Preparation of peanut shell composite hydrogel and its adsorption properties of lead and cadmium

Peanut shells lignocellulose/β-cyclodextrin/acrylic acid composite hydrogel (PS(H)/β-CD/PAA) was prepared by free radical polymerization, using peanut shells(PS) and acrylic acid(AA) as polymerization monomers, potassium persulfate(APS) as initiator, N,N-methylenebisacrylamide(MBA) as crosslinking agent, β-cyclodextrin(β-CD) as reinforcing material. The surface properties and size morphology of the composite hydrogel adsorbent were characterized. The adsorption behavior and mechanism of PS(H)/β-CD/PAA on Cd²⁺ and Pb²⁺ under different environmental factors were investigated. As a result, PS(H)/β-CD/PAA had a porous network structure and positive mechanical properties when β-CD was added. PS(H)/β-CD/PAA presented lower synthesis cost and recyclability. The adsorption of PS(H)/β-CD/PAA on Cd²⁺ and Pb²⁺ reached adsorption equilibrium within 60 min and worked effectively in a wide pH range of 3-8. The maximum adsorption capacity of PS(H)/β-CD/PAA composite hydrogel for Cd²⁺ and Pb²⁺ was 115.67 and 181.71 mg/g, respectively. The adsorption process of PS(H)/β-CD/PAA on Cd²⁺ and Pb²⁺ was mainly carried out through ion exchange, complexation or coordination interaction. In addition, when treating actual wastewater, the removal efficiency of PS(H)/β-CD/PAA on Pb, Cd²⁺, Cu²⁺ and Ni²⁺ was 76.4%, 88.6%, 72.9% and 31.6%, respectively. In a word, PS(H)/β-CD/PAA exhibited good effectiveness in treating heavy metals in water, took full advantage of resources and saved costs, and could serve as a potential new material for heavy metal wastewater treatment.