Tea residue as a bio-sorbent for the treatment of textile industry effluents

Abstract

Tea residue, a common waste obtained from households and beverage industries, was studied as an efficient bio-sorbent for the extraction of methylene blue (MB) from textile industry effluents by varying key operational parameters such as pH, contact time and adsorbent dosage. Scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier-transform infrared spectroscopy (FT-IR) were used for the characterization of tea residue. This investigation found that the tea residue’s morphological structure and availability of selective functional groups are the main factors behind its high adsorption capacity. Adsorbent dosage and pH were found to be two important parameters that affect the efficiency of the adsorption process. Also, the contact time affected the removal efficiency of adsorbent—eventually reaching equilibrium after 105 min. The adsorbent has shown a maximum adsorption capacity of 181.2 mgg−1 at pH 10. The results showed that the equilibrium data fit the Langmuir isotherm very well and are best described by a pseudo-second-order kinetic model with a correlation coefficient of 0.99. For the mechanistic understanding of the adsorption transport process, the intraparticle diffusion model was used. In addition, the testing of experimental data for kinetic models was carried out by statistical analysis. The results of the FT-IR analysis showed that electrostatic interaction exists between MB and functional groups of tea residue. This study showed that the activated tea residue is not only a viable and economic alternative to other potential bio-sorbents and activated carbon but also has increased adsorption capacity and favorable kinetics.