Yude Shu

Study of arsenic(V) adsorption on bone char from aqueous solution.

Arsenic is a toxic element and may be found in natural waters as well as in industrial waters. Leaching of arsenic from industrial wastewater into groundwater may cause significant contamination, which requires proper treatment before its use as drinking water. The present study described the removal of As(V) on bone char in batch studies conducted as a function of pH, dosage of adsorbent, and contact time. Kinetics revealed that uptake of As(V) ion by bone char was very rapid in the first 30min and equilibrium time was independent of initial As(V) concentration. And the adsorption process followed a first-order kinetics equation. The arsenic removal was strongly dependent on pH and dosage of adsorbent. Fourier transform infrared spectra of bone char before and after As(V) adsorption demonstrated that Ca-OH functional group plays an important role for As(V) ions removal, and the mechanisms of the removal of As(V) on bone char was complex mechanism where both co-precipitation and ion exchange. The results suggested that bone char can be used effectively for the removal of As(V) ion from aqueous solution.

Treatment of nickel-ammonia complex ion-containing ammonia nitrogen wastewater

Air stripping was adopted to treat nickel ammonia complex ion-containing wastewater in order to remove nickel and ammonia simultaneously in one technological process. The relationship among pH, the concentration of nickel ammonia complex ion and total ammonia concentration was analyzed theoretically. Influence of pH value, water temperature, airflow rate and time on air stripping was studied in detail by static experiment in laboratory. The results show that at pH 11, temperature of 60 ℃ and airflow rate of 0.12 m 3 /h, NH3 and Ni 2+ concentrations remained in wastewater are less than 2 and 0.2 mg/L, respectively, after blowing for 75 min, which reaches the standard of the state discharge. When the tail gas is absorbed by 0.5 mol/L H2SO4 in order to avoid the

Degradation of organic wastewater containing Cu–EDTA by Fe–C micro-electrolysis

Abstract In order to break the complex bonds and treat the organic wastewater containing heavy metal, such as Cu–EDTA solution, a novel process of Fe–C micro-electrolysis was proposed. Based on the principle of iron-carbon micro-electrolysis reaction, OH radicals which were generated under the acidic aerobic condition during the micro-electrolysis process attacked to the organic groups of coordination compounds, which resulted in complex bonds breaking. Therefore copper (II) ions were removed via nascent gelatinous ferric hydroxide and ferrous hydroxide, and EDTA was degraded by OH radicals. Effects of pH value, temperature, electrolysis time and mass ratio of Fe to C on residual concentrations of total organic carbon (TOC) and Cu(II) were studied. The mechanism of Fe–C micro-electrolysis was investigated and verified by analyzing micrographs of scanning electron microscopy (SEM), energy dispersive analysis (EDS) and Fourier transform infrared spectrometry (FTIR). The removal efficiency is optimal at pH value of 2.0, temperature of 25 °C, the mass ratio Fe to C of 0.02, and reaction time of 60 min. Under above conditions, the concentration of TOC decreases from 200 mg/L to 40.66 mg/L and the residual concentration of Cu(II) decreases from initial 60 mg/L to 1.718 mg/L.

Equilibrium of hydroxyl complex ions in Pb2+-H2O system

Abstract The thermodynamics equilibrium principle was used to construct the diagrams for the concentration of complex ions (pc) vs pH, the distribution ratio of lead hydroxyl complex ions (αn) vs pH, and the conditional solubility product of Pb(OH)2 vs pH in the Pb2+-H2O system. The relationship between the equilibrium concentration of each kind of lead hydroxyl complex ions in equilibrium with Pb(OH)2(s) and pH value was shown in the system. The minimum solubility of lead is at the pH value of 10.096–10.997. The distribution ratio of each kind of the lead hydroxyl complex ions is determined as a function of the pH value and the total lead concentration ([Pb]T). The diagram for the conditional solubility product, pKSP vs pH, shows that each kind of lead hydroxyl complex ions existing in the system is dependent upon an optimized pH value at the established concentration of [Pb]T, and that pKSP reaches the minimum at the pH value of 10.3–11.2. The results can provide a theoretical basis for removing lead ions from wastewater by the neutralization and hydrolyzation technology.

Biological preparation and application of poly-ferric sulfate flocculant

Abstract A novel inorganic polymer flocculant, poly-ferric sulfate (BPFS) was prepared by oxidation of ferrous sulfate using domestic Thiobacillus ferrooxidans ( T·f ) under acid condition. The optimal conditions for the preparation were pH value of 1.5, (NH 4 ) 2 SO 4 dosage of 0.5 g/L, initial Fe 2+ concentration of 45g/L, inoculum 10%, rotating speed of 120 r/min, reaction time of 5-6 d and reaction temperature of 30 °C. Under the optimal conditions, the BPFS product with pH value of 1.5-2.2, basicity of 17.5%-22.7% and total iron content of 43.87-45.24 g/L was obtained. The application of the BPFS to three wastewaters was carried out, and the removal efficiencies of COD, decolorization and Zn 2+ by BPFS can be reached 70%, 90% and 99%, respectively. The result suggests that the BPFS is an excellent flocculant for water treatment.

