Saima Mirza, Muhammad Akmal and Zia Ur Rahman Farooqi
Chromium (Cr) is a toxic and carcinogenic element. The discharge of Cr into the environment has become a problem of great concern all over the world including Pakistan since few decades. Present research was conducted to study the biosorption of total Cr using two strains of algae Chlorella and Scenedesmus. Water quality indicators like chemical oxygen demand (COD), biological oxygen demand (BOD), pH, electrical conductance (EC), total dissolved solids (TDS), amount of suspended solids and Cr content were analyzed before and after the algal sorption. All these indicators were found beyond the permissible limits recommended by Punjab Environmental Quality Standard (PEQS) for irrigation, except pH of waste effluent which was 6.8 that is considered safe for disposal. Algal strains Chlorella and Scenedesmus were multiplied in an aquarium at different pH (6.5, 7, 7.8, and 8) to assess the growth response. After 26 days, growth equilibrium was achieved. After 23 days, maximum number of cells was examined at pH 7.8 using microscope. Cells count was 28X105. While growth of scenedesmus attained equilibrium after 26 days at same pH and total number of cell count was 20X105. Carbon activate algae granules (CAAG) was prepared using 0.1 N HCl solution for 24 hour stay in continuous stirring conditions. Effect of sorbent dose (5, 7 and 9 g) and contact time (0, 20, 40, 60, 80, 100, and 120 min.) were evaluated using Atomic Absorption Spectrophotometer (AAS). Results revealed that the maximum adsorption of Cr was after 90 min. using 9.0 g of Chlorella biomass. While Senedesmes took 120 min. with same dose of sorbent. Whole experiment was carried out at room temperature. Results revealed that maximum biosorption efficiency of 9.0 g CAAG was found at 90 min. which showed 97 % removal of Cr from leather effluent.
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