Advanced Materials Research Vols. 634-638

Abstract: The unique morphology and structure of carbon nanotubes (CNTs) keep attracting a great number of researchers to explore the novel properties of these materials. The special structure of CNTs determines its physical and chemical properties, mainly reflected in its novel electrical, mechanical properties and excellent adsorption performance. This review summarizes the adsorption properties of CNTs and their properties related to the adsorption of various heavy metal ions, organic and inorganic pollutants from large volumes of aqueous solutions. CNTs is a kind of potential environmental material. This article also put forward future opportunities for CNTs application in environmental systems.

Abstract: Alumina red mud from aluminum industry has not been utilized effectively due to its strong alkaline, and SO₂ is an industrial pollutant which mainly produced by thermal power plants. For the comprehensive utilization of waste, the mineral component, chemical composition, grain size and microstructure of alumina red mud from Henan Branch of China Aluminum Co. were determined in this research. Thermodynamics analysis of FGD related desulfurization mechanism was studied as well. The self-designed glass absorption device 1700×60mm with its accessories was installed on-the-spot of Zhengzhou Xinli Electric Power Company Limited. The cyclic absorption experiments were conducted and the influential factors such as liquid-solid ratio (R_L/S), empty tower gas velocity (V(SO₂)), SO₂ concentration (c(SO₂)), and liquid-gas ratio (R_L/G) were examined through the orthogonal tests. The maximum efficiency of FGD is 97.5% under the optimal conditions: R_L/S is 7:1 (g/g), V(SO₂)is 0.35m/s, c(SO₂) is 1700mg/m³ and R_L/G is 12:1 (L/m³).

Abstract: Removal effect of NH3-N by chemical precipitation process was studied in treating excess sludge liquor (the NH3-N concentration 600~1000mg/L) produced from a municipal wastewater treatment plant. MgSO4 and Na2HPO4 were used as the precipitants to investigate the influences of initial pH, reaction time and the precipitants dosage on the NH3-N removal effect as well as the concentration of residual TP. Results showed that with the initial pH of 11.0, reaction time of 10min, and the additional ratio of precipitants being Mg:N:P＝1.0:1.0:1.0, over 90% NH3-N removal efficiency was achieved which would significantly facilitate the subsequent biological treatment process.

Abstract: Affects of thiosulfate (S₂O₃^2-) and sulfate (SO₄^2-) on determination of thiocyanate (SCN^-) in desulfurization waste solution (DWS) by spectrophotometry were investigated. The experiment results suggested that S₂O₃^2- and Fe3+ generated purple compound [Fe(S₂O₃)₂]^- which has a strong absorption at 450nm, but the purple soon fades in this process. As long as the reacting time is longer than 120s, the impact of S₂O₃^2- can be eliminated. In addition, sulfate has no effect. At 450nm wavelength, linear relationship between concentration of SCN^- and absorbance was C=19.7272A-0.2774, which conformed to the Beer Law in the range of 2.00 ~ 19.45μg•ml^-1, the correlation coefficients was 0.9996. The Fe³⁺-SCN^- spectrophotometric method of monitoring SCN- in desulfurization waste solution was feasible.

Abstract: Recovery of iron from the waste slag is of great interest for maximum use of mineral resource, reduction of environment impact and improvement of economical benefits to the related companies. This paper is mainly focused on the effect of the temperature on recovery of iron from waste slag of pyrite processing using reduction-roasting magnetic separation method. The experimental results show that under the treatment condition in this work about 70% of the iron was recovered from the waste slag, where the iron content in the concentrate is 57%. After the further treatment with chlorinated segregation-magnetic separation, the iron content in the recovered slag can reach 83%

Abstract: The disposal of acid wastewater generated by a copper-nickel smelting enterprise by using abandoned tailings mortar combined with sulfide precipitation and coagulation indicated that this method has demonstrated good results: the effluent can acheive “Emmission standard of pollutants for copper, nickel, cobalt industry” (GB 25476-2010); the heavy metals in the sediment is not apt to experience dissolution, thus less possible for secondary pollution of soil and groundwater. The optimal combination conditions of this process for sludge/wastewater mass ratio is 14:1; sodium sulfide’s dosing is 20 ml, reaction time is 20 min; FeSO4 and acid waste water volum ratio is 0.05, the reaction time is 30 min.

Abstract: The electrochemical oxidation of 4-chlorophenoxyacetic acid on Ti/SnO2-Sb2O5/PbO2 electrode was studied by cyclic voltammetry in this paper. The electrochemical behaviour of the electrode has been studied. The experimental results of cyclic voltammetry showed that acidic media was suitable for efficient electrochemical oxidation of 4-chlorophenoxyacetic acid. The Ti/SnO2-Sb2O5/PbO2 electrode was used as the anode and the electrolysis experiment was carried out under the optimized conditions. The electrolysis process was monitored by UV-visible spectrometry and high performance liquid chromatography (HPLC) and the chemical oxygen demand(COD) was determined by the potassium dichromate method. The mechanism of 4-chlorophenoxyacetic acid be oxided was studied primarily. The results of electrolysis experiment demonstrated the possibility that the electrode was used as an anode for electrochemical treatment of 4-chlorophenoxyacetic acid contained in the waste water.

Abstract: Environment materials (humic acid (HA), super absorbent polymers (SAP), fly ash (FM) and zeolite (FS)) were used as amendments to immobilize heavy metal Pb and Cd in artificial contaminated soils. The results showed that soil pH and EC changed after the application of single or combined and co-application amendments. The leaching Pb in the single-Pb contaminated soils amended with HA, FM, C1 (HA, SAP, FM, FS) and C2 (HA, SAP, FM) were 93%, 87%, 59% and 77% of the control without amendments, respectively. The leaching Cd in the single-Cd contaminated soils amended with SAP and C3 (HA, SAP, FS) were 64%, and 83% of the control, respectively, in four-steps leaching. The leaching Pb in the Pb-Cd co-contaminated soil amended with HA, C2 and C3 were 41%, 95% and 77% of the control, respectively. The leaching Cd in the Pb-Cd co-contaminated soil amended with HA, SAP and C3 were 85%, 72% and 55% of the control, respectively. The results indicated that C1 and SAP was the best amendments for single Pb and Cd contaminated soil, respectively. While the combined amendment, HA and C3 could prevent Pb and Cd to be leached from co-contaminated soils, respectively.

Abstract: The feature of coal-sludge slurries(CSSs) were studied by mixing Shenhua coal and sewage sludge collected from Huainan sewage treatment plant. The results showed that, the rheological properties of CSSs prepared with the adding dosage from 0 to 15% were the shearing and diluting feature. With the adding dosages of the sludge increase, the apparent viscosity values increased and the maximum solid concentrations of CSSs decreased. Also, the gasification kinetics were studied by Thermogravimetry-Fourier Transform Infrared(TG-FTIR). The gasification starting temperatures and activation energy decreased with the adding dosages of the sludge increase, it indicated that the process was accelerated by sewage sludge.

Abstract: The leaching characteristics of chemical components from converter steel slag were studied through circulating leaching experiments. Results show that the most quality of leaching is CaO, SiO₂ is the second and Al₂O₃ is the least. Analyzing the leaching process and experimental results, it can conclude that the leaching kinetics is controlled by intra-paticle diffusion. The leaching process can be described by shrinking unreacted core model.