Techno-economic assessment of waste mandarin biochar as a green adsorbent for binary dye wastewater effluents of methylene blue and basic fuchsin: Lab- and large-scale investigations

Treating polluted wastewater effluents on a large-scale requires the development of high performance and costeffective adsorbents. The recycling of waste mandarin peels, an environmentally friendly, and copiously available waste biomass into biochar (MRBC), has been approached. In the context of finding affordable and effective solutions for depollution of wastewater, MRBC was used for the adsorption of two dyes: methylene blue (MB) as well as basic fuchsin (BF) from their individual solutions and binary combinations. Batch adsorption studies were performed by employing the Box-Behnken (BB) design. The adsorption competency of dyes was analyzed to find the percentage removal (%R) and the adsorption capacity (q(e), mg/g). The dependent parameters (q(e) and %R) were determined as a function of pH, dose of MRBC (AD), contact time (CT), and concentration of methylene blue [MB]/ basic fuchsin [BF]. Removal of 98.14% of MB and 83.18% of BF was successfully achieved. Equilibrium experiments depicted that Langmuir and Freundlich models suit adsorption of dyes. The maximum adsorption capacity (q(max)) was 99.11 (MB) and 78.01 mg/g (BF), individually. However, when the dyes are combined, the q(max) decreased to 57.09 and 68.52 mg/g for MB and BF, correspondingly. The cost of MRBC was estimated to be similar to 4 USD/kg, while the overall cost of wastewater treatment was estimated to be 1.06 USD/m(3)/ year.