Utilization of dredged river sediments to synthesize zeolite for Cd(II) removal from wastewater

[摘要] Resource utilization of dredged sediments has been an urgent issue in recent years in China. To solve this problem, an approach of zeolite synthesized by dredged sediment was proposed for the first time in this study. Then the optimum conditions for sediment-based zeolite (SZ) synthesis and its adsorption performance of aqueous Cd (II) were investigated. The results showed that the optimal parameters of SZ synthesis were 3-6 mol/L HCl as the extracting agent, a NaOH/RM ratio of 1.4:1-2.1:1, and 80-100 degrees C and 12-24 h as the crystallization temperature and reaction time. The specific surface area of the SZ (516.36 m(2)/g) was much larger than that of the initial sediment (9.51 m(2)/g), while the adsorption equilibrium of Cd (II) by SZ could be achieved within 120 min. Moreover, the maximum adsorption capacity was 206.64 mg/g at the optimal condition of pH = 5.0 and a SZ concentration of 1.5 g/L. In addition, ion exchange between Cd(II) and Na+ was demonstrated to be the predominant mechanism for Cd(II) adsorption by SZ. Other functional groups including -OH or -CH on the surface of the SZ could combine with Cd(II) to form complexes to remove Cd(II) as well. Furthermore, the SZ was successfully regenerated in this work. The findings confirmed that SZ could be reused as an effective adsorbent for the treatment of Cd(II)-polluted wastewater, which could provide a new and feasible approach to the resource utilization of dredged sediments.

[发布日期] 2021-10-20

[关键词] River sediments;Resource utilization;Zeolite;Adsorption;Cadmium-polluted wastewater