Ternary‐grafted starch‐based hydrogel with improved adsorption capacity for dyes

Biomass‐based hydrogels can be used as the adsorbents in sewage water, as they have good adsorption capacity for heavy ions and dyes. A ternary‐grafted starch‐based hydrogel, St 1.0 /CMC 0.5 /P(AM 3.0 ‐AA 5.0 ‐AMPS 1.0 ), was prepared using cornstarch (St) and sodium carboxymethyl cellulose (CMC) as raw materials, with acrylamide (AM), acrylic acid (AA), and 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) as graft monomers. Due to the introduction of CMC and AMPS, the number and type of effective adsorption functional groups in the St 1.0 /CMC 0.5 /P(AM 3.0 ‐AA 5.0 ‐AMPS 1.0 ) hydrogel increased, leading to an improved adsorption capacity and removal rate for methylene blue (MB). The maximum adsorption capacity and removal rate for MB could be 1624.49 mg/g and 91.8 %, respectively, at 25 °C. According to the adsorption isotherm and adsorption kinetics, the MB adsorption process on the hydrogel occurs according to the Langmuir isotherm model and quasi‐second‐order kinetics via a chemisorption process occurring on the adsorbent monolayer. Moreover, the St 1.0 /CMC 0.5 /P(AM 3.0 ‐AA 5.0 ‐AMPS 1.0 ) hydrogel displayed good regeneration performance. The removal rate for MB could still achieve 84.3 % after the hydrogel was reused four times.