orthogonal experiments.•The pore volume parameters and the surface chemical characterizations of the prepared activated carbons are measured.•The influences of environmental factors on the Ni(II) sorption by formulated activated carbon are investigated.•The mechanisms of Ni(II) sorption on the carbon are investigated by XPS.Activated carbon (AC) is an adsorbent that is used extensively in environmental treatment, and improving its performance and reducing costs remain sustainable goals. To reduce production costs and attain a green production process, a novel ammoniation-activation method (AAM) for the preparation of AC to enhance its physicochemical and adsorptive performance was provided. The experimental parameters were optimized by orthogonal experiments and the carbon product was characterized. These results show that the SBET (1142.0 m2/g), Vtot (0.618 cm3/g) and content of carbon functional groups (2.953 mmol/g) from the AAM method (hereafter termed AAC) were higher than those obtained by conventional methods (AC, 863.6 m2/g, 0.506 cm3/g and 2.071 mmol/g, respectively). Accordingly, the AAC (38.91 mg/g) demonstrated a 30% higher adsorptive capacity for Ni(II) than the AC (27.55 mg/g). Furthermore, the behavior of Ni(II) sorption on the AAC was investigated by batch experiments using various Ni(II) concentrations, time durations, pH levels and ionic strengths. The associated sorption isotherms and kinetics well fitted to the Langmuir model and pseudo-second-order model, respectively. Possible sorption mechanisms were further explored by XPS. The chemical affinity of Ni(II) toward oxygen- and nitrogen-containing groups plays a key role in the sorption process.Download high-res image (197KB)Download full-size image

•The integrated T. orientalis-T. tubifex-substrate-microbes SFCWs is investigated.•The T. tubifex added SFCWs significantly enhance TN and TP removal from wastewater.•Bioturbation with T. tubifex provides sufficient carbon source for denitrification.•Increased particulate and colloidal P by T. tubifex promoting P removal in SFCWs.This study designed a combined benthic fauna-T. orientalis-substrate-microbes surface-flow constructed wetlands (SFCWs) through the addition of T. tubifex. Results showed that, the removal efficiencies of nitrogen and phosphorus in the tested SFCWs achieved 81.14 ± 4.16% and 70.49 ± 7.60%, which were 22.27% and 27.35% higher than that without T. tubifex. Lower nitrate (2.11 ± 0.79 mg/L) and ammonium (0.75 ± 0.64 mg/L) were also observed in the tested SFCWs, which were 3.46 mg/L and 0.52 mg/L lower than that without T. tubifex. Microbial study confirmed the increased denitrifiers with T. tubifex. The lower nitrogen in effluent was also attributed to higher contents of nitrogen storage in sediment and T. orientalis due to the bioturbation of T. tubifex. Furthermore, with T. tubifex, higher proportions of particulate (22.66 ± 3.96%) and colloidal phosphorus (20.57 ± 3.39%) observed promoted phosphorus settlement and further absorption by T. orientalis. The outcomes of this study provides an ecological and economical strategy for improving the performance of SFCWs.Download high-res image (129KB)Download full-size image

•Humic acid (HA) was used as a modifying agent for activated carbon preparation.•Oxygen-containing functional groups on the surfaces of the prepared activated carbon was enhanced.•The prepared activated carbon was exhibited rapid and efficient performance of Pb(II) removal from aqueous solutions.•The adsorption mechanisms of Pb(II) were investigated by XPS study.This study developed an humic acid (HA) in-situ modified activated carbon adsorbent (AC-HA) for the rapid and efficient removal of Pb(II) from aqueous media, and adsorption mechanisms are discussed. The physicochemical characteristics of activated carbons (AC) were investigated via N2 adsorption/desorption, scanning electron microscopy (SEM), Boehm's titration method and Fourier transform infrared spectroscopy (FTIR). AC-HA exhibited richer oxygen-containing functional groups than the original AC. In addition, the removal performance of AC-HA (250.0 mg/g) toward Pb(II) was greatly improved compared with the original AC (166.7 mg/g). The batch adsorption study results revealed that the Pb(II) adsorption data were best fit by the pseudo-second-order model of kinetics and Langmuir isotherm of isothermals, and therefore, the effect of the solution pH was studied. The superior performance of AC-HA was attributed to the HA modification, which contains numbers of groups and has a strong π-π interaction binding energy with AC and Pb(II) species. The adsorption mechanisms were confirmed via the XPS study. More importantly, the modified method is simple and has a low cost of production.Download high-res image (383KB)Download full-size image

