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3 Physicochemical Problems of Mineral Processing

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Adsorption behaviors of As(III) on bentonite, diatomite, and hematite : implications for scientific remediation of arsenite contamination in soil

100%

Fu K. , Tang P. , Zhang W. , Chen S. , Tao G. , Liu J.

Physicochemical Problems of Mineral Processing

2024

tom Vol. 60, iss. 4

art. no. 192381

Comprehensive understanding of As(III) sorption on natural minerals in contaminated soils is important for scientific decision making in remediation. In this study, the characteristics of As(III) adsorption on three minerals with different crystal structures and chemical compositions (bentonite; diatomite; and hematite) were investigated. The adsorption kinetics and thermodynamics were established. Surface complexation modeling was performed using X-ray diffraction spectroscopy, fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results showed that the pH value had a more significant effect on As(III) adsorption on hematite than on bentonite and diatomite, and As(III) was efficiently adsorbed by hematite at pH 7.0. The pseudo-first-order model provided an excellent fit to the As(III) adsorption on bentonite and hematite; the diffusion of ions or groups played an important role in the adsorption of As(III) on bentonite and hematite. The adsorption of As(III) on diatomite could be fitted with pseudo-first-order and pseudo-second order kinetic equations, as their regression coefficients were equal (R2=0.999). It was inferred that the adsorption of As(III) on diatomite occurred through solution diffusion and surface chemisorption. The As(III) adsorption on bentonite and diatomite was mainly physical and multilayer adsorption, whereas the As(III) adsorption on hematite was mainly chemical and monolayer absorption. The As(III) adsorption on hematite was divided into two stages: fast and slow. At first, the inner monodentate complex (such as ☰Fe-OAs3H-) formed at a high rate, and with the increase in the coverage of As(III) on the surface of iron oxide, the monodentate complex was slowly converted to the bidentate complex. These results verify the possibility of using bentonite, diatomite, and hematite as alternative materials for the remediation of As(III)-contaminated soils, and also indicate that bentonite and diatomite are suitable for the remediation of low As(III)-contaminated soils, while hematite is suitable for the decontamination of high As(III) polluted soil. Selecting suitable remediation materials according to arsenic contamination level is the key to soil scientific remediation.

A novel method for purification of phosphogypsum

100%

Wang J. , Dong F. , Wang Z. , Yang F. , Du M. , Fu K. , Wang Z.

Physicochemical Problems of Mineral Processing

2020

tom Vol. 56, iss. 5

975--983

Phosphogypsum is an industrial solid waste from the phosphate fertilizer industry. At present, the accumulation of phosphogypsum has caused very serious economic and environmental problems. A large scale of phosphogypsum is consunmed in the building field. The characteristics of whiteness and phosphorus content are important factors affecting the use of phosphogypsum as a building material. In this study, soluble phosphorus and fluorine were removed by adding lime, and flotation was employed to purify phosphogypsum. A large amount of organic matter and fine slime in the phosphogypsum were removed by reverse flotation, and gypsum was floated by positive flotation. Through the flotation closed-circuit experiment, the whiteness of phosphogypsum was increased from 31.5 to 58.4, the percentage of total phosphorus in gypsum (P2O5) was reduced from 1.78 to 0.89, the grade of calcium sulphate dihydrate was 96.6%, the recovery of concentrate was 74.1%. After removing impurities, the phosphogypsum concentrate reached the first grade national standard of the phosphogypsum building materials in China. The method is cheap and practical, and can be used as an important method for pretreatment of phosphogypsum.

Stirred-tank leaching of coarse-grained waste, printed circuit boards with Acidithiobacillus ferrooxidans

100%

Fu K. , Tian L. , Hou P. , Long M. , Chen S. , Lin H.

Physicochemical Problems of Mineral Processing

2021

tom Vol. 57, iss. 5

153--163

Stirred tank leaching of metals from coarse-grained waste, printed circuit boards (WPCB) used Acidithiobacillus ferrooxidans (A. ferrooxidans) at ambient temperature (20-35°C). The effect of the baffle size, WPCB concentration, and inoculation volume was tested. 95.92% of Cu, 93.53% of Al, 92.58% of Zn, 65.27% of Ni, and 95.33% of Sn in WPCBs were leached under the optimal conditions: no baffle, WPCB concentration of 5.0% (w/w), and inoculation volume of 5% (v/v). The alkaline substance and reactivity metal of WPCBs, and the oxidation of Fe2+, consume H+. Adding acid can maintain the pH value of the leaching solution, which is conducive to the growth and reproduction of the bacteria and improves the leaching efficiency of WPCBs. The second-order dynamics model can describe the acid consumption in the bioleaching process of coarse-grained WPCBs. Moreover, the Avrami equation can successfully explain the bioleaching kinetics of Cu, Al, Zn, Ni, and Sn from the coarse-grained WPCBs. The key factors controlling the bioleaching of coarse-grained WPCBs are metal reactivity and specific surface area. These results revealed that bioleaching metals from coarse-grained WPCBs using A.ferrooxidans is feasible, and has important significance to guiding its industrialization.