Studies on Low cost Bio-Adsorbent in Wastewater Treatment

Abstract

Environmental pollution is a great concern in now a day. In modern time, with civilization and industrialization environmental pollution increases. Effluents of textile and dyeing industries pollute the environment directly and indirectly as well. Adsorption is one of the versatile techniques of removing waste. In the present investigation LBS Lima Bean Seed (LBS) (locally known as Rukuri in northern zone of Bangladesh) powder has been used as adsorbent for the removal of three textile reactive dyes, namely Reactive Magenta HB (RMHB), Active Orange P2R (AOP2R) and Reactive Red ME6BL (RRME6BL). It is observed that removal efficiency of RMHB, AOP2R and RRME6BL is high at lower pH (acidic medium). Though AOP2R and RRME6BL adsorbed at pH 2.0 and pH 3.0 respectively but in case of RMHB, it adsorbed relatively at higher pH, 6.0. Effect of concentration, adsorbent dose and contact time on adsorption process was observed. Removal of dyes increases with amount of adsorbent and time. But at in case of lower initial dye concentration dye removal rate was faster. Equilibrium time for the adsorption process was about 120 min. From the isotherm study it is observed that the applicability of the linear form of Langmuir and Freundlich model to LBS was confirmed by the high correlation coefficient R2 > 0.97. This suggests that the Langmuir isotherm and Freundlich models both provide good model of the sorption system. The value of 1/n was lower than 1, (n is greater than 1) indicating that studied dyes were favorably adsorbed by LBS. During the kinetics study it is seen that the plot of pseudo-first order has a high correlation coefficient than the plot of pseudo-second order. It should be mentioned, in both cases the value of R2 is close to the unity. More over the values of amount of adsorbate at equilibrium, qe dramatically differ from the experimental values in case of pseudo-second order. So, the adsorption of tested dyes on LBS is more appropriately followed the pseudofirst order model when compared with that of the pseudo-second order model. Study of Intraparticle diffusion model suggested that Intraparticle diffusion is not only Solo Rate Limiting Step.