Biossorventes lignocelulósicos de resíduos agroindustriais na remoção de contaminantes aquáticos: mecanismos, modelagem cinético-isotérmica e a fronteira dos compósitos magnéticos — uma revisão integrativa

Abstract

Aquatic contamination by potentially toxic metals, synthetic dyes and organic micropollutants remains one of the most stubborn environmental liabilities of our time, particularly in countries with intensive agroindustrial activity. Faced with the limitations of conventional treatment plants, biosorbents derived from lignocellulosic residues — bagasses, husks, straws, cobs and pressing cakes — have been gaining ground as a low-cost alternative, while turning by-products usually destined for burning or improper disposal into useful materials. The aim of this study was to systematise, through an integrative literature review, the knowledge published on the use of these materials in the removal of aquatic contaminants, with three articulated focuses: the physico-chemical mechanisms of biosorption, the fitting of classical kinetic and isothermal models, and the recent advances in chemical modifications and hybrid magnetic composites. The search was conducted in the Scopus, Web of Science, ScienceDirect and SciELO databases, covering 1990 to 2026, with descriptors combined in English and Portuguese, including biosorption, bioadsorption, biossorção and bioadsorção. After applying inclusion and exclusion criteria, the selected studies were read in full and organised in an extraction matrix containing biomass, target contaminant, pre-treatment, operating conditions, fitted models and modification strategies; analysis was qualitative, with thematic grouping around five axes. The findings converge on the predominance of the pseudo-second-order kinetic model and the Langmuir isotherm in the reported fittings, a pattern compatible with chemical adsorption on specific sites but which, in practice, coexists with ion exchange, surface complexation and electrostatic attraction. Alkaline, acidic and grafting-based modifications consistently increase adsorption capacity, while the incorporation of magnetic phases — especially magnetite — overcomes a classical operational bottleneck, by allowing rapid separation of the adsorbent from the liquid phase and broadening the viability of continuous-flow applications. Nevertheless, relevant gaps persist: insufficient experimental standardisation, scarcity of studies in real matrices and at pilot scale, and little attention to the toxicity of the material after multiple cycles. It is concluded that lignocellulosic biosorbents — especially the magnetic ones — represent a promising platform whose consolidation will depend mainly on studies in real effluents, the use of non-linear regression in modelling, ecotoxicological assessment of the material and the treated effluent, and tests in fixed-bed columns and at pilot scale.