Hui Yang,Baozhong Ma,Shuyang Shi,Jiancheng Yu,Yubo Liu,Zhihe Cao,Chengyan Wang
The alkali method has been proven to be an effective approach for lithium (Li) and rubidium (Rb) extraction; however, the significant dissolution of silicon (Si) remains a challenging issue. A high Si concentration in the leachate can cause filtration difficulties and pipeline blockages, while also negatively affecting phase separation during the subsequent extraction of Rb. Additionally, since the leachate needs to be recycled, the removal of Si from the leach liquor is essential. This study introduces an innovative approach of adding Al(OH) 3 for Si removal during the alkali leaching of lithium concentrate. Preliminary single-factor experiments demonstrate that Al(OH) 3 effectively reduces the Si concentration in leach liquor but also consumes NaOH, leading to a decline in Li and Rb leaching efficiency. Given the interaction between Al(OH) 3 addition and NaOH concentration on element leaching, Response Surface Methodology was employed to predict and optimize the parameters of the leaching process. Under the optimal parameters of 290 g/L NaOH concentration, 39 % Al(OH) 3 addition, and 120 °C leaching temperature, the experimental leaching efficiencies of Li, Rb, and Si were 99.8 %, 87.9 %, and 4.1 %, respectively. Subsequently, Rb was separated with Li via solvent extraction under high alkaline conditions. The single-stage extraction efficiency of Rb was 82.8 % at optimized conditions, and after four-stage countercurrent extraction, the overall Rb recovery could reach 99.2 %. The innovative alkali method proposed not only enables the synergistic extraction and separation of Li and Rb but also achieves effective Si removal and its utilization.
This study investigated how different extraction parts of raw materials and different flocculation methods affect the extraction yield, structure, and properties of sodium alginate. The aim was to improve the quality of sodium alginate and provide theoretical guidance for upstream enterprises. In this study,Lessonia nigrescens(LN) was used as a raw material. The alkali treatment conditions were optimized. The optimal extraction conditions were determined to be a 2% sodium carbonate concentration, a duration of 4 h, a material-to-liquid ratio of 1:40, and a temperature of 60 °C, achieving an extraction yield of 43.03%. LN was categorized into blades, stipes, holdfasts, and whole seaweed for comparative analysis, and sodium alginate was flocculated using the acid, calcium, and ethanol methods. Structural and physicochemical analyses showed that the mannuronic acid/guluronic acid (M/G) ratios of the twelve sodium alginate samples ranged from 5.73 to 8.76. The LN part had a greater influence on the M/G ratio than the flocculation method. The relative molecular weight (2343–3074 kDa) and viscosity (170–331 mPa·s) exhibited consistent trends. For the same part, the effect of the flocculation method on the molecular weight followed the order ethanol > acid > calcium. The physicochemical properties of the extracted sodium alginate met the requirements specified in the physicochemical index standard GB 1886.243-2016 of China.
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