期刊
APPLIED CLAY SCIENCE
卷 165, 期 -, 页码 103-111出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.clay.2018.08.010
关键词
Opal-palygorskite clay; Comprehensive application; 4A zeolite; Box-Behnken design; Hg2+ removal
资金
- National Natural Science Foundation of China (NSFC) [41572028]
To availably utilize opal-palygorskite clay, dry beneficiation technique was applied to separate opal and palygorskite clay. Based on separated opal from opal-palygorskite clay, 4A zeolite was successfully synthesized by using a hydrothermal method. Box-Behnken was used to optimize Na2O/SiO2, H2O/Na2O and SiO2/Al2O3 with cation exchange capacity (CEC) as the response value. The optimum parameters was determined to be Na2O/SiO2 = 1.0, H2O/Na2O = 40, and SiO2/Al2O3 = 2.0, and CEC got the maximum of 2.99 mmol/(g.dry zeolite) under the conditions. The as-obtained 4A zeolite was characterized by using X-ray diffraction (MD), thereto gravimetric analysis (TG), acid-base titration, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and then was applied to remove Hg2+ from aqueous solution. The maximum removal capacity of Hg2+ was 41.99 mg/g and adsorption equilibrium was obtained with contact time of 2 h. Effects of pH, ionic strength, temperatures, metal cations, strippant kinds and cycle times on removal behaviors of Hg2+ onto 4A zeolite were investigated by batch experiments. The kinetics and isotherms of Hg2+ adsorption fitted well by pseudo-second kinetic and Langmuir models. When Hg2+ -adsorbed 4A zeolite was desorbed using 1 mol/L NaNO3 solution, the adsorption efficiency was maintained about 70% after four cycles.
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