•DAP was used as a novel, effective, low cost activating agent in activated carbon preparation.•The physical and chemical properties of activated carbons were characterized.•The processes of activation were investigated in this paper.•The Cr(VI) adsorption behaviors and mechanisms onto the activated carbon were studied.This work presents a one-step method for preparing a nitrogen-functionalized carbon adsorbent derived from biomass by diammonium hydrogen phosphate (DAP) activation for Cr(VI) removal. The activation mechanisms and nitrogen functionality were measured by thermogravimetric analysis. The effects of the preparation parameters on the properties of the final carbon adsorbent were examined by N2 adsorption/desorption and Boehm's titration. The optimum parameters of preparation are a heating temperature of 700 °C and impregnation ratio of 1.5. The produced carbon adsorbent shows an excellent micropore structure and a wealth of nitrogen-containing functional groups. The carbon adsorbent was used for Cr(VI) removal and showed a high adsorption capacity (43.86 mg/g). The adsorption kinetics, isotherms, pH effects and adsorption mechanisms were investigated. The results show that the adsorption data are well fitted by a pseudo-second-order model and the Freundlich model. The adsorption capacity of the activated carbon decreased with increasing solution pH. Microporous entrapment, NH3+ adsorption and OH reduction all played key roles in the Cr(VI) removal process.Download high-res image (209KB)Download full-size image

•Hydraulic flow pattern of constructed wetland was successfully detected by using isotopic technology.•Hydraulic flow pattern has significant influence on NH4+-N distribution characteristic.•Two wetland design suggestions were proposed in the study.The treatment efficiency of constructed wetlands (CWs) is highly dependent on the stability of the hydraulic flow patterns. To date, general technologies used to study hydraulic flow patterns of CWs mainly include tracer method, model simulation and velocity measurement, which are either expensive, empirical, or having secondary pollution. In this study, a new technology, which was based on the isotopic composition variation in CWs, was applied to detect the hydraulic flow patterns of two different CWs. Results showed that the hydraulic flow patterns of the two studied wetlands could be detected effectively by using hydrogen and oxygen isotopes. Furthermore, the locations of stagnant areas (SAs) and preferential flow areas (PFAs) were also determined. Significant regional difference in isotopic composition existed inside each CW, and two wetland design suggestions are proposed after hydraulic analysis. One is that the influent of CWs is supposed to be distributed uniformly, and another piece of advice is that the vegetation in the direction perpendicular to water flow should be maintained at the same types and density.

In rivers, nitrate/nitrite concentrations often vary with seasons and locations, and excess nitrogen can cause eutrophication. Constructed wetlands (CWs) have been used as a typical and optimal ecological technology to purify river water. In the present study, nitrogen (N) removal and related microbial mechanisms of treating high nitrate/nitrite polluted river water were explored in CW microcosms. Excellent removal performances were simultaneously achieved with low and stable effluent concentrations of NO3−–N (0.29–0.51 mg L−1), NO2−–N (0.65–1.0 mg L−1), NH4+–N (0.18–0.40 mg L−1), and TN (1.24–1.56 mg L−1) in our experimental and control groups. Based on the mass balance approach, plant uptake eliminated 11–14% of the total N input and sediment storage contributed 5–11% of N removal, indicating assimilation into biomass and sediment might be important sections of N removal besides microbial nitrification and denitrification. According to the 16S rRNA gene sequencing results, nitrate had positive effects on microbial community richness and diversity. Proteobacteria were particularly identified to be the dominant bacterial strains involved in N transformation in CWs and accounted for 37.26–52.99%. The relative abundance of Proteobacteria was highest after adding nitrate. Gamma- and beta-Proteobacteria were probably responsible for nitrate biodegradation. Bacillus and Cyanobacteria were speculated to be responsible for N removal and transformation. Overall, the results in this study could provide suggestions for treating high nitrate/nitrite polluted river water.

