Isotherm Study in Arsenic Tolerant Bacteria Isolated from Arsenic Affected Area in West-Bengal, India

Abstract

Biosorption of arsenic and iron using arsenic tolerent bacteria i.e Bacillus sp. strain CCBAU 51490 (C-7) and Bacillus subtilis subsp. subtilis strain DSM 10 (A-2) isolated from halophilic arsenic contaminated soil of Baduria (Arsenic (As) concentration of the soil is 2.18 ppm.) after exposing them to 50 mg/l. and 30 mg/l of arsenic respectively and 42 mg/l. of iron (Fe) in primary and ternary solutions. The Langmuir and Freundlich adsorption isotherm models were used in the equilibrium modeling for determining the ideal condition for arsenic removal from contaminated sludge with this resistant bacterial consortium. Both the adsorption isotherm models were found to fit accurately with the experimental data. The best condition of the biosorption of arsenic by C-7 and A-2 bacteria are 700µl of the bacterial culture aliquot (3.612 x10 8 no. of cells of 0.0607 g. dry wt.) at pH 7 in 50 mg./l arsenic supplemented 30 ml. media at 37oC temperature and 300 µl of the bacterial culture aliquot (1.29 x 10 7 no. of cells of 0.019 g. dry wt. respectively) at pH 7 in 30 mg./l of arsenic concentration containing 30 ml. media at 37oC temperature , where the bacteria can take up 62.34% and 22.17% of As respectively. This condition satisfies both pseudo-first order and pseudo-second order rate kinetics graphs.The bacterial arsenic biosorption shows the different pattern in presence of iron i.e C-7 bacteria can uptake 47.08% of As from the ternary solution instead of 62.34% of As from the primary solution and A-2 can uptake 33.7% of As from the ternary solution instead of 22.17% of As from the primary solution after 24 hours.