Biological Remediation of Cyanide in a Packed Bed SAB Reactor

Abstract

In the present study, the two most suitable natural bioadsorbents Prunus amygdalus and Tectona grandis leaves are screened on the basis of high removal capacity of cyanide and these bioadsorbents have been used for the cyanide removal from synthetic wastewater. Effects of process parameters like solution pH, agitation time, adsorbent dose, temperature and initial cyanide concentrations from synthetic wastewater have been investigated using the above adsorbents to determine the optimum process conditions for maximum removal of cyanide.To facilitate mathematical modeling adsorption kinetics models as well as adsorption isotherms have been developed. Adsorption of cyanide on almond shell and sagwan leaves has been found to follow pseudo 2 nd order kinetic model. Amongst the conventional isotherms, the Freundlich isotherm gives better prediction of specific uptakes for cyanide adsorption at equilibrium for almond shell whereas the Langmuir model is most suitable for sagwan leaves. Biological treatments with bacterial whole cells is another important route for cyanide removal from water in which whole cells are used either in bulk phase or are immobilized on a solid support. This process is termed as simultaneous adsorption and biodegradation process. Synthetic wastewater has also been treated in bio-column reactor using immobilized Bacillus cereus on almond shell bed. Effect of empty bed contact time and bed height of bio-column reactor bed on the removal of cyanide has been investigated. The percentage removal of cyanide by adsorption, biodegradation and simultaneous adsorption and biodegradation processes are analyzed separately and it is found to be 91.5, 95.8 and 99.6 percent removal of cyanide respectively at initial concentration of 100 mg per litre. Better removal efficiency of cyanide from synthetic wastewater is achieved by simultaneous adsorption and biodegradation processes followed by biodegradation and adsorption newline