Production of coffee husk based activated carbon for dye removal from wastewater

Abstract

The demand for activated carbon is increasing due to the increased effectiveness of the carbon materials in wastewater treatment. The objective of this research was to assess the performance of coffee husk activated carbon in treatment of dye wastewater. Coffee husks were selected because of their high carbon content and abundance in the country. Dried coffee husks were crushed to particle size of 750 µm sieve size to reduce the consumption of activating agent and were then subjected to different preparation variables such as impregnation ratio, carbonizing temperature and carbonizing time. The Response Surface Methodology (RSM) based on Central Composite Design (CCD) was used to optimize the preparation variables with percentage yields of activated carbon and dye removal as the targeted responses. The optimal conditions for the preparation of activated carbon using design expert software were 453oC, 61 minutes and 1.8 impregnation ratio. These set of conditions gave activated carbon yield of 43.3% and methylene blue removal of 85.8%. Analysis of Variance (ANOVA) for activated carbon yield and methylene blue dye removal showed the developed model equations were significant (p ≤ 0.05). The experimental and predicted values of activated carbon yield and methylene blue dye removal were in close agreement with correlation coefficients (R2-values) of 0.9703 and 0.9767 respectively. Characterization results showed low: moisture content (6.05%), ash content (2.48%) and volatile matter (28.46%) which indicated that produced coffee husk activated carbons were excellent adsorbent material to be used in bed reactors. Generally the results show that coffee husk activated carbon is a good adsorbent material for dye wastewater treatment.