This study shows that oxalic acid (OA) and succinic acid (SA) were employed to modify Phragmites australis (PA)-based activated carbons (ACs) during phosphoric acid activation to improve Rhodamine B (RhB) removal from aqueous solutions. This study shows that oxalic acid (OA) and succinic acid (SA) were employed to modify Phragmites australis (PA)-based activated carbons (ACs) during phosphoric acid activation to improve Rhodamine B (RhB) removal from aqueous solutions. The unmodified activated carbon (AC), OA-modified and SA-modified ACs (AC-OA and AC-SA) were characterized by N2 adsorption/desorption, Boehm's titration, pHpzc and FT-IR analysis. It was found that the BET surface area of AC-OA (1040.36 m2 g−1) and AC-SA (1775.01 m2 g−1) was larger than unmodified AC (745.68 m2 g−1). In addition, AC-OA (2.987 mmol g−1) and AC-SA (3.194 mmol g−1) exhibited dramatically higher surface acidity than AC (1.852 mmol g−1). The RhB adsorption capacities of ACs were further investigated at different contact times, pHs, and ionic strengths. The adsorption equilibrium data of ACs were properly fitted to the Langmuir model. The kinetic studies show that the adsorption of RhB proceeds according to the pseudo-second order kinetics. The maximum RhB adsorption capacities of AC-OA (550.9 mg g−1) and AC-SA (629.8 mg g−1) were significantly higher than that of AC (417.1 mg g−1) due to their larger BET surface areas. Higher RhB adsorption could be attributed to their surface acidic functional groups.

Phragmites australis carbon (PAC) was produced from Phragmites australis by phosphoric acid (H3PO4) activation. To achieve a better amoxicillin (AMX) adsorption performance, manganous dihydrogen phosphate (Mn(H2PO4)2) and manganese chloride (MnCl2) were impregnated, producing PAC-MP and PAC-MC, respectively. Adsorption studies were carried out in different initial AMX concentration (15–100 mg L−1), pH (2–10) and contact time (0–60 h) to evaluate AMX adsorption performance and mechanisms. The adsorption isotherms well agreed with the Langmuir model for the three adsorbents. The maximum AMX adsorption capacity on PAC, PAC-MP and PAC-MC was 110, 132 and 122 mg g−1, respectively. Solution pH had a strong influence on AMX adsorption. For kinetic results, a significant desorption phenomenon was observed. Several possible mechanisms were elaborated which include electrostatic interaction, complexation and degradation of AMX molecules. On the whole, Mn-impregnated PAC showed superior AMX removal efficiency, which presents a promising modification method for activated carbon in the treatment of AMX containing wastewater.

In this research, the role of plants in improving microorganism growth conditions in subsurface flow constructed wetland (CW) microcosms was determined. In particular, microbial abundance and community were investigated during summer and winter in Phragmites australis-planted CW microcosms (PA) and unplanted CW microcosms (control, CT). Results revealed that the removal efficiencies of pollutants and microbial community structure varied in winter with variable microbial abundance. During summer, PA comprised more dominant phyla (e.g., Proteobacteria, Actinobacteria, and Bacteroidetes), whereas CT contained more Cyanobacteria and photosynthetic bacteria. During winter, the abundance of Proteobacteria was >40 % in PA but dramatically decreased in CT. Moreover, Cyanobacteria and photosynthetic bacterial dominance in CT decreased. In both seasons, bacteria were more abundant in root surfaces than in sand. Plant presence positively affected microbial abundance and community. The potential removal ability of CT, in which Cyanobacteria and photosynthetic bacteria were abundant during summer, was more significantly affected by temperature reduction than that of PA with plant presence.

