Performance of Activated Carbon Prepared from Sawdust as an Adsorbent for Endosulfan Pesticide

Abstract

Pesticides are used world over to protect crops. However, these are poisonous chemicals, and consuming water contaminated with pesticides exceeding safe concentrations could negatively affect human health. A study was conducted to investigate the effectiveness of sawdust carbon as an adsorbent for Endosulfan Pesticide. Laboratory batch experiments using sawdust carbon and commercial activated carbon were carried out. In each batch, 200 ml of contaminated water were mixed with 0.2 mg of carbon. Investigation was done on the effect of varying pH, agitation rate and contact time, and pesticide concentration, on pesticide adsorption capacity. Activated sawdust carbon was prepared by placing sawdust in a furnace at a temperature of 750oC for one hour. In order to activate the sawdust carbon, steam was passed through it for 30 minutes. Activation of sawdust carbon generated micropores. Iodine number was used to measure the extent of micropore development and iodine rate of adsorption was 658 mg/g of activated sawdust carbon. Once it was established that the activated carbon had capacity to adsorb the contaminant, batch experiments were done by mixing saw dust with contaminated water and sieving it so as to assess the rate of pesticide removal. Similar batches were prepared with commercial carbon for comparison purposes. The removal capacity reached equilibrium at different times depending on the initial concentration of the pesticide. For concentration of less than 30 mg/L, the equilibrium time increased linearly with pesticide concentration. When it was higher than 30 mg/L the equilibrium time remained constant at 250 minutes. The adsorption capacity increased with increasing initial solution pH, reaching an optimum at pH 7, after which time the adsorption capacity decreased with increasing pH. It also increased linearly with the rate of agitation and with increasing pesticide concentration, resulting in pesticide removal rate of higher than 95%. This compared well with commercial activated carbon. The results are best described using the Langmuir and Freundlich isotherms and pseudo first order kinetic adsorption models. Although many outlets are available for the utilization of wood fines, economical disposal of sawdust, shavings, and waste chips remains a problem of growing concern to the wood industry. Piles of sawdust (which can result to fire) are normally sited next to timber industry. Saw dust particle blown up by wind result to pollution of the environment. Disposal of sawdust waste in water bodies also result to adverse effects on the aquatic life. There is therefore need to continually invent methods of using sawdust waste. The study concluded that activated carbon prepared from sawdust can be used as an alternative adsorbent for pesticide removal. Further research is required on the disposal of used carbon to ensure that it doesn’t create new environmental problems such as release of toxics into the air, water and soil.