Adsorption of Cu2+ by Crosslinked Graft Copolymers of Starch

keywords:humic acid  starch  acrylic acid  adsorption materials  Cu²⁺

Abstract:With the use of acrylic acid (AA) as a monomer, humic acid (HA) and starch as raw materials, potassium persulfate (KPS) as initiator, and N,N-dimethylacrylamide (MBA) as a cross-linking agent, AA/HA/Starch graft copolymer was prepared and characterized by SEM and FT-IR. The effects of temperature, adsorption time, adsorbent dosage, pH value and Cu²⁺ initial concentration of the solution on the adsorption performance of the crosslinked graft copolymer were also investigated. The results showed that the Cu²⁺ adsorption capacity of the AA/HA/Starch graft copolymer increased firstly and then decreased with increasing adsorbent dosage and the initial pH value of Cu²⁺ solution. With the increase of Cu²⁺ initial concentration and the extension of adsorption time, the adsorption amount of Cu²⁺ increased rapidly and then stabilized. And it decreased slightly with the increase of temperature. At pH value of 5.5, temperature of 298 K, adsorbent dosage of 50 mg, adsorption time of 125 min, and 100 mL Cu²⁺ solution with Cu²⁺ initial concentration of 100 mg/L, the Cu²⁺ adsorption capacity of the crosslinked graft copolymer was 238 mg/g. The adsorption of Cu²⁺ by the adsorbent followed the pseudo-second-order kinetic equation and Langmuir isothermal adsorption model, and the adsorption was attached to monolayer chemical adsorption. This study proved that AA/HA/Starch graft copolymer could be used as an efficient adsorbent for the removal of harmful and toxic metal cations such as Cu²⁺ from industrial wastewater.