Aluminophosphates derived from tea leaves and pumpkin seeds ashes for removal of sellected heavy metals from contaminated water
Maingi, Mukora Francis
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About 43% of people in Kenya have no access to clean water. Lack of clean water may worsen as industrial development and population increases as projected if drastic measures are not taken immediately Pollution of water by heavy metals arises from many sources but most commonly from purification of metals, smelting industries, paint industries and textile industries. Activated carbon and other commercial adsorbents are frequently used as adsorbents. Despite their extensive use in water and wastewater treatment, these methods remain expensive. To reduce the problem of clean water scarcity, it is important to develop cheap adsorbent materials to remove heavy metals and turbidity from wastewaters. In this study, tea leaves ash (TLA) and pumpkin seeds ash (PSA) were used to prepare aluminophosphates adsorbent materials for removal of selected heavy metals from contaminated waters. These plant materials were collected from Muranga and Molo. Tea leaves was ashed at 400 ⁰C and pumpkin seeds at 800 ⁰C and resulting ash analysed using energy dispersive x-ray spectroscopy. TLA was found to contain about 30.1% of aluminium oxide and PSA contained about 37.0% of phosphorous (V) oxide. 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 1:1 while material B, (APB) prepared by mixing them in ratio of 1:2. X-ray diffraction was used for phase identification and characterization of synthesized materials. APA was found to contain , kaolinite, smectite and ilitite while adsorbent APB contained , , kaolinite, ilitite and smectite. Batch adsorption experiments were carried out to optimize the effect of initial metal ion concentration, initial pH, contact time, temperature, shaking speed and adsorbent dose on percentage removal of Pb2+, Cd2+, and Cr6+ using the aluminophosphate adsorbent. Column studies were carried out to determine effect of dosage on percentage removal of turbidity. The experimental data was fitted in Langmuir and Freundlich isotherms and was found to fit best in Langmuir isotherm, as it had the highest value of correlation coefficient. Adsorption capacities obtained from linearized graphs were 45.45 mg/g for cadmium, 91.91 mg/g for lead and 50.00 mg/g for chromium using APA. Adsorption capacities using APB were 40.00 mg/g for cadmium, 50.00 mg/g for lead and 41.67 mg/g for chromium. Based on adsorption capacities, APA was a better adsorbent than APB. The results from this study shows that agro based aluminophosphates are potential adsorbents for remediation of heavy metals from wastewaters.