Adsorption of Cu2+ and Pb2+ from Municipal Wastewater by Intercalation Polymerization Modified Kaolin

Abstract

Adsorption method has attracted extensive attention in heavy metal wastewater treatment due to its low cost, abundant sources, and simple operation. Kaolin is utilized as raw material, waterborne polyurethane is utilized as dispersion medium, and dimethyl sulfoxide (DMSO) is utilized as intercalation agent, to prepare intercalation polymerization modified kaolin material (KBEP). It is then characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetry (TG), and other methods. The polymer is utilized for static adsorption of Cu2+ and Pb2+, and the kinetic analysis of the adsorption process is carried out. The results show that the layer spacing of kaolin increases substantially (from 0.69 nm to 0.81 nm) after modification. When the content of kaolin is less than 1.7%, kaolin exists in intercalation or stripping state in waterborne polyurethane matrix. When the content of kaolin is higher than 1.7%, kaolin can exist in the form of agglomeration with waterborne polyurethane matrix. Compared with pure polyurethane, the composite’s thermal stability is improved, and the maximum thermal weight loss of the hard section is increased by 50 °C. When kaolin content is 2.5%, the temperature of the hardness and the fastest thermal decomposition rate of the soft section increases by 30 °C and 26 °C, respectively. The adsorption test reveals that the Cu2+ elimination rate reaches 93.7% when the addition amount of the prepared material reaches 1.5 g/L. When the addition amount of the prepared material reaches 0.6 g/L, the Pb2+ elimination rate reaches 95.8%. With the increase of the dosage of kaolin composite, the adsorbability of the polymer to the two metal ions decreases gradually. Kinetic experiments show that the adsorption of Cu2+ and Pb2+ is in line with the pseudo-second-order kinetic (PSOK) equation. The adsorbability of Cu2+ and Pb2+ is 75.3 mg/g and 268.6 mg/g, respectively. The adsorption way is mainly chemical adsorption.