ASSESSMENT OF EQUILIBRIUM TIME AND EFFECT OF CO-SOLUTES IN LINDANE SORPTION

The wood charcoal treated by 1N HNO3 (WCT) was used to remove toxic ch lorinated pesticide lindane (gamma-HCH) residue from water by the sorp tion process. The continuously mixed batch reactors (CMBR) were used t o study the effect of system parameters, such as initial sorbate conce ntration, sorbent size, and sorbent dose on the sorption equilibrium t ime of lindane by WCT. Using a rational approach an appropriate value of the equilibrium time was determined. The assessed equilibrium time from such an approach was found to be less than the value obtained by rough estimate which is commonly adopted in practice. The co-solutes o r co-sorbates, such as DDT and pentachlorophenol (PCP) imparted a mark ed decrease in sorption of lindane, whereas trichlorophenol (TCP) did not affect the removal pattern. WCT showed a preferential sorption of (i) DDT > lindane > alpha-HCH > beta-HCH and (ii) PCP > lindane > TCP. At a concentration greater than or equal to 20 mg/l of fertilizers, b oth urea and single super phosphate (SSP) significantly affected the r emoval of lindane. However, the effect was relatively higher by SSP th an by urea.