Sorption of heavy metals from wastewater using ash from Water Hyacinth (Eichornia Crassipes)
Wafula, Dominic Mugeni
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Water hyacinth (Eichhornia crassipes) is an invasive aquatic weed that covers surface of freshwater lakes and rivers in the world. Due to the plant’s high rate of reproduction, it forms large colonies or mats on freshwater bodies thereby causing a variety of problems which include; hindering navigation of lakes and rivers, interrupting hydropower generation and water abstraction units. In addition, the aquatic weed depletes oxygen and nutrients rapidly from water bodies thus affecting growth of aquatic plants and animals like fish. Biological and physical control methods for water hyacinth on Lake Victoria have since been adopted. While the biological control methods have achieved a level of success, the physical control methods such as manual removal and mechanical control have had limitations, due to dumping of the removed weeds back into the lake or on the shores. This could prompt regrowth of the weeds. Considering the availability and potentially low cost of obtaining water hyacinth ash, its use as a biosorbent in wastewater treatment could be vital, especially in light of the reduced effectiveness of Nakivubo wetland in filtering out heavy metals from Kampala urban effluent prior to discharge into Lake Victoria. The main objective of this study was to investigate the use of water hyacinth ash in Sorption of heavy metals from wastewater. This was through determining; the characteristics of the water hyacinth plants obtained from Port Bell Luzira, the physiochemical characteristics of wastewater obtained from Nakivubo Channel and the Sorption efficiency of water hyacinth ash as biosorbent in the Sorption of Iron, Copper and Cadmium ions from wastewater. From the experiments that were performed in the laboratory according to (APHA, 1998), the moisture content of the water hyacinth was determined and found to be 92.89%, the water hyacinth plant had an ash content of 16.15% and a specific surface area of 179.8 m2 g-1 using Sear’s method. After incineration of the water hyacinth plants in a muffle oven at a temperature of 550 ℃ for two hours, the ash was treated with deionized water and used to treat the wastewater. From the Sorption studies, the treated WHA had a Sorption efficiency of approximately 92.18% for Fe and Sorption capacity of 1.1406 mg/g and 6.55 mg/g using the Langmuir and Freundlich isotherms respectively. From the results, it was concluded that the WHA has a high number of binding on to which the metal ion could get biosorbed and there is a possibility of using water hyacinth as an effective and low-cost method for Sorption of heavy metals from the wastewater.