Synthetic dyes discharged into aquatic systems pose persistent environmental risks, requiring low-cost and sustainable treatment alternatives. This study clarifies the potential of Copernicia prunifera (carnauba) straw residues to produce biochars for methylene blue removal from aqueous media. Two bioadsorbents were prepared: a biochar derived from biomass retaining its natural wax layer (CSB) and another obtained from dewaxed biomass before pyrolysis (DCSB). Both biochars and their feedstocks were characterized through proximate and elemental analyses, PSD, FTIR, XRD, and SEM/EDS to elucidate key physicochemical differences. Dewaxing promoted the formation of a more condensed carbon matrix, reflected in lower O/C and (N+O)/C molar ratios, reduced surface oxidation, and a slightly more compact microstructure. These structural changes enhanced the adsorption performance of DCSB, which exhibited a Langmuir maximum capacity of 328.13 mg g–1, surpassing CSB. Equilibrium data were best fitted by the Langmuir model, suggesting monolayer adsorption on relatively homogeneous active sites, whereas adsorption kinetics followed a pseudo-second-order model. These results demonstrate that dewaxing carnauba leaf residues before carbonization improves the adsorptive efficiency of carnauba-derived biochars, highlighting their potential as effective and sustainable materials for dye removal from wastewater.
Silva et al. (Mon,) studied this question.
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