Ying Zhao

Removal of phosphate from aqueous solution by red mud using a factorial design.

The purpose of the work is to study the adsorption of phosphate on red mud from aqueous solutions using 2(3) full factorial designs. The important parameters, which affect the removal efficiency of phosphate and final pH of solution (pH(f)), such as phosphate concentration, initial pH of solution (pH(i)) and the red mud dosage were investigated. The effects of individual variables and their interaction effects for dependent variables, namely, phosphate removal efficiency and pH(f) were determined. The results of the study showed that phosphate removal efficiency and pH(f) were found to be 97.6% and 10.9 with optimal reaction conditions initial phosphate concentration 25 mg l(-1), red mud dosage 1.5 g l(-1), pH(i) 3.0, respectively. It was found that adequate amount of calcium ions and higher final pH than 9 are ideal conditions for maximum phosphate removal.

Removal of tetracycline from aqueous solution by MCM-41-zeolite A loaded nano zero valent iron: Synthesis, characteristic, adsorption performance and mechanism

In this study, nano zero valent iron (NZVI) modified MCM-41-zeolite A (Fe-MCM-41-A) composite as a novel adsorbent was prepared by precipitation method and applied for tetracycline (TC) removal from aqueous solution. The adsorbent was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and N2-BET analysis. Hysteresis loops indicated that the sample has a desirable magnetic property and can be separated quickly. Adsorption studies were carried out to evaluate its potential for TC removal. Results showed that the optimal Fe-MCM-41-A dosage, initial pH and reaction time at initial TC concentration of 100mgL-1 solution are 1gL-1, pH=5, and 60u2009min respectively, at which the removal efficiency of TC was 98.7%. The TC adsorption results fitted the Langmuir isotherm model very well and the adsorption process could be described by a pseudo-second-order kinetic model. A maximum TC adsorption capacity of 526.32mgg-1 was achieved. This study demonstrates that Fe-MCM-41-A is a promising and efficient material for TC adsorption from aqueous solution.

Decolorization of Methyl Orange by a new clay-supported nanoscale zero-valent iron: Synergetic effect, efficiency optimization and mechanism

In this study, a novel nanoscale zero-valent iron (nZVI) composite material was successfully synthesized using a low-cost natural clay, Hangjin 2# clay (HJ clay) as the support and tested for the decolorization of the azo dye Methyl Orange (MO) in aqueous solution by nZVI particles. According to the characterization and MO decolorization experiments, the sample with 5:1 HJ clay-supported nZVI (HJ/nZVI) mass ratio (HJ-nZVI5) showed the best dispersion and reactivity and the highest MO decolorization efficiency. With the same equivalent Fe0 dosage, the HJ-nZVI1 and HJ-nZVI5 samples demonstrated a synergetic effect for the decolorization of MO: their decolorization efficiencies were much higher than that achieved by physical mixing of HJ clay and nZVIs, or the sum of HJ clay and nZVIs alone. The synergetic effect was primarily due to the improved dispersion and more effective utilization of the nZVI particles on/in the composite materials. Higher decolorization efficiency of MO was obtained at larger HJ-nZVI dosage, higher temperature and under N2 atmosphere, while the MO initial concentration and pH were negatively correlated to the efficiency. HJ clay not only works as a carrier for nZVI nanoparticles, but also contributes to the decolorization through an adsorption-enhanced reduction mechanism. The high efficiency of HJ-nZVI for decontamination gives it great potential for use in a variety of remediation applications.

Review of challenges and strategies for balanced urban-rural environmental protection in China

With the rise of environmentalism in China, great efforts have been devoted to environmental protection over the past several decades. Compared with urban environmental protection, rural environmental protection has not been attached enough importance in China due to the dual-track structure of socio-economic development. As a result, rural China is shouldering disproportionally heavy environmental burdens partly because of the differences and biases between urban and rural environmental protection seen in environmental policies, environmental rights and interests, environmental protection investment, and the environmental protection awareness of people. To eliminate the gap between rural and urban environmental protection, and achieve the goal of “balanced urban-rural environmental protection” (BUREP), government should consider mapping out proper policies and strategies. In this paper we put forward an innovative strategy of BUREP against the background of China’s urban-rural environmental protection. First, we review the current status of rural environmental protection status and its challenges compared with urban environmental protection in China. Secondly, we analyzed the main driving factors and reasons deeply, and then we put forward the BUREP strategy base on the unequal status between urban and rural environment. Finally, we proposed the framework of BUREP. This study may serve as a scientific reference regarding decision-making in coordinating urban and rural environmental protection and in constructing the new countryside of China.

Removal of ammonium ions from aqueous solutions using zeolite synthesized from red mud

AbstractThis study investigates the removal of ammonium from aqueous using zeolite synthesized from red mud. The zeolite was characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), the specific surface area, and the cation exchange capacity (CEC). SEM and XRD indicated that most of the synthetic zeolite was crystalline, with zeolite P and Analcime as the major components. The CEC increased from 81.9 to 111xa0mmol/100xa0g during the synthesis process. The effects of adsorbent dosage, shaking time, initial pH, initial ammonium ion concentration, and competitive cations were investigated by batch experiments. The result shows that the parameters mentioned above have great influence on the ammonium removal by using the synthesized zeolite, and the effect of cations follows the order Na+u2009>u2009K+u2009>u2009Ca2+u2009>u2009Mg2+. To understand the exchange process of ammonium by the synthesized zeolite, the adsorption dynamics was described by Ho’s pseudo-second-order kinetic model. The Ho’s pseudo-second-order k...

