چكيده به لاتين
More concentration of heavy metals have been released in environment due to industrial, agricultural and technology developments in recent years. Accumulation of these metals in food chain and its stabilization in nature threatens societies economically and healthily. Copper has many applications in industry, but excess amount of it will cause toxication. According to several surveys, maximum allowed copper concentration in drinking water is 1.5 mg/l. Convenient methods for removing metal ions from aqueous solutions include physical, chemical and biochemical methods. Biosorption method, among others, as an option which is either economical and ecofriendly, has been highly regarded. In this research, biosorption of copper as a heavy metal by different biosorbents has been investigated. Experiments were carried out in three steps: (1) selecting the most suiting biosorbent, considering effect of pretreatmenting, and effecting factors on biosorption of copper by appropriate biosorbent; (2) studying optimized condition for absorbent’s recovery and conducting reusing of this absorbent; and (3) studying and comparing of equilibrium data with convenient isotherm equations. In first step, among three microorganisms, Bacillus subtilis was chosen as most suitable microorganism. In the following, effects of different factors (such as biosorbent concentration, contact time, pretreatmenting effect, and initial concentration of metal, biosorbent state and pH) on biosorption process of copper were examined using one factor at a time method. As a result, absorption capacity with copper initial concentration of 100 ppm was around 175 mg/g for 0.2 gr/l of inactive biosorbent at pH 5 and 30 min. In next step, effect of two trigger solutions on recovery of biosorbent and the reusing of recovered biosorbent were examined. Eventually, equilibrium data were fitted to Langmuir, Frendlich and Dobinin-Radushkevich equations and it was found that Frendlich isotherm has better accordance with biosorption of copper by B. subtilis. At the end, data fitting with adsorption kinetics resulted in compliance of copper biosorption from pseudo-second-order kinetic model.
