Adsorption of Cyanide from Cassava Wastewater Using Calcined and Activated Oyster Shell Ash

Calcined ash and activated ash adsorbents were prepared from oyster shell. The physico-chemical properties of the prepared calcined oyster shell ash (COSA) and activated oyster shell ash (AOSA) were obtained using ASTM standards and Sears method. The results show that AOSA is a better adsorbent for removal of cyanide from cassava wastewater than COSA. The adsorption of cyanide from cassava wastewater onto adsorbents (COSA and AOSA) was investigated as a function of pH, adsorbent dosage, contact time, temperature and initial cyanide concentration. The batch study reveals that the adsorption process is strongly pH dependent and maximum cyanide removal is found to occur at pH of 10. The highest percent removal of cyanide from cassava wastewater was found at contact time of 80 minutes and 30oC. The effect of temperature on the adsorption process shows a small increase in the percent cyanide removal followed by a large decrease which suggests physical adsorption as the adsorption mechanism. The percent cyanide removal efficiency decreases with increase in initial cyanide concentration and increases with increase in adsorbent dosage.