Tailoring of carboxymethyl guar gum hydrogels via gamma irradiation for remarkable removal of cationic and anionic dyes from simulated solutions

Green hydrogels were synthesized from carboxymethyl guar gum (CMGG)-polyacrylic acid (PAAc) via gamma irradiation at doses of 10-40 kGy, they were codes as (CMGG/PAAc). FTIR spectroscopy was applied to confirm the chemical transformation of GG into the hydrogel formulations while the 1HNMR was employed to confirm the successful preparation of CMGG. TGA, XRD, and AFM were used to compare the improved formulation to native and CMGG. The investigated hydrogels were then applied comparatively to remove methylene blue (MB) and methyl orange (MO) dyes from aqueous solution under various operating parameters. In addition, the AFM was used comprehensively to address the adsorption process by comparing the surface topographies, height and roughness measurements between the dry and dye-loaded hydrogel. Four adsorption isotherms were investigated in order to go deep through the adsorption mechanism. These are Langmuir Freundlich, Redlich-Peterson and Jovanovich isotherms. Based on the values of R2 for all the models, it can be assumed that the Langmuir model is best appropriate for the adsorption process and that the dyes were adsorbed onto a homogenous surface. Kinetic tests showed that the pseudo-second-order model best fitted the adsorption process, with R2 values of 0.9999 for both dyes, confirming chemisorption as the rate-limiting step. The thermodynamic data indicates spontaneous, exothermic adsorption processes, with Gibbs free energy changes (Delta G) for MB ranging from -11.265 to -10.82 kJ/mol and MO from -3.221 to -3.323 kJ/mol. Negative enthalpy changes (Delta H) of -17.892 kJ/mol for MB and - 17.005 for MO show the exothermic nature of adsorption. The data proved effective removal of MB and MO dyes onto CMGG/PAAc hydrogels with better affinity for MB dye, making them excellent wastewater treatment adsorbents.