Gypsum-based Porous Media Filter with Solid Waste: A Novel Composite for Removing Arsenic (III) from Aqueous Solution

Groundwater pollution from arsenic is one of the biggest hindrances for billions of people to get cheap and easy access to potable water. Searching for novel remediation techniques is prompted by the cost of installations and maintenance associated with existing purification technologies. Because of landfill issues and secondary pollution, solid waste from the construction and agricultural sectors is difficult to handle. In this study, a gypsum-based porous filter media block (PFMB) has been introduced which can be a cheap arsenic (III) removal technology introduced using agricultural and construction solid waste. The PFMB was made of gypsum (CaSO4) using aluminium sulphate (Al2(SO4)3), Ferric chloride hexahydrate (FeCl3.6H2O, Sodium bicarbonate (NaHCO3), bio-adsorbent and biochar prepared from waste vegetables. The physical properties of PFMB were evaluated, and hydraulic conductivity was found suitable for applying this in the water filtration system. In the column study using NaOH-treated PFMB, arsenic (III) removal was achieved 100% in the range of 0.1-1.0 mg/L. In batch experiments, the removal rate was more than 80%. Isotherms were evaluated as batch experiment was fitted with Langmuir isotherm and column study was compiled with Thomas model. The maximum adsorption capacity was for column experiments, 5.471 µg/g, and for batch experiments was 28 µg/g. Both the adsorbents and metal salts were found responsible for arsenic (III) adsorption. Variation of pH in adsorption was found insignificant. This PFMB can be used as filter media for arsenic (III) treatment in developing countries using solid waste.