ADSORPTION OF IMPURITIES FROM IRRIGATION WASTEWATER USING ACTIVATED CARBON PRODUCED FROM SELECTED BIOMASS

Abstract

Pollution from wastewater generated through irrigation has been a major challenge to environmental engineers (especially agricultural engineers) today, as a result of the contaminants and pollutants discharged due to the chemicals from the fertilizers used on crops and the discharge of sediments to surface water or groundwater. An approach to treating this wastewater necessitated the study on the preparation and production of activated carbon to serve as an adsorbent using groundnut shell for the treatment of wastewater from irrigation. Therefore, the aim of this study was to prepare activated carbon from groundnut shells for the treatment of irrigation wastewater. Wastewater samples were collected from Oke-Oyi irrigation scheme. The samples were analysed for initial physicochemical properties using the Food and Agriculture Organization of the United Nations (FAO) standard. Raw groundnut shells were collected from Ogbomoso. The initial analysis of the drainage water shows the water is highly alkaline and contains sulphate and nitrate above FAO benchmark values. The groundnut shells were grinded and sieved to obtain a 2 mm diameter particle size. The sample was carbonized at 400°C for 30 minutes and activated with 0.3M of phosphoric acid. The effects of temperature (20°C, 30°C and 40°C) and dosage of the activated carbon (1 g, 1.5 g, 2 g and 2.5 g), contact time (30 minutes, 1 hour, 1.5 hours, and 2 hours), and granulated activated carbon (GAC) on sulphate and nitrate removal were studied. The effect of the adsorbent on water pH was also studied. The characterization of the prepared AC and the determination of adsorption capacity were carried out. The surface morphological changes of the AC samples were investigated using a scanning electron microscope operated at 25 kV. Fourier Transform Infrared Spectroscopy (FTIR) was carried out to establish the functional groups present. At temperatures of 40°C, 30°C, and 20°C, the pH of the water decreased from 9.94 to 8.22, 8.22, and 8.26, respectively. The optimum dosage with 100% sulphate removal from wastewater (30 – 0.14 mg/l) was 2.5g at 20°C while the optimum dosage for nitrate removal (41.5 – 0.0813 mg/l) ranges between 1–2.5g at 20°C. The SEM analysis produced a well-developed porous surface on the micrograph of AC after chemical activation, which suggests improved removal of impurities when used. Therefore, the use of groundnut shells as feedstock for AC serves the dual purpose of good waste management and pollution treatment antidote.