Removal of synthetic rhodamine b from textile industrial effluent using cotton gin waste biochar

Abstract

Textile industries are one of the water consuming industries in Uganda and release a remarkable amount of organic dye compound containing wastewater. Almost 15% of dye compounds used in dyeing processes in textile industries enters the environment through wastewater and their existence in the waterways is unappealing to the eyes and hazardous to living organisms and environment thus causes a number of health and environmental problems because its toxic, mutagenic, and carcinogenic. Majority of textile dyes are not biodegradable and form complexes, common chemical water treatment processes such as coagulation, flocculation, and lime treatment are not effective methods for their degradation and is perceived to suffer from high costs, huge amount of sludge, and low efficiency. In this study, the effectiveness of the removal of RB dye using CGW biochar was assessed. The CGW biochar was synthesized in the laboratory by pyrolysis at a pyrolysis temperature of 250 and 5000C and used to adsorb RB dye without any chemical modification. The effects of different parameters such as surface area and porosity of the CGW biochar, pH of the textile effluent solution and the contact time on the adsorption process was studied. The CGW500 biochar exhibited a high removal capacity for all the selected textile dyes than the CGW250 biochar. Over 80% dye removal efficiency was observed for all the dyes at their respective optimal adsorption conditions using CGW500. The removal of RB dye by the CGW500 biochar was a strong function of the textile effluent solution pH and contact time. The CGW500 biochar exhibited a high removal capacity for RB dye at acidic pH 2 with adsorption capacity of 87.46%. The removal of all the selected textile dye was observed to be rapid within the first 15 minutes after which it increases slowly and achieved equilibrium at about 45 minutes. The study results were generally in good agreement with pseudo second order adsorption kinetic model signifying chemically aided adsorption process (chemisorption). The obtained results of the study proved and showed that biochar derived from cotton gin waste can be a very promising adsorbent for the removal of synthetic textile dyes from the textile industrial effluent mostly due to its low cost and environmentally appealing nature. However, for maximum performance, the CGW must be prepared at high pyrolysis temperature and pH enhancers should be added since the adsorption was strongly pH dependent.