To use copper ferrocyanide (CuFC) more efficiently in wastewater treatment, the method of isotope carrying used in 137Cs removal was investigated. A calculation model based on Freundlich isotherm was established to determine the optimum initial cesium concentration, at which the highest decontamination factor (DF) could be obtained at a certain CuFC dosage. An accurate DF prediction model was developed to describe synergistic effects of sodium and potassium. A novel index called volumetric distribution coefficient (Kvd) was proposed to evaluate adsorption performance in terms of DF and concentration factor.

•A novel integrated PR-MS system was developed to remove I− efficiently at lab-scale.•Possible reactions were presented and I− was transferred to CuI(s) in the PR.•The addition of Na2SO3 played an important role in the protection of Cu+.•Solid-liquid separation and copper removal were simultaneously attained in the MS.A novel integrated precipitation reactor (PR) and membrane separator (MS) system was developed for the removal of radioactive I− from simulated liquid waste. The PR-MS system was evaluated at the lab-scale, the I− removal efficiency reached approximately 97.0% and the concentration factor (CF) value was 1050 when the concentration of added Na2SO3 was 40 mg/L and the CuCl dosage was 260 mg/L. The addition of Na2SO3 played an important role in the removal of dissolved oxygen (DO) and the formation of CuI. These reactions, including the oxidation of SO32−, the dissociation of CuCl, the disproportionation of Cu+, and the formation of CuI and Cu2O, occurred in the PR. Furthermore, the influence of the concentration of added CO32− on copper removal was investigated, and solid-liquid separation and copper removal were simultaneously attained in the MS. The I− removal efficiency gradually decreased from 97.0% to 58.5% and the Cu2+ concentration in the effluent decreased from 18.71 mg/L to 0.719 mg/L with the addition of CO32− at a concentration that ranged from 0 to 80 mg/L. Experimental results show the PR-MS system is of great potential for industrial application on treatment of liquid waste contaminated with radioactive I−.

This paper aimed to investigate the occurrence and concentrations of emerging and priority pollutants in the municipal reverse osmosis concentrate (ROC) using liquid–liquid extraction (LLE) followed by gas chromatography-mass spectrometry. The results indicated that there were varieties of pollutants, including chlorinated organic compounds, polycyclic aromatic hydrocarbons (PAHs), phthalate esters (PAEs), pharmaceutical and personal care products (PPCPs), herbicides and flame retardants, in the ROC. Most of the pollutants were quantified, and the performance of the analytical method was explored. For most of the target compounds, the mean recoveries at two concentration levels (0.17 μg L−1 and 1.67 μg L−1) ranged from 70% to 130% and the relative standard deviation (RSD) values were less than 20%, indicating excellent accuracy and precision. Typical concentrations of most of the pollutants were as low as tens or hundreds of ng L−1, whereas others were as high as several μg L−1 (such as, the concentration of 2-chloroethyl ether was 1.42 μg L−1, of caffeine was 3.73 μg L−1, and of benzyl butyl phthalate was 4.90 μg L−1).

•Organics was removed efficiently from the RO concentrate by the process.•PAC dose was significantly less than that of the single-stage adsorption process.•A calculation method correlating the effluent quality and PAC dose was feasible.•Lower dilution factor needed lower PAC dose, but aggravated membrane fouling.A powdered activated carbon (PAC) accumulative countercurrent two-stage adsorption–microfiltration hybrid process was investigated for the removal of organics from the reverse osmosis concentrate (ROC) produced in a refinery wastewater treatment plant. The results showed that approximately 70% of DOC was removed from the ROC; the effluent met the reverse osmosis (RO) influent quality requirement and could be further reclaimed by an RO system to improve the overall recovery rate by more than 90%; and >40% of the PAC dose was reduced compared to that in the conventional single-stage adsorption process. A calculation method for correlating the effluent quality with the PAC dose was calibrated, and the validity of the method was confirmed by a deviation of <5%. The dilution factor (F) affected the PAC dose and membrane fouling. The PAC dose at F = 0.3 was 14.46% lower than that at F = 0.5 based on the same effluent quality, but the membrane fouling was more severe in the former case. Analyses of the membrane eluent and SEM-EDS demonstrated that fine PAC particles adhering to the membrane surface and blocking the membrane pores dominated the irreversible membrane fouling process. Good correlations (R2 > 0.95) between the UV254 and DOC of the effluent could facilitate the operation monitoring of the process.