Effect of impurities in recycling water on Pb-Ag anode passivation in zinc electrowinning process

Abstract Effect of impurities in recycling water on Pb-Ag anode passivation in zinc electrowinning process was investigated by linear scan voltammetry. Results show that passivation process would be affected in the presence of Cl − and F − in recycling water. It was highly advantageous to take H 2 SO 4 concentration as 180 g/L, Mn 2+ concentration as 3-5 g/L and F − less than 42 mg/L. However, passivation process would not be affected when Cl − concentration was less than 13 mg/L without any other ions, or when mass ratio of Mn 2+ to Cl − existing in electrolyte was 8, where Cl − concentration could reach up to 625 mg/L.

Regeneration of activated carbon adsorbed EDTA by electrochemical method

Abstract Activated carbon after saturated adsorption of EDTA was used as particle electrode in a three-dimensional electrode reactor to treat EDTA-containing wastewater. Electrochemical method was used to regenerate activated carbon after many times of electrolysis. Based on the analysis of infrared spectra of activated carbon after adsorption and repeated electrolysis, EDTA was degraded into glycine, and then non-catalytic activated associated complex was formed with N—H bond on the activated carbon. The catalytic ability of the activated carbon vanished and the EDTA degradation efficiency was dropped. Activated carbon could be effectively regenerated by electrochemical method in the three-dimensional reactor. Effects of electric current, conductivity and pH on activated carbon regeneration were investigated, and the optimum conditions were concluded as follows: 100–300 mA of current intensity, 1.39 mS/cm of electric conductivity, 60 min of electrolysis time and pH 6.0-8.0. Under the optimized conditions, the activity of the activated carbon can be recovered and the residual total organic carbon (TOC) was below 10 mg/L (the initial TOC was 200 mg/L) in the three-dimensional electrode reactor.

Phase equilibrium of CaSO4–Ca(OH)2–H2O system

Abstract In order to provide the theoretical guidance for applying the neutralization method to treatment of heavy metals wastewater with high concentration of sulfate, and to better understand the mechanism of calcium sulfate scale formation, the equilibrium solubility data of CaSO 4 –Ca(OH) 2 –H 2 O system at 298.15 K were theoretically calculated via the Pitzer semi-empirical ion-interaction theory, and determined experimentally by the optical method combining with X-ray diffractometry, and the calculated and determined phase diagrams of CaSO 4 –Ca(OH) 2 –H 2 O system were plotted and compared. Physical definition of each area was studied, and the physical law of characteristic point and line was explained in detail. Adjusting the pH value of neutralization-hydrolysis solution depended on the SO 4 2- concentration in the system. And interaction characteristics between the solubilities of CaSO 4 (s) and Ca(OH) 2 (s) were found out.

Thermodynamic equilibrium of CaSO4-Ca(OH)2-H2O system

Abstract The p c —pH diagrams of the CaSO 4 -Ca(OH) 2 -H 2 O system and its two subsystems at 298.15 K were constructed according to the theory of thermodynamic equilibrium. The interaction characteristics between the solubility of CaSO 4 (s) and Ca(OH) 2 (s) can be found out from the diagrams. CaSO 4 (s), Ca(OH) 2 (s) and solution coexist when the pH value of solution is about 13.2. CaSO 4 (s) with the minimum solubility of 0.411 g/L is in equilibrium with solution when the pH value is lower than 13.2, and Ca(OH) 2 (s) with the minimum solubility of 2.749 g/L is in equilibrium with solution at the pH value over 13.2, which provides a theoretical basis for the treatment and reuse of industrial wastewater, especially for the wastewater containing sulfate which can be treated by lime-milk neutralization.

Leaching and recycling of zinc from liquid waste sediments

Abstract The selective leaching and recovery of zinc in a zinciferous sediment from a synthetic wastewater treatment was investigated. The main composition of the sediment includes 6% zinc and other metal elements such as Ca, Fe, Cu, Mg. The effects of sulfuric acid concentration, temperature, leaching time and the liquid-to-solid ratio on the leaching rate of zinc were studied by single factor and orthogonal experiments. The maximum difference of leaching rate between zinc and iron, 89.85%, was obtained by leaching under 170 g/L H2SO4 in liquid-to-solid ratio 4.2 mL/g at 65 °C for 1 h, and the leaching rates of zinc and iron were 91.20% and 1.35%, respectively.