Isothermal and Kinetic Studies for the Removal of Malachite Green and Congo Red Dyes Using Wastes from Mining and Processing Perlite in Different Particle Sizes as Sustainable Adsorbents

Perlite waste materials with different particle sizes were evaluated as potential candidates for removing the malachite green (MG) and Congo red (CR) dyes from contaminated water. Two types of waste, referred to as coarse (CP) and fine (FP), with particle sizes of 0.075 mm, 0.045 mm, and 0.037 mm, were used. The samples were characterized using X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy, and N 2 adsorption/desorption. The adsorption efficiency of MG and CR was investigated by varying the parameters of pH, contact time, and initial concentration. The reduction in particle size significantly influenced the removal of the CR dye, leading to an increase in the adsorption rate of 23.9% and 45.5% for CP and FP, respectively. Conversely, the adsorption of the MG dye on the residues was not affected by different particle sizes. CP and FP exhibited a removal rate exceeding 70% for both dyes. The adsorption of MG and CR on the wastes was well-described by the Sips isotherm model. The results of adsorption kinetics were best fit by the Elovich model. Perlite waste materials have demonstrated significant potential for the adsorptive remove of cationic and anionic dyes from aqueous solutions.