Abstract:
Biosorption is the most promising technique to decolorize, separate, and pre-concentrate liquid and gaseous mixtures to facilitate the removal of harmful chemicals because of its efficacy, easy operation, non-toxicity, and mild reaction condition. The present study was carried out to assess the efficacy of coffee husk in the biosorption of reactive Congo red dye. Coffee husk samples were collected from coffee shop in Harar City, Ethiopia. The biosorbent materials were prepared from raw and acid treated coffee husk powder. The functional and micromorphological characterization of the biosorbent materials were carried out by Fourier transform infrared spectrophotometer (FTIR) and scanning electron microscopy (SEM), respectively. The optimization of factors affecting the biosorption of the reactive dye were conducted for parameters including pH, adsorbent dos, contact time, and initial concentration of the dye. The result of FTIR indicated that a functional group that is typically found around 3745cm-1 in FTIR spectra of acid treated coffee husks is the O-H stretching vibration of hydroxyl (-OH) groups; and C-N starching vibration of the primary amine that is found in acid treated coffee husk at wave length 886cm-1; the wave number in 821cm-1 before and 876cm-1 after biosorption in the infrared (IR) spectrum was the C-H binding vibration of the aromatic compound. The spectra in the raw coffee husks FTIR result in a large band in the range between 3374cm−1 to 3436cm-1 indicating the existence of O-H stretching vibrations of cellulose, pectin, and lignin and -NH groups on the biosorbent surface. Scanning electron microscopy images have clearly shown that the acid treated CH biosorbent material exhibited a uniform interconnected structure with a continuous darker surface color. After dye absorption, the walls of biosorbent material have become fragile, irregular surfaces with the appearance of brighter colors due to the accumulation of the dye. The effect of the pH of raw and acid treated coffee husk on the absorption of reactive Congo red dye presented maximum removal of dye 90.79% for acid treated coffee husk and 80.68% for raw coffee husk at pH3. The effect of contact time of raw and acid treated coffee husks on the adsorption of Congo red dye has recorded the highest dye removal 89.19% for acid treated at 120 min and 81.48% for raw coffee husk powder at 150 min. The effect of the adsorbent dosage of raw and acid treated coffee husk on the removal of Congo red dye demonstrated the maximum adsorption 91.43% for acid treated coffee husk, and 80.60% for raw coffee husk at 0.6gm biosorbent dose. It can be concluded that the acid pretreated coffee husk biosorbent material was found to be more effective than an untreated raw coffee husk. The study emphasizes the potential for using coffee husk waste materials as efficient and sustainable solutions for water treatment. Further research could explore optimizing operating parameters and applying coffee husks in real-world dye wastewater treatment systems