A comparative study of the adsorption of azo dyes in mixed adsorbents composed of Aspergillus niger and Citrus sinensis chemically modified: Influence of pH

Abstract

The economic growth of the textile sector in Brazil has contributed to the generation of new jobs, qualification of the workforce and better living conditions for the population. However, due to the high activity of the sector, large volumes of toxic effluents have been generated which, if improperly disposed of, cause serious environmental damage. Therefore, alternatives in the treatment of effluents are interesting to increase the availability of this resource. A technique that has stood out, for being efficient, easy to operate and economical, is adsorption, a passive capture process where pollutants are deposited on the surface of materials. Thus, the work aimed to carry out a comparative study of the influence of pH in the removal of the dyes Remazol Black (RB), Remazol Red (RR) and Remazol Yellow (RGY) using different mixed adsorbents constituted by the fungus Aspergillus niger grown in orange peel in two different culture media. Six types of adsorbents (three for each culture medium) were produced and were treated with acid, base and without treatment. These were subjected to adsorption tests at different pHs (2, 7 and 9), using a solution (25 mg.L-1) volume of 100 mL, 0.5 g of biomass, rotation 150 rpm, 30 oC. The results showed that the adsorbents produced were able to adsorb the dyes RB, RGY, RR at different pHs. The best adsorption condition was obtained at pH 2 and the adsorbents were treated with acid, showing a promising alternative for the treatment of textile effluents.