Congo Red (cr)Removal from Aqueous Solution by Commercial and Laboratory Prepared Low Cost Adsorbents Using Adsorption

Abstract

Release of dyes into the environment from industrial practices is a matter of global concern.Dyes are emitted from industrial plants in the form of aqueous effluents. They are widely used in several industries like textile, dyeing, paper and pulp, tannery, paint industries etc.Dyes are considered an objectionable type of pollutant because they are toxic in nature. Their classification can be done based on their usage, group and solubility. Various treatment processes used for the removal of dyes include adsorption, microbial degradation, wet air oxidation, etc. Use of commercial and low cost adsorbents is a viable option for dyes removal from aqueous effluents. However, high cost of commercial adsorbents like activated carbon and others, and material losses during their regeneration pose an impediment in the utilization of commercial adsorbents. This has led to a search for cheaper alternative materials as adsorbents such as lignin, bagasse pith, peat, saw dust; coal fly ash; rice husk ash and Bio-fuel extract (BFE), etc. The present study is therefore, aimed to study the process of adsorption of Congo red (CR) onto powdered and granular-activated carbon (PAC & GAC),and indigenously prepared low-cost adsorbents such as Bagasse fly ash (BFA), Rice husk ash (RHA), coconut Ash (CCA), Fruit juice extract (FJE), BAEL (Aegle marmelos) and spent tea (ST) and to find out the possibility of using them as low-cost adsorbents for the removal of dyes in general and CR in particular.This investigation also examines the influence and optimization of various process parameters for their optimal performance
such as initial concentration of CR (C0) contact time (t), temperature (T), and initial pH of dye solution. Batch adsorption experiments for the removal of CR from the aqueous solution by PAC, GAC, BFA, RHA, CCA, FJE, BAEL and ST were performed by using Taguchi design methodology.
Factors as such pH, temperature, adsorbent dose and contact time were optimized with the bigger-isbetter S/N ratio as quality characteristics and analysis of variance with 25 sets of experiments only. The optimum CR removal experimental conditions are obtained for all the adsorbents used with respect to their maximum uptake capacities in the present work. Moreover, the adsorbents were also characterized for their valuable adsorbable properties like surface area and point of zero charge.
The exhausted low-cost adsorbents along with the sorbed CR can be separated from the solution (by filtration), dried and used as such or as fire briquettes to recover their energy value. The resulting bottom ash blended with cementations mixture can be used for making building blocks or it may be used to make fire bricks.