•A PAC countercurrent four-stage adsorption/MF hybrid process was developed.•PAC consumption was further reduced compared with that in two-stage adsorption.•Calculation method correlating PAC dose and organic removal was established.•Membrane fouling was mitigated compared with that in two-stage adsorption.In this study, in order to reduce the impact of reverse osmosis concentrate (ROC) on the receiving body of water and/or improve the recovery rate of reverse osmosis (RO) system by reusing the treated ROC as a feeding, a powdered activated carbon (PAC) countercurrent four-stage adsorption/MF hybrid process was developed for organic removal from ROC. The process could achieve good organic removal at lower PAC consumption. For dissolved organic carbon (DOC) removal efficiency of 70.0%, the PAC dose was 21.6% less than that in countercurrent two-stage adsorption and 50.9% less than that in single-stage adsorption. The calculation method for correlating removal efficiency and PAC dose was deduced and validated. The validation result showed that the relative error between the average experimental DOC removal efficiency and the calculated one was less than 5% throughout the experiment, exhibiting good accuracy for the calculation method. Compared with countercurrent two-stage adsorption, the membrane fouling in the new process could be mitigated to a certain extent. The total number of sub-cycles in a cycle (n) influenced the hydraulic retention time (HRT) and the total volume of the reactors. Results showed that the HRT increased as n increased.

•The wet oxidation regeneration of PAC used for ROC treatment was evaluated.•The relative adsorption amount of PAC regenerated optimally could reach 0.65.•The mass balance principle for carbon was proposed for regeneration evaluation.•The regenerated PAC under optimum condition mostly remove organics with MW < 1 kDa.The wet oxidation (WO) regeneration of powdered activated carbon (PAC) used for reverse osmosis concentrate (ROC) treatment was studied. The exhausted PAC was regenerated at different temperatures and times. The experimental results indicated that the optimum regeneration condition could be achieved at a temperature of 200 °C for 60 min. The mass of carbon in the solid, gas and liquid phases before and after the PAC regeneration was balanced in different regeneration conditions. A molecular weight (MW) distribution of organic matter (OM) in the effluent treated by the PAC regenerated at optimum conditions was performed.Download high-res image (217KB)Download full-size image

•A countercurrent two-stage adsorption–microfiltration (CTA-MF) process was proposed.•Dissolved organics in petrochemical RO concentrate were removed efficiently.•A high overall recovery (91%) of reverse osmosis (RO) can be achieved.•A simple CTA-MF calculation method was established to predict the effluent.In petrochemical wastewater reclamation, the dissolved biorefractory organics from reverse osmosis concentrate (ROC) is a key obstacle to increasing the overall recovery of reverse osmosis (RO) technology. A hybrid process of countercurrent two-stage adsorption and microfiltration (CTA-MF) was proposed to remove the organics in ROC by powdered activated carbon (PAC). In order to analyze the CTA-MF process, a simple calculation method was established based on the adsorption accumulation principle and response surface methodology (RSM) equations. Approximately 37% of fresh PAC was saved through the CTA-MF process compared with a conventional adsorption process. When the fresh PAC dosage was 0.48 g/L, the average values of chemical oxygen demand (COD) and dissolved organic carbon (DOC) were decreased from 94.1 mg/L and 25.6 mg/L to 36.9 mg/L and 6.98 mg/L, respectively, which coincided well with the predicted results and met the influent requirement of RO for high overall recovery.

This paper aimed to investigate the occurrence and concentrations of emerging and priority pollutants in the municipal reverse osmosis concentrate (ROC) using liquid–liquid extraction (LLE) followed by gas chromatography-mass spectrometry. The results indicated that there were varieties of pollutants, including chlorinated organic compounds, polycyclic aromatic hydrocarbons (PAHs), phthalate esters (PAEs), pharmaceutical and personal care products (PPCPs), herbicides and flame retardants, in the ROC. Most of the pollutants were quantified, and the performance of the analytical method was explored. For most of the target compounds, the mean recoveries at two concentration levels (0.17 μg L−1 and 1.67 μg L−1) ranged from 70% to 130% and the relative standard deviation (RSD) values were less than 20%, indicating excellent accuracy and precision. Typical concentrations of most of the pollutants were as low as tens or hundreds of ng L−1, whereas others were as high as several μg L−1 (such as, the concentration of 2-chloroethyl ether was 1.42 μg L−1, of caffeine was 3.73 μg L−1, and of benzyl butyl phthalate was 4.90 μg L−1).