A green physically crosslinked guar gum-phytic acid-gelatin composite for competitive adsorption of cationic and...

Herein, a composite, GG-PA-GL synthesized by integrating guar gum (GG), with biopolymer gelatin (GL) and the bio-based molecule, phytic acid (PA), following a robust and sustainable design strategy is reported. In the as-synthesized composite, PA with twelve terminal -OH groups forms hydrogen bonding with the -OH groups of GG at one end and the -OH, -NH₂, and -COOH groups of GL at the other, resulting in a well-integrated structure. The composite was characterized by FTIR, XRD, TGA, FESEM, EDX, point of zero charge, zeta potential, and BET analyses, and investigated for removing cationic (malachite green and basic fuchsin) and anionic (methyl orange and Congo red) dyes from their mixture solution. Adsorption behaviour for the dye mixture solution was studied in a parametric framework of time, temperature, pH, and initial dye concentration. The maximum efficiency of the composite for dye mixture solution was 94.24% at 35 °C and pH 7.0 within 120 min. The pseudo-second-order kinetic model and Langmuir isotherm model best described the adsorption for the mixture solution with a maximum adsorption capacity of 267.43 mg g^-1. The minimal values of error functions (χ², root mean square error, and normalized standard deviation) validated applicability of both the models. The composite demonstrated exceptional regeneration and reusability for dye mixture solution, for seven cycles, with a cumulative adsorption capacity of 507.3 mg g^-1. Owing to sustainability, environmental friendliness, and high efficacy, the composite showed strong potential for removing both cationic and anionic dyes from complex dye mixture as well as real wastewater.