Assessing the effectiveness of bio adsorbent in cadmium removal from industrial wastewater :

Abstract

Water is among the natural resources needed for germination of crops, to achieve sustainable food production via irrigation (Hristov, 2014). Various forms of anthropogenic activities contaminate this natural resource when humans engage in industrial activities to manufacture end-products for consumption (Abdulla et al., 2019). This adversely affects the water and makes it unsuitable for agricultural purposes (fishing and irrigation). Sewage sludge and industrial effluents discharged into water bodies contain contaminants. Among these are heavy metals such as cadmium, lead, chromium, mercury and arsenic, whose presence at low concentrations stunts plant growth by altering its biochemical and physiological development, leading to chlorosis, root growth inhibition and plasma membrane damage (Bouazizi et al., 2010; Mkadmi et al., 2018; Nagendrappa et al., 2010). Declining plant growth decreases yield, which affects food supplies. Remediation of heavy metal contaminated water is thus important for food security. The FAO and World Health Organization (WHO) recommended safe limits of Cadmium concentration in waste water and soils for agriculture is 0.003ppm and 0.005mg/l for drinking water in Uganda. The purpose of this study is to use a blended mixture of Groundnut shell and Water hyacinth made into biochar as a potential adsorbent for removal of cadmium in industrial waste water. Parameters like adsorbent dosage, pH and contact time were studied by a series of batch experiments at room temperature to determine the optimum procedure of the greatest Cadmium removal in the industrial waste water. The adsorbent dosage was varied between 2g and 6g with an interval of 2g, contact time between 30minutes and 60minutes with an interval of 15minutes and finally pH values from 2 to 8 the percentage removal of Cadmium was found to increase with the increasing dose of adsorbents and contact time whereas the percentage removal of Cadmium was found to decrease with the increase in pH value greater than four. The optimum conditions were determined using Orthogonal array of Taguchi experimental design with L9 three- level responses. The maximum removal efficiency values (90.94% Cd 2+) were obtained at pH 6 in 45 min with 6 g of blended biochar.