Synthesis of a micro-nano FeOx/MnOx modified large volume non-enamel ceramsites for selective and efficient adsorption of cadmium

Abstract

The synthesis of large volume ceramsites with clay minerals for Cd(II) removal has received extensive attention. Here, micro-nano iron oxides (FeOx) and manganese oxides (MnOx) modified non-enamel ceramsites (NCs) were applied for the selective adsorption of Cd(II) from wastewater. The response surface regression model was exploited to fit the adsorption data, and the results manifested that kaolin/palygorskite (KP):microporous-forming material (MM):bonding material (BM) = 100.0:8.3:12.8 at 555 ℃ obtained the optimal adsorption ability. Furthermore, the Cd(II) adsorption was better accordance with Freundlich and pseudo-second order kinetics models, and FeOx/MnOx-NCs and MnOx-NCs showed maximum adsorption capacity of 6.92 mg/g and 10.36 mg/g at pH 6.0, were 4.7 and 7.4 times higher than that of NCs, respectively. The analyses of Zeta potential, XRD and XPS pointed out that electrostatic attraction, surface chemical complexation with oxygen-containing functional groups and chemical precipitation were the dominant adsorption mechanisms. The FeOx/MnOx-NCs and MnOx-NCs retained their excellent removal rates (96.31% and 97.78%, respectively) for Cd(II) in the coexistence of salt cations. Moreover, high regeneration ability for both adsorbents were observed for five consecutive adsorption-desorption cycles. Therefore, this work provides new insight for producing large volume ceramsites using environment-friendly clay, which can overcome the constraints of selective adsorption of heavy metals and convert available ceramsites into a recyclable resource.