Preparation of coagulant from red mud and semi-product of polyaluminum chloride for removal of phosphate from water

Abstract Traditionally, calcium aluminate, caustic soda, lime or aluminum slag was employed as alkali for basicity adjustment in the production of polyaluminum chloride (PACl). In this work, red mud (RM), a highly alkaline waste from alumina industry, was utilized instead of the traditional alkali. A composite coagulant (RMPACl) was prepared from RM and the semi-product of polyaluminum chloride (ACl). Important factors for preparation, such as RM/ACl ratio, reaction temperature and reaction time, were investigated and optimized to be as follows: RM/ACl ratio of 0.25 (w v−1), reaction temperature of 80°C and reaction time of 4 h. The results of coagulation tests showed that RMPACl exhibited better performance than PACl for removal of phosphate. The optimum coagulation pH range of RMPACl was found to be 6.0–8.5. High phosphate removal efficiency (>94.9%) was achieved by dosing RMPACl at the dosage of 147.5 mg l−1. Therefore, RMPACl was considered as a low-cost coagulant, which possessed a good coagulation p...

The metal ions release and microstructure of coal gangue corroded by acid-based chemical solution

Cationic release, surface microstructure, and pore size distribution of coal gangue during the acid-based chemical solution corrosion were investigated. Results showed that during the interactions of gangue and chemical solution, the acidity and alkalinity of mixed solutions first decrease quickly, and then stabilize. The concentrations of released Ca, Mg, and Fe in gangue decrease with the decreasing acidity of the chemical solution, and produce a trend of increase-to-decrease with the increase in alkalinity. The release of Ca, Mg, and Fe is significantly influenced by the weathering of gangue. Ca and Mg achieve a concentrated release during the first day, whereas the release of Fe occurs gradually within the first 10xa0days. The microstructure detection result indicates that the surface structure of fresh gangue is exposed to obvious corrosion by acid-based chemical solutions, with higher extent of corrosion in acidic solution than that in alkaline solution. The micropore is relatively developed, and the secondary and middle pores increase gradually. The specific surface area is increased. Furthermore, the pore size distribution of abundance of micropore and middle pore shows a series of inconsistent spectra instead of a continuous wide-flat spectrum.

Reduction of phosphorus release from high phosphorus soil by red mud

The high phosphorus levels cause the release of phosphorus from soils, thereby increasing the potential for phosphorus export to adjacent water bodies. The loss of phosphorus from soils to surface waters is a major source of water quality impairment. Therefore, soil phosphorus immobilization seems necessary. In this study, red mud (RM) was employed to immobilize phosphorus in a typical agricultural soil. It was found that phosphorus was effectively immobilized by RM. Batch leaching experiments showed that RM reduced phosphorus release from 14.38 to 2.56xa0mg/kg when soil was amended with 1% RM. Column leaching experiments showed that RM reduced the total amount of phosphorus released from 36.73 to 18.79xa0mg/kg during the investigated period. Sequential chemical extraction results indicated that RM amendment transformed H2O-P into more stable fractions. The results suggested that application of RM amendment to soils could significantly immobilize soluble phosphorus, reducing phosphorus release to the environment.

Experimental study on the microstructure and mechanical behaviors of leachate-polluted compacted clay

The intent of this article is to investigate the microstructure characteristics and macroscopic mechanical behaviors of leachate-polluted compacted clays. X-ray diffraction, scanning electron microscope, and mercury intrusion porosimetry were used to observe the mineral component, microstructure of the compacted clays polluted by different concentrations of landfill leachate. One-dimensional swelling test, direct shear test, and permeability test were conducted to measure and analyze the swelling properties, shear strength, and permeability of leachate-polluted compacted clays. Results indicated that the leachate pollution caused a decrease in smectite content of compacted clays. Aggregate structure was destroyed by leachate pollution, causing an increase in the relative porosity of the smaller pores and a decrease in that of the larger pores. However, the total porosity increased with the leachate concentration because of the decrease in swelling deformation of compacted clay. Leachate pollution caused a significant increase in cohesion and a slight increase in internal friction angle of the compacted clays. Moreover, the permeability of the leachate-polluted compacted clays decreased with the increase in time and leachate concentration.

Efficiency of a hybrid granular bed-contact oxidation biofilm baffled reactor for treating molasses wastewater

AbstractA hybrid granular bed-contact oxidation biofilm baffled reactor (GBCOBBR) was studied with molasses wastewater for combined carbon and nitrogen removal. The GBCOBBR was operated at various organic loading rates ranged from 1.5 to 7xa0kg chemical oxygen demand (COD) m−3d−1 and ammonia nitrogen loading rates ranged from 0.05 to 0.204xa0kg xa0m−3d−1. Carbonaceous matter and nitrogen were removed simultaneously in the GBCOBBR at different recycle to influent ratios ranged from 1.5 to 2.5. The results demonstrated that when the loading rates of COD and ammonia were 3xa0kg COD m−3d−1 and 0.085xa0kg xa0m−3d−1, COD removal efficiencies of 90.2–91.5% were observed in the anaerobic unit, and over 92% by the two-stage treatment configuration (anaerobic and aerobic units) at all recycle to influent ratios. At all the recycle to influent ratios studied, almost all ammonia was converted to nitrate nitrogen with only small traces of nitrite nitrogen in the nitrification unit and total nitrogen removal efficiencies of 80.5–8...