Study on the Adsorption and Separation of Lead/Zinc Ions by Using Citric Acid-modified Brewer’s Spent Grain
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Abstract:
Brewer’s spent grains (BSGs) were used as the raw material to conduct citric acid modifications. The raw and modified BSGs were characterized by Brunauer-Emmett-Teller (BET) surface area analysis and Fourier transform infrared spectroscopy (FTIR), and the changes in the performance of dynamic adsorption of single component Pb2+ and Zn2+ before and after the BSG modification were studied. Additionally, various factors of the fixed bed on the adsorption and separation of heavy metal ions Pb2+ and Zn2+ were investigated, providing a novel approach for the practical application of BSGs in the separation of Pb2+ and Zn2+ in wastewater. The test results showed that the mesopore/micropore ratio and specific surface area of citric acid-modified BSGs increased to some extent, and the number of carboxyl groups increased, demonstrating that citric acid modification was generally successful. In the Pb2+ and Zn2+ adsorption and separation system, the pH of wastewater and the height of the adsorption column had a relatively large impact on the selective adsorption and separation of Pb2+ and Zn2+ using modified BSGs, while the initial concentration ratio of the two components had a relatively small impact. The results showed that the modified BSG fixed bed could effectively separate lead and zinc ions in wastewater when the lead and zinc ion concentrations were 30 mg/L and 15 mg/L, respectively, pH was 4.5, flow rate was 6 mL/min, and the height of the adsorption column was 12 cm. After adsorption, the concentration of Pb2+ in the effluent was less than the 0.5 mg/L that is required by the national standard (GB), and the operation time for adsorption and separation was 8.67 h.