Five different types of activated carbon varying in porosity, structure, and functional groups were prepared and used as adsorbents. The effect of the key properties of each activated carbon on its adsorption capacity, rate and mechanisms on trimethoprim (TMP) removal were evaluated. The kinetics results suggested that chemical adsorption interactions and particle diffusion into micropores were the main rate-control steps for TMP adsorption, and the existence of mesopores promoted the diffusion of TMP into internal pores. The adsorption of TMP onto activated carbon can be attributed to the pore-filling effect (micropores and some narrow mesopores) and strong adsorptive interactions with the graphene surface or oxygenated groups. Regarding the surface area-normalized adsorption of TMP, porous activated carbon exhibited 50–500 times lower adsorption than nonporous carbon adsorbent due to the size-exclusion effect, especially when oxygen complexes presented on the edges of the pores of the activated carbon. From a system design point of view, a fast adsorption rate and high adsorption capacity are normally required, and these findings imply that activated carbon with high microporosity, a certain mesoporosity and approachable surface groups can have great application potential for TMP removal.

The feasibility of preparing activated carbon (AC-CHs) from carbohydrates (glucose, sucrose and starch) with phosphoric acid activation was evaluated by comparing its physicochemical properties and Ni(II) adsorption performance with a reference activated carbon (AC-PA) derived from Phragmites australis. The textural and chemical properties of the prepared activated carbon were characterized by N2 adsorption/desorption isotherms, SEM, Boehm's titration and XPS. Although AC-CHs had much lower surface area (less than 700 m2 g−1) than AC-PA (1057 m2 g−1), they exhibited 45–70% larger Ni(II) adsorption capacity which could be mainly attributed to their 50–75% higher contents of total acidic and basic groups. The comparison of XPS analyses for starch-based activated carbon before and after Ni(II) adsorption indicated that Ni(II) cation combined with the oxygen-containing groups and basic groups (delocalized π-electrons) through the mechanisms of proton exchange, electrostatic attraction, and surface complexation. Kinetic results suggested that chemical reaction was the main rate-controlling step, and a very quick Ni(II) adsorption performance of AC-CHs was presented with ∼95% of maximum adsorption within 30 min. Both adsorption capacity and rate of the activated carbon depended on the surface chemistry as revealed by batch adsorption experiments and XPS analyses. This study demonstrated that AC-CHs could be promising materials for Ni(II) pollution minimization.

The present paper evaluated the feasibility of synthetizing activated carbons from xylitol with phosphoric acid activation at mild temperatures. Activation temperature (250–450 °C) and phosphoric acid to xylitol impregnation ratio (0.2–3 wt%) were varied during the synthesis of xylitol-based activated carbon, and the effects of these parameters on the textural and chemical properties of the final activated carbons were investigated by XRD, Raman, N2 adsorption and desorption, SEM, XPS and Boehm's titration. The results of yield, XRD and Raman indicated that phosphoric acid activation enhanced the yields of activated carbons, and facilitated the formation of completely carbonized materials at low temperatures (around 250 °C) by comparing with charcoals derived from pyrolysis of xylitol. The porous structures of the activated carbons were developed after activation, and for each activation temperature, the carbons reached the maximum surface area at an impregnation ratio of 1.5. Due to the strong oxidizing radicals decomposed from phosphates, the produced carbons contain relatively high concentrations of acidic and basic surface groups. The total surface groups peaked at 6.08 mmol g−1 for activated carbon obtained at an activation temperature of 350 °C and impregnation ratio of 1.5. The Ni(II) adsorption capacity of the activated carbons was 4 to 7 folds that of the charcoals.

Metal accumulation in fish is a global public health concern, because the consumption of contaminated fish accounts for the primary exposure of humans to toxic metals. In this study, the concentrations of arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg) in Crucian carp (Carassius auratus),Yellow catfish (Pelteobagrus fulvidraco), and Bighead carp (Hypophthalmichthys nobilis) from Nansi Lake of China were evaluated, and compared with the corresponding historical values in 2001 when the government started to govern water environment effectively. Bioaccumulation of heavy metal was highest in P.fulvidraco, followed by C.auratus and H.nobilis. The concentrations of Pb, As, Cd were much lower than the historical values, but Hg concentration was higher, suggesting that heavy metal pollution problem in fish from Nansi Lake still exists. Health hazard assessment showed no health risk from exposure to Pb, As, Cd, and Hg by consuming fish from this lake.

