PHYTOREMEDIATION: I. REMOVAL AND RECOVERY OF LEAD AND ZINC FROM DYEING WASTES BY ALFALFA BIOMASSP. SIVAKUMAR, R. RAFI MOHAMED, GEORGE JOHN AND K. VIJAYARAMAN
Dyeing and textile effluents of Karur, S. India, were subjected to phytoremediation, using powdered dry shoots of alfalfa (Medicago sativa), to assess the removal of heavy metals, lead and zinc. Coarsely filtered effluents were diluted with water (1:9). 2m1 each of the effluent was equilibrated in batches on a gyratory shaker with 200 mg alfalfa biomass. Equilibration was found to be optmized beyond 20 minutes contact time, at a pH between 6.0 and 7.0. Equilibration upto 10 cycles indicated maximum adsorption (Zn = 0.072mg/g; Pb= 0.00914mg/g). Up to 99% Pb and 82% Zn could be recovered from alfalfa biomass, when mixed and agitated with 2m1 of 0.1M HC1, for 30 minutes and repeating the process thrice, each time with fresh HC1. Phytoremediation with alfalfa immobilized in polysilicate avoided clogging at flow conditions. Immobilized biomass was packed in columns of 8 ml capacity and the effluent samples were passed through it continuously at a flow rate of 2 ml/minute. Up to the passage of 60 bed volumes of waster water, metals were completely adsorbed to the column, beyond which metals escaped the biosorbent in meagre amounts. With the passage of 15 bed volumes of 0.1 M HC1 through the metal adsorbed columns, 81% Pb and 64% Zn could be recovered. Results of the study revealed alfalfa biomass as a low-cost, efficient biosorbent for heavy metals. Easy recovery of the metals from the biosorbent and the potential for reuse were added advantages.
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