Isotherm studies for determination of removal capacity of bi-metal (Ni and Cr) ions by aspergillus niger

Pakistan is among the developing countries where there is a need to establish new industries to meet the demands of a growing population. This has led to industrial setup in various sectors, without proper planning and consideration for treatment of contamination, leading to disposal of untreated wastewater into nearby land and water bodies. This study was planned to investigate an indigenous Aspergillus niger for development of biosorbent for the removal of metal ions. The Aspergillus isolate's Ni and Cr removal efficiency was determined in batch mode over various pH (4.0-10.0) and temperature (25-40 deg. C) as single as well as bimetal ions. Using a single metal ion, maximum biosorption potential was obtained at pH 5.0-6.0 and 30-35 deg. C for both ions. On the other hand, Ni removal was reduced in the presence of Cr, while Ni removal influenced Cr removal with an increase showing maximum removal at an initial adsorbate concentration of 50mg/L, pH 6.0 and 35 deg. C. Effect of presence of bimetal in a solution on biosorption potential of Aspergillus niger was predicted by using equilibrium modeling. Adsorption trends for both nickel (R2 0.9916) and chromium (R2 0.8548) followed Langmuir isotherm in single metal removal system, but under bimetal condition chromium adsorption fitted better to Freundlich model and that of nickel followed Temkin isotherm, suggesting considerable change in behavior and interaction between biosorbent and metal ions. Therefore, we concluded that Aspergillus niger a viable strain for development of a biosorbent for removal of a mixture of metal ions. (author)