Investigation of the influence of crosslinking activation methods on the physicochemical and Cu(II) adsorption characteristics of cellulose hydrogels

Abstract

Hydrogels represent an attractive soft material with promising applications in many fields. Conventional methods for hydrogel preparation typically involve heat curing either by water-bath (WB) heating or microwave (MW) irradiation to facilitate crosslinking. However, a detailed investigation of the influence of WB- and MW-mediated crosslinking process on the characteristics of hydrogels has been rarely reported. This work aims to evaluate the physicochemical properties of epichlorohydrin (ECH) crosslinked cellulose hydrogels prepared by WB and MW heating methods, including pore morphology, chemical composition, crystallinity, thermal stability, and water absorption capacity. The results showed that MW heating could accelerate the crosslinking reaction between cellulose and ECH to produce robust hydrogel, with a 3 min total irradiation time at 400 W compared to 2 h at 60 °C under conventional WB heating. The total utility cost to produce WBH is US$ 0.052, which is 14 times higher than MWH (US$ 0.004). The estimation of the total production cost of MWH on a large scale is US$ 2.86 per kg. Moreover, the as-prepared MWH displayed outstanding performance in Cu(II) removal at 30 °C and pH 7, with a maximum adsorption capacity of 119 mg/g, respectively. The kinetic and equilibrium behaviors of Cu(II) ions on WBH and MWH were best described by pseudo-second order and Langmuir isotherm models, respectively.