CO-REMOVAL OF PHENOL AND CYANIDE FROM WASTEWATER BY SIMULTANEOUS ADSORPTION AND BIODEGRADATION

Abstract

Recent industrial advances has led to an increase in pollution be it air, water or any other kind of pollution. Industries like iron and steel plant, electroplating, coke industries discharge a good deal of phenol and cyanide. These pollutants cause many kinds of skin problems, gastrointestinal disorders and even death. The present work concentrates on treatment of industrial discharge containing phenol and cyanide by simultaneous adsorption and biodegradation. The simulated synthetic wastewater is treated by various biosorbents in batch as well as continuous reactors for the co-removal of phenol and cyanide using simultaneous adsorption and biodegradation. Influence of various experimental parameters like pH, adsorbent dose, contact time, temperature and initial concentration have been studied and these parameters have also been optimised for increase in removal percentage. The mathematical modelling has also been done for the simultaneous adsorption and biodegradation process by using different adsorption isotherms, kinetic and thermodynamic models. The experimental data has been modelled using various multicomponent isotherm models. SAB process of phenol and cyanide are dependent of pH of the process. The optimum pH for the process for all the adsorbents comes out to be 7. The bacteria showed no visible growth in extreme acidic and extreme alkaline pH. Both pseudo first order and second order models were best fitted to the SAB process with all the three adsorbents. The equilibrium isotherms that were best fit were either non modified Langmuir or extended Langmuir for phenol adsorption onto the three adsorbents and the isotherms that best fitted cyanide data was modified Langmuir isotherm. There is not much change in the SAB process with increase in temperature. ΔG⁰ is negative showing the feasibility of the process. For rice husk SAB of phenol is an endothermic process with an increase in randomness at the solid/liquid interface but SAB of cyanide is an exothermic process with decrease in randomness at the solid/liquid interface. For corn husk leaves and egg shells SAB of both phenol and cyanide is an exothermic process with a decrease of randomness at the solid/liquid interface. RTD studies were also performed on the reactor which showed its behaviour to be close to plug flow. Column studies were carried out taking rice husk and granular activated carbon. Effective bed contact time of 5 h showed a higher removal percentage and column capacity for simultaneous adsorption and biodegradation in the GAC column. The 5 percentage removal of phenol and cyanide for the continuous GAC column by simultaneous adsorption and biodegradation was estimated as 99.99 %and 98.85 %. The percentage removal for co-adsorption of phenol and cyanide by regenerated GAC columns were 64.24 % and 73.12 %. The breakthrough curve obtained showed a better fit to the Adams Bohart and Wolborska Model. The percentage removal of phenol and cyanide for the continuous rice husk column by simultaneous adsorption and biodegradation was estimated as 81.43 % and 90.80