•Mushroom roots (MR) were used as raw materials to prepare activated carbons.•H3PO4, H4P2O7, H6P4O13 and C6H18O24P6 were employed as activating agents.•H4P2O7, H6P4O13 and C6H18O24P6 activation generated more surface acidic groups.•MRAC-C6H16O24P6 had the largest surface area and micropore volume.Orthophosphoric acid (H3PO4), pyrophosphoric acid (H4P2O7), polyphosphoric acid (H6P4O13) and phytic acid (C6H18O24P6) were specially employed as activating agents to produce activated carbons from mushroom roots (MR). Thermogravimetric studies of MR after these phosphorus oxyacids (POA) impregnation indicated the thermal degradation of MR was greatly influenced by different polycondensed POA. The prepared activated carbons were characterized by N2 adsorption/desorption isotherms, Fourier-transform infrared spectroscopy (FTIR) and Boehm's titration. The surface area of the carbons was similar but the characteristics of pore volume were different. MRAC-C6H16O24P6 owned the largest surface area and micropore volume. MRAC-H3PO4, MRAC-H4P2O7 and MRAC-H6P4O13 presented a similar micropore volume. MRAC-H6P4O13 exhibited a comparatively narrow mesopore distribution around 4 nm. Boehm's titration results indicated that MRAC-C6H16O24P6, MRAC-H6P4O13 and MRAC-H4P2O7 had much more acidic functionalities than MRAC-H3PO4. MRAC-C6H18O24P6 had the highest amount of total acidic surface groups (4.02 mmol/g). Batched sorption studies were also performed to compare adsorptive properties of the carbons toward methylene blue (MB). The sorption capacity of MB follows an order of MRAC-C6H16O24P6 ≈ MRAC-H6P4O13 > MRAC-H4P2O7 > MRAC-H3PO4, which may be assigned to the different pore structures and chemical properties.

This study attempts to elucidate the effect of sludge properties on the formation time, filtration resistance, and fouling propensity of self-forming dynamic membranes (SFDMs), developed on coarse-pore filters in aerobic wastewater treatment bioreactors. Short-term filtration experiments were performed with twenty aerobic sludge samples having twelve sludge properties characterized. Statistical analysis showed that mean particle diameter (Dvm) associated with particle size distribution strongly affected both formation time (rp=−0.803, p=0.000) and filtration resistance (rp=−0.733, p=0.000) of SFDMs, whereas relative hydrophobicity (RH) exhibited a moderate correlation with SFDM formation time (rp=−0.487, p=0.029). In contrast, four other different sludge properties, i.e. viscosity (rp=0.811, p=0.000), extractable extracellular polymeric substances (eEPS) (rp=0.723, p=0.000), the carbohydrate content of eEPS (rp=0.766, p=0.000), and specific oxygen uptake rate (SOUR) (rp=−0.610, p=0.004), were identified as having significant impact on the fouling propensity of fresh SFDMs. Besides statistical analysis, more detailed experimental evidences were obtained by directly examining the identified important properties of fresh and initially fouled SFDMs. Sludge deposition during SFDM formation appears to be dominated by permeate drag force and hydrophobic interaction, whereas the subsequent fouling rate turns out to be controlled by the content of eEPS, particularly carbohydrates, which significantly correlated with viscosity and SOUR.Graphical abstractHighlights► Effects of sludge properties on SFDM filtration characteristics were investigated. ► Large particles favor fast formation of fresh SFDMs with low filtration resistance. ► SFDM formation was dominated by permeate drag force and hydrophobic interaction. ► The content of eEPS, particularly carbohydrate, correlated with viscosity and SOUR. ► Initial fouling rate of SFDMs was mechanistically controlled by eEPS carbohydrate.

