Smart and functional polyelectrolyte complex hydrogel composed of salecan and chitosan lactate as superadsorbent for decontamination of nickel ions

Abstract

Green and functional bio based adsorbents based on naturally derived polysaccharides have attracted considerable interest owing to their non-toxicity, biodegradability, flexible design, and wide origins. Here, smart polyelectrolyte complex (PEC SC1-SC4) hydrogels were developed by self-assembling of different ratios of salecan and chitosan lactate (CL) for clean-up of nickel ion (Ni2+) from wastewater. Preparation process was rapid and eco-friendly, without any toxic cross-linkers. The electrostatic attractions between polysaccharides were studied by FT-IR, XRD, XPS, and TGA. Particularly, the content of salecan and CL could be precisely modulated to tailor the swelling ability, micromorphology, and stiffness of the hydrogels. Ni2+ adsorption onto the hydrogels was dependent on salecan/CL ratio, pH, initial ion concentration, and contact time. SC4 showed the highest Ni2+ uptake, but it was too brittle. SC3 was selected for absorption studies. The equilibrium adsorption data commendably matched the pseudo-second-order and Langmuir models, demonstrating monolayer chemical adsorption mechanisms. The maximum Ni2+ adsorption derived from Langmuir model was 414.9 mg/g, superior to many reported Ni2+ adsorbents. Most strikingly, SC3 performed good recyclability, and the adsorption capacity still kept 95.3% even after five adsorption/desorption cycles. Hopefully, the prepared SC3 hydrogel is a potential agent for treatment of wastewater contaminated with Ni2+ ion.