Abstract: Modified coal gasification slag (MCGS) adsorption material was prepared by hydrothermal method, by NaOH activation to remove Cd2+ from aqueous solution. Due to the low Cd2+ adsorption capacity of coal gasification slag (CGS), the modification conditions were optimized by Box-Behnken response surface method. X-ray diffraction (XRD) analysis revealed the presence of amorphous "steamed bread" SiO2 and residual carbon peaks in the range of 15°~30° in the coal gasification slag (CGS). These peaks had broad diffraction patterns. Fourier transform infrared (FTIR) spectroscopy showed that MCGS contained stretching and bending vibration peaks for the Si-O-T bond (where T is either Al or Si), indicating that the modified Si-O-Si bond had been broken and the vibration peak had increased. Scanning electron microscopy (SEM) images showed that the CGS mainly consisted of microbeads with smooth surfaces and flocculent or flaky blocks. The surface of the MCGS had an abundance of pores, with a specific surface area, pore volume, and pore diameter of 255.08 m2/g, 0.24 cm3/g, and 3.72 nm, respectively. The modification results showed that the best reaction conditions of MCGS were basicity 6.20%~8.10%, temperature 102~108℃, and time 138~192 min, and the temperature was the greatest influence on Cd2+ adsorption performance of MCGS. The adsorption results showed that when the concentration of Cd2+ was 50 mg/L and the dosage of MCGS was 0.10 g, the saturated adsorption capacity of Cd2+ was 13.96 mg/g; when the concentration of Cd2+ was 40 mg/L and the dosage of MCGS was 0.20 g, the removal rate of Cd2+ was 98.08%. The adsorption of Cd2+ on modified coal gasification slag follows a quasi second-order kinetic model, indicating that the adsorption of Cd2+ by MCGS was mainly chemical adsorption. The isothermal adsorption of Cd2+ onto the modified slag can be described well by the Langmuir model, indicating a monolayer adsorption process. This study can provide a theoretical basis for the treatment of Cd2+ wastewater with alkali-modified coal gasification slag.

Key words: coal gasification slag, modification, adsorption of heavy metals, Box-Behnken response surface method

摘要： 以固体废弃物煤气化渣(CGS)为材料，通过水热法制备改性煤气化渣(MCGS)吸附材料，并用于吸附Cd2+。由于CGS吸附Cd2+能力较低，利用Box-Behnken响应面模型方法优化改性条件，X射线衍射仪、傅里叶变换红外光谱仪等表征CGS及制备的MCGS的物理化学性质。改性结果表明，MCGS最佳反应条件为碱度6.20%~8.10%、温度102~108℃和时间138~192 min，温度对MCGS吸附Cd2+性能影响最大。改性后Si-O-Si键断裂，MCGS表面含有丰富的孔隙结构，比表面积、孔容和孔径分别为255.08 m2/g, 0.24 cm3/g和3.72 nm；吸附结果表明，当Cd2+浓度50 mg/L、MCGS投加量为0.10 g时，Cd2+饱和吸附量为13.96 mg/g；当Cd2+浓度40 mg/L、MCGS投加量为0.20 g时，Cd2+去除率98.08%；MCGS对重金属Cd2+的吸附过程符合准二级动力学模型和Langmuir模型。本研究可为CGS处理含Cd2+废水提供理论依据。

关键词: 煤气化渣, 改性, 重金属吸附, Box-Behnken响应面法