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 N₂ 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.

In this work, kaolin processing waste (KW) and columbite–tantalite waste (CTW) from mining activities were used to manufacture sustainable self-supporting ceramic membranes using the freeze-casting technique. The wastes were characterized, and formulations using only wastes were developed. Gelatin was used in the freeze-casting as a processing aid to avoid dendritic or lamellar pores. The membranes were sintered at different temperatures (1100 °C, 1200 °C and 1300 °C) and analyzed by X-ray diffraction, scanning electron microscopy, flexural strength measurement, and mercury porosimetry. The flux through the membranes was measured using a gravity-driven dead-end filtration system. The membranes containing 80% KW and 20% CTW sintered at 1200 °C showed high porosity (59%), a water permeate flux of 126.5 L/hm², and a mechanical strength of 1.5 MPa. Filtration tests demonstrated effective turbidity removal (>99%) for synthetic water consisting of tap water and bentonite, reaching 0.1 NTU. The use of mining waste has shown considerable promise for the development of sustainable and affordable membranes for water treatment applications.