DECOLOURIZATION OF WASTE WATER BY ADSORPTION

Abstract

Among the various methods of colour removal adsorption has received great attention in the recent years as an efficient process for waste water treatment. Not only dyes but also other substances like heavy metals can be removed effectively by adsorption. Activated carbon is one of the commonly used adsorbent but it is very costly. In the recent past many low cost adsorbents were tried and found successful.Adsorption of Direct Blue dye was studied onto fly ash and coal in batch system using synthetic wastewater. The effect of contact time, dosage, dye concentration and pH was studied in batch experiments. It was found that when initial dye concentration is 100 mg/1, 25 gms/ 1 dosage of coal can remove 49% colour at contact time of-2 hrs. and 20 gms/1 dosage of fly ash can remove 65% colour at contact time of 1.5 hrs., at natural pH i.e. 7.5. It was also found that colour removal decreases with increasing initial dye concentration. At higher and lower pH adsorption was quite effective than at natural pH of solution. The equilibrium behaviour corresponds to the Langmuir isotherm for both the adsorbents and for both the initial dye concentrations i.e. 50 mg/1 and 100 mg/l. On comparing coal and fly ash it was observed that fly ash is much better adsorbent than coal for colour removal and is more economical also.