Study of the performance of lignin from cashew apple bagasse (Anarcadium occidentale L) as adsorbent for industrial synthetic dye

Abstract

The present work investigated the use of lignin from cashew apple bagasse and the lignin-magnetic nanoparticles composite in the removal of industrial textile dyes using the reactive turquoise blue dye, also named of reactive blue 21, as a model, and a real effluent. The adsorbents were characterized through FTIR and SEM-EDS. The influence of the pH, dye concentration, amount of adsorbent and temperature was evaluated in the adsorption process, analyzing the kinetic behavior and the isotherm of the process. The best adsorption results were obtained using lignin-magnetic nanoparticles (Lig-MNPs) as adsorbent. The acid pH favored the adsorption process and the amount of adsorbent that presented the best results was 8 mg/mL (approx. 70% of removal). The kinetic data and isotherm were best represented by the pseudo-second order model and Langmuir isotherm, respectively. The results obtained in this adsorption study demonstrated that the Lig-MNP composite poses as a potential adsorbent, presenting a removal percentage of up to 95% of the turquoise blue reactive dye; it can be reused for up to three cycles and its magnetic characteristics facilitate the separation process, reducing energy costs with filtration or centrifugation process. Also, Lig-MNPs adsorbs 58% (7.3 mg/g) of the concentration of dyes present in a real industrial effluent. The results obtained in this adsorption study compared with the results available in the literature demonstrate that the Lig-MNPs composite presents itself as a potential adsorbent of reactive dyes, and its magnetic characteristics facilitate the separation process, reducing energy costs.