Remediation of aqueous solutions contaminated by benzidine toxic dye using non-conventional adsorbent: morphological and modelling studies

Abstract

Benzidine, a class A carcinogen, poses a significant threat in textile industry wastewater as it is a key intermediate in dye production. The promising adsorption technology using agricultural waste has proven to be an effective solution for water pollution. This study explores the potential of pineapple peels (the agricultural waste of little interest) as a low-cost adsorbent. Pineapple peels, typically discarded in massive quantities annually, exhibited a remarkable 91.064% maximum adsorption efficiency in a batch-type unit. This result was achieved at a pH, agitation speed, initial concentration, adsorbent dose, contact time, temperature, and particle size of 1450 rpm, 8 ppm, 3 g, 150 min, 20C°, and 88 µm, respectively. Morphological studies elucidated a surface area of 48.627 m2/g, retaining 11.25% post-treatment. Fourier-transform infrared (FTIR) tests highlighted various functional groups on the peel’s surface, undergoing alterations upon contact with benzidine. Scanning electron microscopy (SEM) examinations confirmed structural modifications post-adsorption. The adsorption process demonstrated spontaneity, low entropy, and exothermic behavior. Kinetic modeling revealed that the intraparticle diffusion model best represented the adsorption data. The isothermal behavior of adsorption was aptly described by the Langmuir model. The pineapple peels waste was tested to be a cheap rodenticide for laboratory rats and was found to be beneficial in disposing of these toxic residues. The results show a very good ability to eliminate the rodent with half the lethal dose, identical to that recorded in the literature. Thus, the study offers an economically viable and eco-friendly approach, aligning with the ethos of achieving zero-residue levels in waste management.