Adsorption efficiency of coconut shell-based activated carbons on colour of molasses, oils, dissolved oxygen and related parameters from industrial effluent

Abstract

The adsorption efficiency of FeCl3, CaCl2 and K2CO3-activated carbon for the 500μm particle size produced from previously carbonized coconut shell on some adsorbates obtained from an industrial effluent and wastewaters as well as the colour of molasses has been studied. The adsorbates include oil and grease, dissolved oxygen (DO); biochemical oxygen demand (BOD) and chemical oxygen demand (COD), dissolved and suspended solids as well as total solids present in an industrial effluent sample. A colour comparator was used to determine the colour of the molassess, volumetric analysis was used to determine oxygen and related parameters while oil and grease were determined by gravimetry. The results showed that the activated carbons used in this study are capable of reducing the level of colour present in molasses and amount of oil/grease from a textile effluent. Ninety two and 97.4% of molasses and oil/grease respectively can be adsorbed onto 500μm particle size of ZnCl2 – activated carbon at room temperature. Out of the four activated carbons, (FeCl3-Ac, CaCl2-Ac, ZnCl2-Ac and K2CO3-Ac,) the FeCl3-Ac is most effective in adsorbing the dissolved oxygen, chemical oxygen demand, biochemical oxygen demand, dissolved, suspended and total solid present in a sample of a textile effluent. The FeCl3-Ac is more effective in adsorbing the solid impurities than the oxygen demands but least effective in adsorbing dissolved oxygen. There is a high correlation coefficient between the oxygen parameters and solids present in the effluent. This shows that the greater the amount of solids in an effluent the more the amount of oxygen required for biochemical and chemical processes. ZnCl2-activated carbon most effectively adsorbed 92.2% colour of the molasses while the FeCl3-activated was most effective in
adsorbing 94.3% of oil/grease, 46.2% of dissolved oxygen, 71.9% of BOD, 72.1% of COD and 96% each of dissolved solids (DS), suspended solids (SS) and total solids (TS). The coefficients of correlation found between each of DO, COD or BOD and DS, SS and TS adsorbed were 0.999, 0.907 and 0.763 respectively.

Key words: Coconut shell, activated carbon, adsorption, oxygen demand, solids.