Recycling of Industrial Effluents after Treatment Using Indigenous Sources: Agricultural Solid Wastes - Adsorption Dynamics

摘要

Industrial growth and associated technical sophistication in the last three decades or so has posed major problems of solid waste disposal. It has become essential either to find suitable ways for the safe disposal of the wastes or to suggest novel uses, considering them as by-products. Otherwise these will remain an accumulated waste, contributing highly to environmental pollution. The choice between recovery of valuable materials from waste and disposal of waste depends mainly on these factors: technology, economics and attitude. In developing countries like India, industries cannot afford to use conventional wastewater treatment chemicals like alum, ferric chloride, polymer flocculants and coal based activated carbon because they are not cost-effective. Among the treatment methods adsorption seems to be an effective method. An inexpensive and more easily available adsorbent would make the removal of pollutants an economically viable alternative. Agricultural wastes like waste orange peel, banana pith, coir pith and peanut hull are discarded in the agricultural sector. These waste contain cellulose and lignin, which act as very good adsorbents. Namasivayam and coworkers have investigated to recycle these agricultural solid wastes as adsorbents with and without modification for the treatment of industrial effluents. The biogas residual slurry has got a novel advantage, which acts both as manure and adsorbent. The biogas residual slurry contains both macro and micronutrients, which are essential to plants. The biogas residual slurry is an efficient adsorbent for the removal of dyes (1-5), toxic metals (6-8) and pesticides (9) from industrial effluents. Activated carbon made from peanut hull showed good adsorption capacity for the removal of toxic metals from industrial wastewaters (10-14). Physically and chemically activated carbons derived from coir pith (15) were found to be efficient for the removal of dyes (16, 17), phenols(18-20) and toxic metal ions (21-23) from industrial wastewaters. Waste banana pith (24-26) and waste orange peel (27,28) were capable of removing dyes and toxic metals from wastewaters. Surface modified biomass was found to remove anions(29). Results of batch mode adsorption studies using the above non-conventional adsorbents for the removal of heavy metals, anions, dyes and phenols and applications to the treatment of real/sythetic industry effluents will be presented in this lecture. Kinetics and temperature effects of adsorption will be discussed. In order to find out the suitability of any material as adsorbent, it is essential to evaluate its adsorption capacity and study adsorption dynamics, isotherms, pH effect and desorption.