Abstract

Thermally activated barks/stems and their ashes of Ficus religiosa, Cassia auriculata, Punica granatum and Calotropis gigantean are found to have remarkable affinity towards phosphate ions. The sorption characteristics of these bio-products towards phosphate from synthetically prepared waste waters have been studied with respect to various physicochemical parameters such as pH, sorption concentrations and equilibration times. Phosphate removal is found to be pH sensitive and also depends upon equilibration time and sorption concentration. Conditions have been optimized for the maximum extraction of phosphate; not less than 87% removal is noted in these sorbents. The sorption concentration needed for the maximum removal of phosphate is less for ashes of bark/stems than powders of bark/stem. The interferences of ten fold excess of foreign anions like chlorides, sulphates, nitrates, fluorides and carbonates are marginal. Cations namely Ca²⁺, Mg²⁺, Cu²⁺, Zn²⁺, Fe²⁺and Ni^2+, are synergizing the extraction of phosphate and hence % removal of phosphate is enhanced in their presence. The variations of D.O., BOD, COD, color and turbidity of the water samples after extractions  with the successful sorbents developed in this work, are found to be within the permissible limits of water quality standards.

Key words: Phosphate pollution control, bio-sorbents, Ficus religiosa, Cassia auriculata, Punica granatum and Calotropis gigantean.