•GPP was used as a new activating agent to produce activated carbon.•AC-GPP contained much more total and basic groups than AC-PPA.•OCNH and CNH2 groups were effectively introduced onto the surface of AC-GPP.•AC-GPP showed higher Cd(II) sorption capacities than AC-PPA.•Sorption mechanisms: complexation, cation exchange and electrostatic attraction.The preparation of activated carbon (AC-GPP) from lotus stalks (LS) by guanidine phosphate (GPP) activation was studied, with a particular focus on the differences in the physical and chemical characterizations and Cd(II) sorption properties of AC-GPP and the activated carbon (AC-PPA) derived from phosphoric acid (PPA) activation of LS. The carbons were systematically examined by N2 adsorption/desorption, Boehm's titration, and FTIR and XPS analyses. The results of Boehm's titration showed that AC-GPP contained much more total and basic functional groups than AC-PPA. FTIR and XPS analyses revealed that NH2 and CONH groups were effectively introduced on AC-GPP's surface. Cd(II) sorption behaviors on AC-PPA and AC-GPP under different Cd(II) concentration, ionic strength and solution pH conditions were investigated. Although AC-PPA had much higher SBET than AC-GPP, its Cd(II) sorption capacity was 3–4 times less than AC-GPP per unit surface area. For the carbons, sorption isotherms at different ionic strength were very well described by the Langmuir model. According to the results of the sorption studies and XPS analysis, the surface complexation, electrostatic attraction and cation exchange between Cd(II) and O/N-containing functional groups on the carbons were the dominant mechanisms responsible for Cd(II) sorption.

Millions of tons of keratin wastes, including wool, hairs, horns, hooves and feather, are produced annually. They are almost pure keratin protein and hard degraded in environment. The use of keratin wastes as carbonaceous precursors for preparation of activated carbon could be a suitable method to solve the pollution. The paper presents the possibility of preparing activated carbon from keratin wastes (animal hairs, AH) and compares its physicochemical characteristics and sorption properties with the activated carbon derived from lignocellulose (cattail fibers, CF). Prior to activation at 500 °C for 1 h, AH and CF were dipped in phosphoric acid solution under two impregnation conditions: room temperature and pressure for 12 h (labeled as R) and high temperature and pressure for 20 min (labeled as H), producing R-AHAC, H-AHAC, R-CFAC and H-CFAC. R-AHAC and H-AHAC are mainly microporous, while R-CFAC and H-CFAC consist of a mix of micropores and mesopores. R-AHAC exhibits uneven carbonization and a much lower surface area than H-AHAC, while R-CFAC displays similar physicochemical properties to H-CFAC. H-AHAC shows higher (N+O+H) content, total acidic and basic functional groups and pH of point of zero charge than R-CFAC and H-CFAC. For H-AHAC and R-CFAC, sorption kinetics and isotherms of norfloxacin (NOR) and acetaminophen (ACP) agreed well with the pseudo-second-order model and Freundlich model. Additionally, with normalization of adsorbent surface area, sorption of NOR and ACP on H-AHAC was prominently higher than that on R-CFAC, which was attributed to their differences in physical and chemical characteristics.Highlights► Activated carbons were produced from keratin and lignocellulose materials. ► High temperature and pressure impregnating methods (100 °C and 0.1 MPa) were used. ► H-AHAC had lower surface area, but higher acidic and basic groups than R-CFAC. ► H-AHAC had lower NOR sorption, but higher ACP sorption than R-CFAC per unit gram. ► H-AHAC showed much higher NOR and ACP sorption than R-CFAC per unit surface area.

•Wool waste was used as the new material for activated carbon preparing.•Two heating methods: muffle furnace and microwave were used for preparation.•MFAC contained more total and basic groups than MAC.•MFAC exhibited much higher Ni(II) sorption capacities than MAC.•Sorption mechanisms: cation exchange and electrostatic attraction.The present study explored the utilization of wool waste (WW) for preparing activated carbon by muffle furnace (MFAC) and microwave (MAC) heating methods with phosphoric acid activation. MFAC was produced by activating at 550 °C for 40 min in muffle furnace. MAC was prepared with radiation power of 700 W and radiation time of 15 min. The physicochemical properties of the activated carbons were determined by N2 adsorption/desorption, Boehm's titration, and Fourier-transform infrared spectroscopy (FTIR). The sorption behaviors of the carbons toward Ni(II) were investigated through batch sorption experiments. MAC exhibited slightly larger surface area (519 m2/g) than MFAC (472 m2/g). However, results from Boehm's titration and FTIR suggested that MFAC contained more surface oxygen-containing functional groups than MAC. Sorption experiments indicated that MFAC presented better performance for Ni(II) sorption (17.87 mg/g) than MAC (6.09 mg/g). The sorption followed well the pseudo-second-order kinetic model and the sorption isotherms simulated well the Freundlich model for both of the carbons. Based on the physicochemical properties of activated carbons and the result of the sorption studies, oxygen-containing functional groups played an important role in the sorption of Ni(II). The likely important mechanisms for Ni(II) sorption onto MFAC and MAC were cation exchange and electrostatic attraction.The pore structures of the activated carbons by muffle furnace (MFAC) and microwave (MAC) heating methods presented high similarity while the sorption capacities of MFAC and MAC were quite different, which was ascribed to the differentiation in the content of surface oxygen-containing groups.

