N-methyl-D-glucamine based cryogels as reusable sponges to enhance heavy metals removal from water

The design of novel cryogels containing N-methyl-D-glucamine (NMG) group was herein reported. The macroporous materials were prepared via sustainable and feasible cryopolymerization by using as co-monomers (4-vinyl-benzyl)-N-methyl-D-glucamine (VbNMG) and 2-hydroxyethyl methacrylate (HEMA) at different percentages. Particularly, cryogel containing 100% of VbNMG (VbNMG-100) showed excellent ability in fast water uptake, removing arsenic (V) and chromium (VI) metal ions from it. Reusability up to six cycles was also demonstrated. The as-prepared materials were characterized by spectroscopic, thermal, and morphological analyses. The effect of initial oxyanions concentration, kinetic profiles, interfering anions (phosphate and sulphate) were investigated and adsorption/desorption studies were carried out. Equilibrium sorption results well fitted the Langmuir isotherm for both ions tested, showing a startling aptitude in arsenic (76.3 mg/g) as well as chromium (130.9 mg/g) sorption properties if compared with similar polymers as well as other materials. Exploiting its spongy nature, only 5 mins were needed to absorb contaminated medium releasing purified water by a simple squeezing. Most importantly, the sponge can be easily regenerated and reused again up to three times without the depletion of its efficiency.