The comparison of the alkali-treated and acid-treated naturally mined Philippine zeolite for adsorption of heavy metals in highly polluted waters

Natural zeolite can be modified by single or combined treatment of heating and chemical modification using acids, bases, and inorganic salts. In this study, the Philippine natural zeolite (PNZ) was modified with alkali and acidic solution. The alkali-treatment and acid treatment used sodium hydroxide (NaOH) and acetic acid (CH₃COOH) as chemical modifier respectively. Various concentration of the solution (1M and 2M) and temperature (25°C and 50°C) was used during modification of the PNZ. The XRD of Na-PNZ and Ac-PNZ shows mineralogy of clinoptilolite and mordenite phases of the natural zeolite. The SEM images shows porous and plate-like morphologies of both modified materials. These property shows surfaces for adsorption of metals from wastewater solutions. The Na-PNZ and Ac-PNZ was used as adsorbents for the treatment of synthesized copper solution. The copper uptake of Na-PNZ from an aqueous solution is higher compared to the Ac-PNZ at 99.58%. The adsorption capacity sequence of the modified materials are as follows, 1M Na-PNZ > 2M Na-PNZ > 1M Ac-PNZ > 2M Ac-PNZ. The temperature used in the modification appears to have a significant effect on the adsorption capacity of the modified PNZ samples, the increase in temperatures resulted to a decrease in the uptake of copper.