The present study explores the viability of using feathers to prepare activated charcoals with phosphoric acid activation. Feather-based activated charcoals (FACs) were produced by varying the weight ratio of phosphoric acid to feather (1.0–3.0) and activation temperature (500–600 °C). Porous texture, surface morphology, surface functional characteristics and chemical composition of FACs were analyzed by N2 adsorption/desorption, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and element analyzer. After activation, FACs presented well-developed micropore, favorable surface chemistry and high content of oxygen, nitrogen and hydrogen. These results indicated that keratin wastes could be used as a new source to produce activated charcoal.Highlights►Feather was used as a new source to produce activated charcoals. ► The activation temperature and weight ratio of H3PO4 to feather were studied. ► BET surface area, porous texture, SEM, FTIR and XPS of FACs were investigated.

In this paper, an activated carbon was prepared from Typha orientalis and then treated with KMnO4 and used for the removal of Basic Violet 14 from aqueous solutions. KMnO4 treatment influenced the physicochemical properties of the carbon and improved its adsorption capacity. Adsorption experiments were then conducted with KMnO4-modified activated carbon to study the effects of carbon dosage (250–1500 mg/L), pH (2–10), ion strength (0–0.5 mol/L), temperature, and contact time on the adsorption of Basic Violet 14 from aqueous solutions. The equilibrium data were analyzed by the Langmuir and Freundlich isotherms and fitted well with the Langmuir model. The pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to evaluate the kinetic data and the pseudo-second-order kinetics was the best with good correlation.KMnO4-modified activated carbon.

The effects of chemical oxygen demand (COD) concentration in the influent on nitrous oxide (N2O) emissions, together with the relationships between N2O and water quality parameters in free water surface constructed wetlands, were investigated with laboratoryscale systems. N2O emission and purification performance of wastewater were very strongly dependent on COD concentration in the influent, and the total N2O emission in the system with middle COD influent concentration was the least. The relationships between N2O and the chemical and physical water quality variables were studied by using principal component scores in multiple linear regression analysis to predict N2O flux. The multiple linear regression model against principal components indicated that different water parameters affected N2O flux with different COD concentrations in the influent, but nitrate nitrogen affected N2O flux in all systems.

To evaluate the ecological effects of lakeshore wetland rehabilitation on the eastern route of the South-to-North Water Transfer Project, species composition, coverage, height, and biomass of wetland communities at 22 sites of the study area on the shore of Nansi Lake in April and May 2007 were investigated. The wetlands under investigation were divided into platform fields, transition zones, and shallow water zones according to differences in elevations, water levels, and human activities. The species richness index, Shannon-Wiener index, Simpson index, and Pielou Evenness index were adopted to delineate and discuss the ecological effects of lakeshore wetland rehabilitation in 22 quadrates. Results showed that the species richness of the wetland areas after 2 years’ rehabilitation amounted to 47 of 24 families, higher than 25 of 20 families in areas without rehabilitation. The biodiversity index and abundance index of rehabilitated areas were also higher than those of platform fields and fish ponds where there was no rehabilitation. In addition, the Shannon-Wiener index, Simpson index, and community evenness index of platform fields in rehabilitated wetland areas were 1.619, 0.745, and 0.860, respectively, higher than those of the platform fields before rehabilitating. The results suggested that the constructed lakeshore wetland played an important role in protecting the diversity of species.

