An Interpenetrating Polymer Network Hydrogel Based on Cellulose, Applied to Remove Colorant Traces from the Water Medium: Electrostatic Interactions Analysis

Abstract

The main objective of this work was the removal of eosin Y and green malachite from an aqueous medium by using a cellulose-based biodegradable interpenetrated network (IPN). The IPN was obtained by the sequenced synthesis method. In the first step, cellulose was crosslinked with epichlorohydrin (ECH). In the second step, the obtained gels were swollen in a reactive mixture solution, which was based on the monomers 2-hydroxyethyl methacrylate (HEMA) and 1,6- hexanediol diacrylate (HDDA). After this, swelling equilibrium was reached through the gels’ exposition to UV radiation. An infrared spectroscopy (FTIR) was used to analyze the bond stretching, which confirmed the IPN’s formation. The swelling kinetics in aqueous mediums with different pH values showed a high swelling at a basic pH value and a low response in neutral and acidic media. The IPNs showed an improvement in water uptake, compared to the networks based on PHEMA or cellulose. The IPN was used to remove dyes from the water. The results showed that a high percentage of green malachite was removed by the IPN in six minutes of contact time. The experimental results were confirmed by the docking/modeling method of the system (IPN/Dye). The different physical interactions between the IPN and the dyes’ molecules were investigated. The interactions of the hydrogen bonds with malachite green were stronger than those with eosin Y, which was in good agreement with the experimental results.

Preparation of cellulose-based composite hydrogels for the removal of methylene blue

“…According to the literature, at lower pH levels, the amount of H + ions increase, so an additional physical cross-linking would be formed, causing the hydrogel network to contract and decrease its swelling capacity; while, at higher pH levels, H + ions decrease and OH − ions increase 60 generating negatively charged sites that promote expansion and displacement of polymeric matrices, increasing the pore size of the network and improving the swelling capacity of the hydrogel. 61 However, these hydrogels presented swelling values at 25°C well below those of hydrogels based on cellulose derivatives reported in the literature: 550% and 725%. 62,63 Therefore, it is presumed that the presence of zinc, from ZnCl 2 used in the dissolution of cellulose, produced cellulose-zinc and starch-zinc complexes.…”

Removal of Malachite Green by Poly(acrylamide-co-acrylic acid) Hydrogels: Analysis of Coulombic and Hydrogen Bond Donor–Acceptor Interactions

“…The analysis of swelling in the copolymer hydrogels was conducted using distilled water with MG. Equation (2) [53,54] was utilized to compute the parameter ES, which represents the equilibrium swelling state after prolonged swelling periods.…”