Eco-environmental preparation of magnetic activated carbon modified with 3-aminopropyltrimethoxysilane (APTMS) from sawdust waste as a novel efficient adsorbent for humic acid removal: Characterisation, modelling, optimisation and equilibrium studies

The aim of the present study was to prepare the modified magnetic activated carbon from sawdust (AC/Fe3O4@SiO2-APTMS) as a novel adsorbent for efficient removal of humic acid (HA) from aqueous solutions. The adsorbent was characterised by BET, SEM, FTIR, VSM, and EDS analysis. The optimal values of independent variables were determined using Box-Behnken design based on the response surface methodology (RSM). The maximum HA adsorption of 97.85% was obtained at optimal conditions pH 3, the adsorbent dose 2 g/L, and the contact time 25 min. Analysis of the adsorption data by isothermal, kinetic, and thermodynamic models showed that the adsorption data followed the Langmuir isotherm (R2 = 0.9850) and the pseudo-second-order kinetic model (R2 = 0.9999). The adsorption process was spontaneous and endothermic. The adsorbent regeneration proved high HA removal efficiency after 4 adsorption cycles. The humic acid adsorption behaviour of the adsorbent supports its performance to remove organic contaminants from aqueous solutions.