Biosorption of methylene blue by activated sludge

The ability of the use of dried activated sludge for removing methylene blue (MB) was investigated. The dye binding capacity of biosorbent was shown as a function of initial dye concentration, initial pH, and temperature at agitation rate 700 rpm. The experimental results indicated that the equilibrium between the dye and the adsorbent in the solution was established within 30 min and the maximum % removal value was found as 96.54% at pH 7.5. The uptake biosorption increased with increasing initial MB concentration. The maximum MB adsorption capacities were obtained at the temperature of 30°C. The equilibrium data fitted very well to the both Freundlich and Redlich–Peterson adsorption models with high correlation coefficient (R2 > 0.99). The pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data, consequently; the results showed that the dyes uptake processes followed the pseudo-second-order rate expression. So, it can be concluded that dried activated sludge could be a potential low-cost biosorbent for the MB removal from aqueous solutions.