Short communicationEnhanced removal of reactive navy blue dye using powdered orange waste

•We examined the removal of reactive navy blue dye from effluent using orange waste (OW) biosorbent.•FT-IR spectra confirmed that hydroxyl and carboxyl groups are the major active sites for biosorption.•The SEM analysis revealed obvious changes in surface morphology of OW after biosorption.•Optimum conditions were: pH 2, biosorbent doze of 4 g L−1, agitation speed 80 rpm and maximum dye removal was 82%.•Equilibrium and kinetic models showed that the adsorption process is monolayer and pseudo-second order.

The aim of the present research was to evaluate the suitability of low-cost, ecofriendly and freely available orange waste (OW) biosorbent for the removal of reactive navy blue dye. The biosorption potential of OW was investigated using synthetic solutions of textile dye (reactive navy blue) at different parameters, e.g. biosorbent dose, initial concentrations of solution, contact time, pH and particle size in a batch system. The optimum conditions were identified as contact time of 160 min, pH 2, biosorbent dose of 4 g L−1, agitation speed of 80 rpm and initial dye concentration of 100 ppm. The biosorbent was analyzed by surface area analyzer (SAA), Fourier transform infra-red spectroscopy (FT-IR) and scanning electron microscopy (SEM) for its physical and chemical characterization. The FT-IR spectra indicated that hydroxyl and carboxyl groups were major active sites for biosorption, while the results of SEM showed obvious changes in surface morphology after biosorption. Experimental data were fitted in Langmuir and Freundlich equilibrium isotherms and found to follow the Langmuir equation. Adsorption capacity was 30.28 mg g−1 with the dye removal efficiency of 82%. The application of pseudo-first order equation, pseudo-second order kinetics, Elovich sorption model and intraparticle diffusion kinetics revealed that pseudo-second order kinetic model best explained the experimental process. The results indicated that orange waste is a cost-effective and eco-friendly biosorbent and competitive to the current wastewater treatment technologies.