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The intensified effect of nitrogen removal properties using Pseudomonas fulva K3 and MgBC for the weathered crust rare earth wastewater treatment

Deng Xiangyi, Chi Ruan, Xiao Chunqiao, Zhang Zhenyue, Liu Xuemei, Hu Jingang

Physicochemical Problems of Mineral Processing

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2021

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Vol. 57, iss. 3

84--96

EN

A new bacteria named Pseudomonas fulva K3 (P. fulva) strain was isolated from the surroundings of weathered crust rare earth tailing with efficient NH4+-N removal ability via heterotrophic nitrification and aerobic denitrification. The nitrogen removal properties could be intensified by the synergistic effect between as-prepared magnesium-modified biochar (MgBC) and P. fulva strain. The results show that P. fulva exhibited a rod-shaped morphology and NH4+-N can be completely biodegraded under the optimal conditions of pH=7.0~8.0, temperature 30 oC and initial NH4+-N concentration of 100 ~150 mg/L. The NH4 +-N tolerant concentration for P. fulva was determined to be 300 mg/L. The magnesium-modified biochar (MgBC) worked as an adsorbent of NH4+-N. The kinetics and isotherm model for adsorption could be described by the pseudo-secondorder kinetic and Freundlich model, respectively. The XPS results showed that NH4+-N was mainly adsorbed on the surface by chemical adsorption. Furthermore, the P. fulva could be immobilized on MgBC due to its large surface area, adjusting the concentration of NH4+-N to a proper range for the growth of P. fulva by adsorption and desorption equilibrium, and leading to the intensified effect on nitrogen removal. The total nitrogen removal efficiency of the eluted weathered crust rare earth tailing reached 84.7 % in MgBC + P. fulva system.

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Screening of high-efficiency potassium-dissolving strains and optimization of the potassium-dissolving process

Xue Yongping, Xiao Chunqiao, Zhang Yantu, Chi Ruan

Physicochemical Problems of Mineral Processing

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2021

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Vol. 57, iss. 2

1--13

EN

The biosolubilization of potassium feldspar (K-feldspar) by potassium-dissolving microorganisms has become a hot research topic. However, the screening of highly efficient potassiumdissolving strains from the soils of mining areas has not been reported. In this study, 82 strains with potassium-dissolving ability were screened from soils collected from a K-feldspar mining area in Suizhou, Hubei Province, China. One of them, JX-20, was a gram-positive is spherical bacteria with smooth edges, which was identified as a new strain by 16S rRNA gene sequencing. Simultaneously, the influences of temperature, initial pH value, inoculation volume, incubation time, shaking speed, Kfeldspar concentration, K-feldspar granularity, and the ammonium sulfate dose on the potassium releasing ability of the JX-20 strain were investigated. The results showed that the JX-20 strain had an obvious dissolution effect on K-feldspar. The optimum conditions for the JX-20 strain to remove potassium from K-feldspar were as follows: cultured at 28-30℃ for ten days, initial pH value of 7.4-8, 60 mL medium in a 250 mL conical flask, and 170 r/min shaking speed on a rotary shaker. The Kfeldspar concentration, inoculation volume, K-feldspar granularity, and ammonium sulfate dose were 2 g/L, 20%, 0.02-0.03 mm, and 0.4 g/L, respectively. Under the above conditions, the highest corrosion efficiency of 39.75% was achieved.

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Enhanced biosolubilization of mid-low grade phosphate rock by formation of microbial consortium biofilm from activated sludge

Xiao Chunqiao, Wu Xiaoyan, Zhu Lei, Yu Tong, Xu Zhenghe, Chi Ruan

Physicochemical Problems of Mineral Processing

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2019

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Vol. 55, iss. 1

217--224

EN

Mid-low grade phosphate rock (PR) is a potential source of free phosphate to facilitate crop growth, but a cost effective and environmentally responsible extraction process is required. In this study, the capacity of a microbial consortium from activated sludge to solubilize PR in a laboratory-scale column reactor was investigated. The microbial consortium proved capable of efficiently releasing soluble phosphate in the reactor effluent over the 90-day trial. The microbial consortium grew well in the column system as evidenced by reduced chemical oxygen demand (COD) in the reaction solution. Biofilm formation was identified as critical for biosolubilization of the mid-low grade PR. Imaging of the biofilm by scanning electron microscopy (SEM) revealed a dense network of microbial cells embedded in extracellular polymeric substances (EPS). The biofilm contained both oxic and anoxic zones. The pH decreased significantly in both the biofilm and the reaction solution during operation, indicating healthy growth of the microbial consortium with corresponding acid generation and subsequent enhancement of phosphate solubilization.