42 / 2021-06-29 11:41:48

Removal characteristics of Pb(II) and Cd(II) from aqueous single metal solutions by vermicompost combined with nano-CaO

Vermicompost; Adsorption; Heavy metal; Nanomaterials

Vermicompost (CV) and nanomaterials have been identified as potentialamendments to adsorb environmentally toxic heavy metals. This study analyze multi-aspect properties of CV and its nanocomposite (CV-nCa) with nano CaO (nCaO) as pH, electrical conductivity(EC), cation exchange capacity (CEC), ash content and surface characteristics, aiming to compare their potential for removing aqueous Pb(II) and Cd(II). The results demonstrated that CV-nCa had a higher pH, EC, CEC, ash content, pore parameters and specific surface area than CV. Adsorption isotherm studies showed that CV-nCa had a high adsorption capacities for Pb(II) andCd(II), with the maximum adsorption capacities (Langmuir model) being 255.1and 137.7 mg∙g^-1. the adsorption rates (ARs) by CV-nCawere both above 99.72%within the initial concentration ofPb(II ) being 200-800 mg∙L^-1 Cd(II) being100-200 mg∙L^-1. Besides, CV-nCa could effectively remove Pb(II) and Cd(II) within a widerpH range (3-6) and a lower MC of 4 g∙L^-1. Kinetic studies showed that the Pb(II) and Cd(II) adsorption by CV were best fitted with the Elovich and pseudo-first-order model, while for CV-nCa were both best fitted with the pseudo-second-order model. FTIR analysis demonstrated that the interaction of CV and CV-nCa with Pb(II) and Cd(II) mainly depended on thearomatic/aliphatic acids,some primary/secondary alcohols and some silicate and carbonates. XRD analysis showed that the addition of nCaO into CV mainly increased CaCO₃ content and affected the adsorption characteristics. Thus, combining nanometallic CaO with vermicompost may broadenheavy metal remediation and vermicompost utilization in the environment.