Changsheng Peng

Recovery of copper and water from copper-electroplating wastewater by the combination process of electrolysis and electrodialysis

In this paper, a laboratory-scale process which combined electrolysis (EL) and electrodialysis (ED) was developed to treat copper-containing wastewater. The feasibility of such process for copper recovery as well as water reuse was determined. Effects of three operating parameters, voltage, initial Cu(2+) concentration and water flux on the recovery of copper and water were investigated and optimized. The results showed that about 82% of copper could be recovered from high concentration wastewater (HCW, >400mg/L) by EL, at the optimal conditions of voltage 2.5 V/cm and water flux 4 L/h; while 50% of diluted water could be recycled from low concentration wastewater (LCW, <200mg/L) by ED, at the optimal conditions of voltage 40 V and water flux 4 L/h. However, because of the limitation of energy consumption (EC), LCW for EL and HCW for ED could not be treated effectively, and the effluent water of EL and concentrated water of ED should be further treated before discharged. Therefore, the combination process of EL and ED was developed to realize the recovery of copper and water simultaneously from both HCW and LCW. The results of the EL-ED process showed that almost 99.5% of copper and 100% of water could be recovered, with the energy consumption of EL ≈ 3 kW h/kg and ED ≈ 2 kW h/m(3). According to SEM and EDX analysis, the purity of recovered copper was as high as 97.9%.

Elimination of Cr(VI) from electroplating wastewater by electrodialysis following chemical precipitation

Abstract In this work, the elimination of Cr(VI) from an electroplating wastewater in China was studied by chemical precipitation (CP), electrodialysis (ED), and their combination. The experimental results show that CP was effective as a rougher treatment for removing Cr(VI) from a high Cr(VI) wastewater, but not for a deep Cr(VI) elimination. ED alone failed to achieve a deep Cr(VI) elimination from a high Cr(VI) wastewater, although it was very effective for a medium Cr(VI) wastewater. The mechanism might be attributed to the sedimentation of chromatic ions as polychromates in the pores of ED membranes because of high Cr(VI) concentration in wastewater, which may block the pores and thus stop the transportation of the ions through the pores. It was found that the combined chemical precipitation and electrodialysis (CP + ED) process is an effective and economic process to treat high Cr(VI) electroplating wastewater. This process allows treated water to be completely recycled to electroplating lines, fewer environmental concerns, and lower reagent and operation costs.

Citric acid facilitated thermal treatment: An innovative method for the remediation of mercury contaminated soil

Thermal treatment is a promising technology for the remediation of mercury contaminated soils, but it often requires high energy input at heating temperatures above 600°C, and the treated soil is not suitable for agricultural reuse. The present study developed a novel method for the thermal treatment of mercury contaminated soils with the facilitation of citric acid (CA). A CA/Hg molar ratio of 15 was adopted as the optimum dosage. The mercury concentration in soils was successfully reduced from 134 mg/kg to 1.1mg/kg when treated at 400°C for 60 min and the treated soil retained most of its original soil physiochemical properties. During the treatment process, CA was found to provide an acidic environment which enhanced the volatilization of mercury. This method is expected to reduce energy input by 35% comparing to the traditional thermal treatment method, and lead to agricultural soil reuse, thus providing a greener and more sustainable remediation method for treating mercury contaminated soil in future engineering applications.

Adsorption of As(V) inside the pores of porous hematite in water.

As(V) adsorption inside the pores of porous hematite in water has been studied in this work. This study was performed on nonporous hematite and porous hematite prepared from the thermal decomposition of goethite and siderite through the measurements of adsorption isotherm, SEM-EDX, XRD and BET. The results demonstrated that the As(V) adsorption was difficult to be realized inside pores if they were too small. This observation might be due to that the pore entrances were blocked by the adsorbed ions and thus the inside surfaces became invalid for the adsorption. Only if the pore size is large enough, the effective surface area inside pores would be close to that on non-porous hematite for As(V) adsorption. In addition, it was found that siderite is better than goethite for preparing porous hematite with thermal decomposition as adsorbent for arsenic removal.

Viscosities of Binary and Ternary Mixtures of Water, Alcohol, Acetone, and Hexane

This articles studied and determined the viscosities of the binary mixtures of water–methanol, water–ethanol, water–propanol, water–acetone, acetone–ethanol, methanol–ethanol, and acetone–hexane and the ternary mixtures of water–methanol–ethanol and water–ethanol–acetone at 20°C. It is shown that the mixing of water with the alcohols and acetone resulted in a positive deviation of viscosity, which reached the maximum value at the water mole fraction x 1 ∼ 0.7 for water–methanol, x 1 ∼ 0.72 for water–ethanol, x 1 ∼ 0.74 for water–propanol, and x 1 ∼ 0.83 for water–acetone binary mixture. This viscosity deviation can be mainly attributed to the formation of micelles of alcohol or acetone molecules in water because of the hydrophobic attraction between the hydrocarbon chains. The micelle surfaces are surrounded by hydration layers, leading to the positive viscosity deviation in the liquid mixtures because the water in hydration layers has a much higher viscosity than bulk water. Also, the contrary observation was found in the binary mixtures of acetone–ethanol and acetone–hexane, having a negative viscosity deviation.

