Optimization of synthesis condition for carboxymethyl cellulose‐based hydrogel from rice straw by microwave‐assisted method and its application in heavy metal ions removal

BACKGROUND An alternative carboxymethyl cellulose‐based biosorbent hydrogel was synthesized by grafting 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) onto the prepared carboxymethyl cellulose backbone via microwave heating. Response surface methodology was employed to optimize the hydrogel synthesis condition for maximum gel content with respect to AMPS dose, N,N′‐methylene‐bis‐acrylamide dose, and microwave exposure time. The prepared gels were then characterized and evaluated in terms of their heavy metal ions adsorption performance and reusability. RESULTS The optimum synthesis condition yielded the maximum gel content and maximum equilibrium swelling of 96.33% and 2819 ± 15%, respectively. The Langmuir model fitted the experimental isotherm data well, with maximum adsorption capacity of 86.21, 102.04 and 33.56 mg g‐1 for Cu2+, Pb2+ and Fe3+, respectively. Microwave heating was clearly noted to result in hydrogel of higher porosity and could shorten the synthesis time by 88.33%; the gel content was 7.46% higher compared with that obtained via conventional heating. CONCLUSION Microwave‐assisted heating is a feasible alternative and an efficient technique for CMC‐g‐AMPS hydrogel synthesis. The optimized CMC‐g‐AMPS hydrogel exhibited good performance for Cu2+, Pb2+ and Fe3+ ions removal and was satisfactorily reused, thus contributing to the alleviation of environmental problems caused by discarded rice straw and water contaminated with heavy metal ions.