Adsorption Studies On Removal Of Methylene Blue Dye Using Drinking Water Treatment Sludge From Water

Abstract

Wastewater generated by textile plants is linked to one of the major problems of water pollution. It contains a mixture of different dyes, auxiliaries, additives and additional chemicals that were added during textile production processes, causing serious environmental concerns. Focusing the environmental issue and economic point of view, the use of low cost and eco-friendly adsorbents has been investigated as an alternative to the current expensive method of removing dyes from wastewater. Drinking water treatment sludge (DWTS) was produced together with processed drinking water in a typical water treatment plant. A large amount of Alum derived DWTS was generated in Jimma city, such that disposal of the sludge and its beneficial reuse was concerned. In this study, Drinking Water Treatment Sludge (DWTS) particularly, Alum Sludge adsorbent (ASA) was used for the removal of Methylene blue (MB) dye from aqueous solution using batch adsorption process. Some Physico-chemical properties of the adsorbent were determined, such as surface area, surface functional group, surface crystal & point of zero charge. For optimization of the adsorption, the effect of contact time, effect of initial solution pH, adsorbent dosage & initial Methylene blue concentration were investigated. The surface area measured by Sear method was 43.8m2/g & point of zero charge was 6.23, for adsorbent. Untreated alum sludge adsorbent was characterized using by Fourier Transform Infrared (FTIR) & X-ray Diffraction (XRD). The equilibrium was achieved within an adsorption time of 60 min at the optimum pH of 7 & adsorbent dose of 5 g/L. In order to describe the relationship between the concentration of MB dye in the solution and the amount of MB dye adsorbed to adsorbent, Langmuir & Freundlich isotherm models were used for the equilibrium tests. The equilibrium data were best fitted to the Langmuir isotherm model (R2 = 0.942), the adsorption capacity (qmax) and efficiency (%) calculated from the Langmuir isotherm value obtained was 21.63 mg/g and 96.5% respectively. Pseudo-first-order and pseudo-second-order models were used to evaluate adsorption kinetics and it was found that the pseudo-second-order model data (R2 = 0.859) is the best described MB adsorption for adsorbent. From this study, DWTS could be reused, which is cost effective and environmentally friendly. Therefore, the application of DWTS could provide a solution for safe management of water treatment waste while providing a resource for water treatment.