A comparative study on the adsorptive efficiency of low-cost adsorbents for the removal of methylene blue from its aqueous solution

Abstract

Water pollution has become the greatest menace due to the discharge of effluent water from industries like dyeing, sugar, chemical processing, etc. The release of colored water containing dyes and heavy metals into the fresh water streams pollutes the water bodies and also penetrates deep into the soil making it unfit for use by human beings. In order to bring a solution to the water pollution problem, raw shot blasting dust (SBD) and phosphoric acid-treated activated carbon (PAC) prepared from putrescible vegetable waste (PVW) were selected as adsorbents. To evaluate the efficiency of both the adsorbents, Methylene blue (MB) was selected as the model compound. The composition and physico-chemical properties of both SBD and PAC were analyzed. Surface morphology was studied through scanning electron microscopy. FTIR studies were used in evaluating the presence of functional groups on the surface of the adsorbents. XRD analysis revealed that PAC is amorphous with few crystallite formations and SBD is crystalline in nature. The BET surface area, total pore volume, and pore widths were higher for PAC than SBD. The effect of pH, initial dye concentration, adsorbent dosage, and contact time were evaluated and optimum experimental conditions were verified. The adsorption of MB onto SBD and PAC follows pseudo-second-order kinetics. Langmuir and Freundlich isotherm models were applied to the equilibrium data and for both the adsorbents, Langmuir model fitted well. Economical evaluation and adsorption efficiency was done for both the adsorbents. From the present study, it could be concluded that the adsorption efficiency of PAC is better and SBD is more cost effective.

Keywords:

• Shot blasting dust
• Putrescible vegetable waste
• Methylene blue
• Langmuir isotherm
• Freundlich isotherm
• Adsorption efficiency