Nitrous oxide (N2O) is an important greenhouse gas and biological nitrogen removal process of wastewater treatment plant is one of its sources. Mechanisms of N2O emissions from anoxic–oxic biological nitrogen removal process were investigated and minimizations of N2O emissions were carried out from the aspect of organic carbon supplement, i.e., influent COD/NH4+ ratio (C/N ratio) and feeding strategy. Results showed that during anoxic–oxic biological nitrogen removal process, most of the N2O emissions occurred during the oxic phase, and both nitrifier denitrification and aerobic hydroxylamine oxidation pathways were possible mechanisms responsible for N2O emissions. N2O conversion rate decreased from 6.0% to 1.3% when the influent C/N ratio was increased from 7.5 to 14.5. This was mainly because of decrease in the abundance of Nitrosomonas-like ammonia oxidizing bacteria. Step feeding and external carbon source addition could reduce N2O conversion rate by 66.6% and 12.0%, respectively. Both of them were feasible methods for minimizing N2O emission from wastewater treatment process. The low N2O emission of step feeding was because of its high dissolved oxygen (DO) and low ammonium concentrations during the oxic phase, while the minimization effect of external carbon source addition was ascribed to its high nitrogen removal efficiency.

•A comprehensive index system for projects selection in EIPs is established.•Fuzzy Clustering Analysis is employed to simplify the comprehensive index system.•Weights of system indicators are obtained with Fuzzy Analytic Hierarchy Process.It is critical to extend and broaden the eco-industrial chain (EIC) by introducing new projects so that the stability of EIC network can be enhanced. At present, there is lack of effective control for project selection to eco-industrial park (EIPs) in China. This has led to low compatibility level of enterprises with the overall EIC network. By introducing the admission composite index, a framework is proposed in this study to assist the project selection in EIPs. It consists of three layers, i.e. target, criterion and variable. The preliminary index database is synthesized and simplified with Fuzzy Clustering Analysis (FCA). Fuzzy Analytic Hierarchy Process (FAHP) was employed to determine the weighting of each indicator. On the basis of the evaluation criteria, the evaluation method of the index system under two different conditions were established. This enriches the theory and methodology of ecological industry development in China. Meanwhile, the index system is effectively verified via an empirical case study. Results show that the index system is feasible, and quantitative results are consistent with the practice. These findings provide a good practical reference for the decision making of project selection in EIPs.Download high-res image (108KB)Download full-size image

Pressure-State-Response (PSR) model is one of the most commonly used models for environmental impacts assessment. As an effective tool for strategic management and performance evaluation, Balanced Scorecard (BSC) has been widely applied in the management field. PSR and BSC share the similar principles such as systematic, causality and sustainability oriented. Furthermore, BSC features equilibrium and dynamics. It is a feasible and innovative approach to establish a comprehensive environmental assessment framework by combining BSC and PSR. By placing the customer indicator on the top layer and following the PSR principle on the second layer, one model was designed to examine the impact of urbanization on the air environment in Shandong Province from 2005 to 2009 with factor component analysis. The results showed that urbanization and air environmental sustainability has been an upward trend in Shandong. The sustainable development level is low in Shandong presently, which provides a large potential for further improvement. This study is a useful reference for policy makers in terms of economic and environmental management.Graphical abstract.Download full-size imageHighlights► Balanced Scorecard is applied in the field of environmental impact assessment. ► A comprehensive environmental assessment framework by combining BSC and PSR. ► Principal factor analysis of the established indicators system.

Both long term and batch experiments were carried out to identify the sources of the N2O emission in anoxic/aerobic sequencing batch reactors (A/O SBRs) under different aeration rates. The obtained results showed that aeration rate has an important effect on the N2O emission of A/O SBR and most of the N2O was emitted during the aerobic phase. During the anoxic phase, nitrate ammonification was the major source of N2O emission while denitrification performed as a sink of N2O, in all three bioreactors. The N2O emission mechanisms during the aerobic phase differed with the aeration rate. At low and high aeration rates (Run 1 and Run 3), both coupled-denitrification and nitrifier denitrification were ascribed to be the source of N2O emission. At mild aeration rate (Run 2), nitrifier denitrification by Nitrosomonas-like ammonia oxidizing-bacterial (AOB) was responsible for N2O emission while coupled-denitrification turned out to be a sink of N2O because of the presence of inner anaerobic region in sludge flocs.