Thickness of Solvation Layers on Nano‐scale Silica Dispersed in Water and Ethanol

In this work, the thickness of solvation layers on nano‐scale silica dispersed in water, ethanol, and water‐ethanol mixture (1∶1 by volume) have been determined with the viscosity method, which is based on the Einstein equation of viscosity of dispersion. This determination was carried out on a nano‐scale silica with the specific surface area of 189 m2/g through the measurements of relative viscosity of the silica dispersion as the function of volume fraction of the dry silica in the dispersion. The experimental results and the calculations showed that the thickness of the solvation layer on the nano‐scale silica was 12.8 nm in water, 11.9 nm in ethanol, and 13.2 nm in the water‐ethanol mixture. The results suggest that water‐ethanol mixture (1∶1 by volume) should be used as the liquid medium in order to prepare a high stability nano‐scale silica suspension.

ELECTRO-REGENERATION MECHANISM OF ION-EXCHANGE RESINS IN ELECTRODEIONIZATION

The regeneration mechanism of ion-exchange resins in the electrodeionization process has been studied with theoretical and experimental investigation. Theoretically, contact forms of resins and membranes can be divided into 4 types, and the possible places of water-splitting are located at the contact faces of different types resins and membranes, for example, cation ion-exchange resins contact with anion ion-exchange resins or membranes, anion ion-exchange resins contact with cation ion-exchange resins and membranes, according to the theoretical calculation. And the exhausted ion-exchange resins can be regenerated by the electrodeionization process with the regeneration efficiency at 70–80% in this work.

DETERMINATION OF THICKNESS OF HYDRATION LAYERS ON MICA IN AQUEOUS SOLUTIONS BY USING AFM

We present an experimental technique to determine the thickness of hydration layers on solid surfaces in aqueous solutions by using an atomic force microscope (AFM). This technique is based on the phenomenon where a small line bending in the AFM force–distance plot of hydrated solid surface in aqueous solutions, may be due to the existence of hydration layers on the tip and the solid surface. The thickness of hydration layers on mica plate immersed in water and NaCl solutions were determined with this technique.

Phytogenic magnetic nanoparticles for wastewater treatment: a review

Presently, there is an emerging research trend in the fabrication of Phytogenic Magnetic Nanoparticles (PMNPs) and their applications in the water/wastewater treatment (WWT), due to their dynamic morphology, desired size, super paramagnetic behavior and high saturation magnetization value. Green fabrication of PMNPs is clean, non-toxic, eco-friendly, fast and cost-effective as compared to other physico-chemical technologies, which make it a promising technology. However, certain aspects such as the optimization of the fabrication protocol in order to produce desired quality of PMNPs, regeneration and reusability, are the main hindrances in the transfer of this technology from the laboratory scale to the commercial applications. Therefore, the present study highlights the performance of PMNPs for the removal of aqueous pollutants from wastewater. In addition, the research developments of PMNPs regarding fabrication mechanism, regeneration and reusability for WWT are discussed. The study also provides a model of PMNPs based on zero effluent discharge and consequently, the WWT process is proposed. Finally, future perspectives and challenges are discussed to make PMNPs based green nanotechnology technically more feasible and economically sustainable.

Yield cultivation of magnetotactic bacteria and magnetosomes: A review

Magnetotactic bacteria (MTB) have started to be employed for the biosynthesis of magnetic nanoparticles, due to the rapidly increasing demand for nanoparticles in biomedical, biotechnology and environmental protection. MBT are the group of prokaryotes that have the ability to produce bio‐magnetic minerals or bio‐magnetic crystals of either magnetite (Fe3O4) or greigite (Fe3S4) in numerous shapes and size ranges, known as magnetosomes (MS). MS compel MTB to respond to the applied external magnetic field. However, it is extremely difficult to grow MTB and produce high yield of MS under artificial environmental conditions, thus creating a major hurdle to relocate MTB technology from laboratory scale to industrial or commercial level. Therefore, to best of our knowledge this review is the first attempt to highlight existing research developments about the laboratory scale and mass production of MS by MTB. Moreover, the optimum culture media and environmental conditions used for the cultivation of MTB were also considered. Finally, future research is encouraged for the improvement of MS yield which will result in the development of advanced nanotechnology/magnetotechnology.