Tao Pu,Yanping Li,Xiujuan Yang,Ran Ao,Quxiu Dai,Jie Yang,Zhiying Guo,Liping Ma,Zhanghong Wang
Silicoaluminophosphate-20 (SAPO-20) molecular sieve was synthesized from solid waste coal gangue (CG) and aluminum ash (Al-ash), and its adsorption capacity for CO 2 was evaluated. The content of Si and Al in raw materials was increased by hydrochloric acid pretreatment, and the synthesis conditions (NaOH/CG ratio, calcination temperature, hydrothermal reaction temperature and time, liquid–solid ratio) were optimized by single factor analysis. The synthesized products were characterized by XRD, SEM, BET, FTIR and TEM. The results showed that the SAPO-20 crystal form prepared under the optimal conditions had high purity, BET surface area of 175 m 2 /g, and pore structure with multistage pore distribution, which was conducive to gas diffusion and adsorption. Thermogravimetric analysis revealed that under the conditions of 25 °C and 1 bar, compared with the CO 2 adsorption capacity of 5.63 mg/g for CG, the CO 2 adsorption capacity of SAPO-20 was 27.92 mg/g. The adsorption process was in line with the Langmuir monolayer model and had exothermic characteristics (ΔH = –152 kJ/mol). The adsorption kinetics was fitted by Pseudo-First-Order Kinetic Model (R 2 = 0.740–0.995), and the adsorption rate increased with the increase of temperature. In addition, compared with the traditional synthesis method, the synthesis cost of this study was reduced by more than 70 %, and the carbon emission was reduced by about 75 %, realizing economic and environmental viability.
Cation and oxyanion heavy metals possess opposite physical and chemical properties, which could be hard to simultaneous remediate in soil. In this study, layered double hydroxides from secondary aluminum ash (SAA-LDH) has been synthesized for soil remediation contaminated with heavy metals. The as-obtained SAA-LDH exhibit strong affinity for heavy metals, which could remove 193.50 mg‧g −1 of Cr(Ⅵ) and 175.84 mg‧g −1 of Cd(Ⅱ) within 2 h. Optimum acid-base resistance and selectivity guarantee the practice potential of SAA-LDH, which could remove above 85 % of Cd(Ⅱ) and Cr(Ⅵ) under widely pH range (from 4.00 to 10.00), capturing above 90 % of Cd(Ⅱ) and Cr(Ⅵ) under the interference of seven coexisting ions. Soil remediation tests and column leaching experiments further demonstrate that SAA-LDH could immobilize 98.32 % of Cd(Ⅱ) and 97.71 % of Cr(Ⅵ), preventing its migration. Density functional theory (DFT) manifests that SAA-LDH could remove Cd(Ⅱ) and Cr(Ⅵ) through isomorphic substitution and ion exchange respectively under single system. Under compound system, Cd(Ⅱ) fixed with isomorphic substitution could promote the immobilization of Cr(Ⅵ) onto SAA-LDH, constructing hyper-stable coordination structure. This study provides an effective approach to simultaneously recycle hazardous waste and remediate heavy metals contamination in soil.
危险品化学品经营许可证（带存储）