Evaluation of a pH-responsive guar gum-based hydrogel as adsorbent for cationic dyes: kinetic and modelling study

Abstract

Interpenetrating network of guar gum and polyacrylamide has been made by simultaneous polymerization and crosslinking. Two different crosslinkers have been used to control the network structure. The amide groups in the network have been subsequently hydrolyzed by controlled saponification to obtain different degrees of ionic content in the gel. The gels containing -NH 2 and -COOH functionalities have been characterized by FTIR, elemental analysis, DSC and TGA techniques. The swelling of the gel and pH responsiveness have been evaluated. The suitability of the gel as adsorbent material for removal of cationic dyes from aqueous solution has been investigated with crystal violet and azure B. The results revealed high degree of pH responsiveness and high dye adsorption capacity of gels. The adsorption-desorption processes were observed to be effective in repeated cycles, indicating the reusability of the gels for dye removal applications. The adsorption is observed to occur by Fickian diffusion and pseudo-second-order kinetic model appears to describe the adsorption. Crystal violet was absorbed to higher extent and bound stronger than azure B by the gel network. The adsorption is described by Langmuir model in case of crystal violet and Freundlich model for azure B. The thermodynamic parameters of adsorption indicate exothermic adsorption leading to ordered arrangement of dye molecules on the gel.

Smart Adsorbents for Aquatic Environmental Remediation

“…and polymer gums) containing pH sensitive groups and their nanocomposites are pH responsive materials that can be used for water purification. [141][142][143][144][145][146][147] pH-responsive adsorbents can be used for selective pollutant removal. For example, ammonium-functionalized hollow polymer particles (HPP-NH 3…”

“…azure B (AB) and crystal violet (CV). [141] The AB and CV adsorption occurred because of electrostatic interaction between the oppositely charged AB and CV molecules and guar gum-based hydrogel system. About 85 and 50% AB and CV were respectively released during desorption in NaCl solution.…”

“…Furthermore, CV adsorbed with a higher capacity and bound stronger than AB through the guar gumbased hydrogel network. [141] Figure 2. A) Graphic illustration of the adsorption/desorption process of a photo-regulated adsorbent which opened and closed upon light irradiation, B) Graphic illustration of molecular gates reversibly closed/opened because of photo-isomerization of azobenzene, C) methylene blue (MB) and D) brilliant blue (BB) adsorption curves on azobenzene (AZ)-functionalized mesoporous silica (MS) with and without UV light irradiation.…”

Recent approaches in guar gum hydrogel synthesis for water purification

“…One of the possible mechanisms followed in water purification is adsorption. For this, numbers of fillers and chemical modifications have been investigated to achieve required application in water remediation program [64], [65], [66], [67], [68], [69], [70], [71], [72]. Table 1 shows (Figure 2a).…”

Magnetic nanoparticles embedded in pectin‐based hydrogel for the sustained release of diclofenac sodium

“…The polysaccharide components in these macromolecular systems are often modified by grafting or by formation of an interpenetrating network with synthetic monomers. The chemical modification of polysaccharides such as alginate, hyaluroic acid, gum ghatti, cellulose, guar gum, starch, xanthan gum, gellan gum, dextran etc. has been attempted in recent years for development of systems with desirable properties for pharmaceutical, agricultural and industrial applications.…”