Industrial sludge based adsorbents/ industrial by- products in the removal of reactive dyes -A review

Adsorption has been an effective separation process for non-biodegradable pollutants. Study of recovery of dyes reveals adsorption as an efficacious process. Many textile industries use commercial activated carbon for the treatment of dye waste. The current research is focused on the need to alternate commercial activated carbon with a cost effective, potential adsorbent. The major limitations in using commercial activated carbon in large scale are its regeneration and high cost of operation. Many researchers have studied the feasibility of using low cost adsorbents derived from natural materials, industrial waste materials, agricultural products and biosorbents as precursors. Numerous works have been reported on these adsorbents being used in the removal of heavy metals and dyes. This paper reviews the development of different industrial sludge/by products as adsorbents under various activation methods. The decolourization of reactive dye solutions by the developed adsorbents under batch mode is also discussed. Based on the reviews, development of activated carbon from preliminary tannery sludge is suggested by various activation methods

Adsorption of reactive dyes from aqueous solutions by tannery sludge developed activated carbon: Kinetic and equilibrium studies

Adsorption kinetic and equilibrium studies of two reactive dyes, namely, Reactive Red 31 and Reactive Red 2 were conducted. The equilibrium studies were conducted for various operational parameters such as initial dye concentration, pH, agitation speed, adsorbent dosage and temperature. The initial dye concentration was varied from 10 - 60 mg/L, pH from 2 - 11, agitation speed from 100-140 rpm, adsorbent dosage from 0.5 g to 2.5 g and temperature from 30 °C -50 °C respectively. The activated carbon of particle size 600 μm was developed from preliminary tannery sludge. The dye removal capacity of the two reactive red dyes decreased with increasing pH. The zero point charge for the sludge carbon was 9.0 and 7.0 for the two dyes, respectively. Batch kinetic data investigations on the removal of reactive dyes using tannery sludge activated carbon have been well described by the lagergren plots. It was suggested that the Pseudo second order adsorption mechanism was predominant for the sorption of the reactive dyes onto the tannery sludge based carbon. Thus, the adsorption phenomenon was suggested as a chemical process. The adsorption data fitted well with Langmuir model than the Freundlich model. The maximum adsorption capacity(q0) from Langmuir isotherm were found to have increased in the range of 23.15-39.37 mg/g and 47.62-55.87 mg/g for reactive dyes reactive red 31 and reactive red 2, respectively