•Fe2O3/ACF hybrid was rapidly fabricated using a microwave-assisted heating strategy.•Fe2O3 nanorods in sizes of 20 × 50 nm were homogeneously anchored on the surface of ACF.•The maximum adsorption capacity of 20.33 mg g−1 As (V) on Fe2O3/ACF was achieved.•The adsorption of As (V) is an endothermic process (ΔH0 = 24.79 kJ mol−1).•The presence of salt shows little effect on the adsorption of As (V).In this paper, an efficient adsorbent, iron-modified activated carbon fiber (Fe2O3/ACF), was rapidly fabricated by microwave-assisted heating treatment strategy, which is used to remove As(V) from simulated wastewater. The adsorbent was characterized by scanning electron microscopy (SEM), TEM, N2 sorption, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The characterization results showed that rod-like Fe2O3 particles in sizes of about 20 nm × 50 nm were homogeneously anchored on the surface of ACF. The goal of high As(V) removal efficiency was achieved with maximum adsorption capacity of 20.33 mg g−1. The effects of temperature on thermodynamics and kinetics of As(V) adsorption were systematically studied. It was found that the adsorption of As(V) on the surface of Fe2O3/ACF is an endothermic process with a standard enthalpy change (ΔH0) of 24.79 kJ mol−1. Batch experimental result showed that almost all of the As(V) with initial concentration of 3.0 mg L−1 can be removed in the presence of Fe2O3/ACF, where the residual As(V) in filtrate was less than 0.01 mg L−1, below the tolerance level of drinking water suggested by World Health Organization (WHO). The presence of salt such as NaCl, Na2SO4, and MgSO4 showed little effects on the adsorption of As(V), indicating the promising application of Fe2O3/ACF in industrial wastewater.

•Develop a multi-start distributor for As removal by sulphide precipitation.•Pilot and industrial scale tests exhibited efficient As removal.•The sludge volume was one fifth of that from the traditional lime–FeSO4 process.Chronic Arsenic (As) poisoning has become a worldwide issue of public health. Therefore, efficient removal of As from wastewater before drainage is of great importance. This paper aimed at designing a novel reactor containing an immersed multi-start distributor for sulphide feeding to remove As from dirty acid wastewater by precipitation. The experimental results showed that, by using this novel device, an improved performance of sulphide precipitation was achieved even at stoichiometric molar ratio of sulphide and arsenic. By combining this novel sulphide feeding process with lime–FeSO4 precipitation to treat dirty acid wastewater in industrial scale, the residual concentrations of As and other heavy metals (Cu, Cd and Pb) in effluent are below the discharge standard specified by the Chinese government(GB 3838-2002).

•Novel PNP-distillation strategy was put forward in recovery of HAc from waste acid.•Pure HAc with a recovery rate of 94.3% was obtained under optimal condition.•This strategy has the merits of being simple, reproducible, and easy to scale-up.In recent years, attention on treatment of industrial waste acids has been increasing considerably due to enforcement of the environmental regulations as well as economical considerations about the waste acids. In this paper, a novel approach for recovery of acetic acid (HAc) from electronic industrial waste acids, containing about 58 wt.% of HAc, 39 wt.% of nitric acid (HNO3), 3 wt.% of phosphoric acid (H3PO4), and small amount of hydrochloride acid (HCl) and hydrofluoride acid (HF), was developed using partial neutralization pretreatment (PNP)-distillation strategy. The effects of distillation time, types of alkali for neutralization and oil bath temperature on recovery of HAc were systematically studied. It was found that HAc can be efficiently recovered from the waste acids with a yield of 94.3% (purity 99.4%) under optimal conditions. The treatment scheme for HAc recovery from waste acids is featured by feasibility, reproducibility and massive productivity.Graphical abstract

•A novel three-stage process is proposed for disposal the dirty acid wastewater.•CaCO3 could be used as more suitable neutralizer than others in 1st stage.•The gypsum by CaCO3 has higher crystal purity and can be reused.•The effect of CO32− in the 2nd stage can be ignored.To solve the environmental problems caused by dirty acid wastewater discharging from sulfuric acid plant, this study developed an efficient and economical method to remove arsenic from dirty wastewater through a continuous three-stage co-precipitation processing, which includes (1) formation of gypsum by addition of calcium carbonate, (2) neutralization of the filtrate with lime, and (3) adsorption of residual arsenic by ferric sulfate. In the 1st stage, the gypsum formed from using CaCO3 showed higher crystal purity than those using traditional neutralizers such as CaO and Ca(OH)2, and the precipitates are recyclable due to the fact that carbon dioxide (CO2) emitted in neutralization could prevent gypsum from shielding the surface of the neutralizer. In the 2nd stage, Ca(OH)2 was used to get a pH of 11.9 for arsenic removal. CO32− shows little effect on arsenic removal rate and stability of precipitates. In the 3rd stage, Fe2(SO4)3 was utilized to further remove arsenic to make the its concentration below than 0.2 mg/L by adsorption at pH 9.0. Using this novel 3-stage processing, the gross weight of As-containing hazardous waste was sharply reduced to as high as 50%. The high purity of the obtained As-containing solid waste makes it possible to be reused as a raw material.