Remediation of Water Contaminated with Cr6+ and Cd2+ Using Aluminophosphates Derived from Ashes of Tea Leaves and Pumpkin Seeds

Abstract

Access to clean water is an ever increasing challenge that is not only fuelled by climate change and phenomenally growth in population but also by pollution by heavy metals arises from many sources that include automobiles, purification of metals, smelting industries, paint industries and textile industries. Water pollution is on the increase owed to industrial development and population increases. Commercial adsorbents frequently used as adsorbents in water remediation remain expensive out of reach to majority low income earners. It is therefore essential to develop cheap adsorbent materials capable of removing Cr⁶⁺, Cd²⁺ ions and turbidity from wastewaters. Tea leaves ash (TLA) and pumpkin seeds ash (PSA) was used to generate aluminophosphates materials by hydrothermal reactions for removal of selected heavy metals from contaminated waters. Two adsorbents A and B were also prepared by varying ratios of TLA and PSA. Material A, (APA) was prepared by mixing TLA and PSA as in ratio of 1:1 while material B, (APB) was prepared by mixing them in ratio of 1:2. X-Ray diffraction was used for phase identification and characterization of synthesized material. The effects of metal ion concentration, initial pH, contact time, temperature, shaking speed and dosage on percentage removal of Cd⁺², and Cr⁺⁶ were determined. The equilibrium adsorption data fitted best in Langmuir isotherm model, as it had the highest value of correlation coefficient. Maximum monolayer adsorption capacities were 45.45 mg/g for cadmium and 50.00 mg/g for chromium using APA. Adsorption capacities of APB were 40.00 mg/g for cadmium and 41.67 mg/g for chromium. Based on adsorption capacities, APA was a better adsorbent than APB. The results from this study shows agro based aluminophosphates are potential adsorbents for remediation of heavy metals from waste waters.

Keywords: Adsorption isotherms, Heavy metals, Aluminophosphates, Wastewaters, Adsorbents