Research On Sustainable Stabilization Of Heavy Metals In Zeolite And Biochar Modified Sediment

Increasingly attention is paid to remediation of heavy metals pollution in sediments for the fact that heavy metals aggregate in sediment sink through multiple ways and possess a potential toxicity to human health for they may enter the food chain.Thus,it is in urgency to reduce harmful effects from heavy metals by adopting measures to maintain them in insoluble or inert conditions.In this research,NaCl-modified zeolite and biochar were compared for the adsorption ability of Cu²⁺,Cd²⁺and Pb²⁺in aqueous solution and the stabilizing effect on the metals in sediment-soil mixture.A column experiment was employed to investigate the leaching behavior of these metals under situation of simulated acid rain.Characteristic results indicated that NaCl-modified zeolite had properties more conducive to metal adsorption than biochar,including a higher BET surface area,bigger cation exchange capacities（CEC）and more negative surface charges.NaCl-modified zeolite had bigger adsorption capacities toward three heavy metals and present better regular change in the simple aqueous solution while biochar only adsorbed selectively towards Pb either in single or mixed solution.Adsorption capacities of NaCl-modified zeolite fitted by Langmuir isotherm model were 24.83,35.57 and 133.16 mg g^-1for Cu²⁺,Cd²⁺and Pb²⁺,respectively.Leaching results demonstrated that metal concentrations in the leachates of soil receiving zeolite-or biochar-modified sediment reduced significantly and lasted for shorter time after 100 days compared with that of soil receiving bare sediment.Moreover,the NaCl-modified zeolite presented a better performance in stabilizing the three metals than biochar.Therefore,stabilization of the dredged contaminated sediment by modified zeolite ensures an environmental-friendly reuse of the sediment in land,and makes sediment treatment easy and realizable.