Enhanced adsorptive removal of malachite green dye from aqueous solution using raw and acid modified rosemary biomass

Water contamination resulting from waste systems owing to industrial expansion and escalating human activities has emerged as a significant global environmental issue. Agricultural waste biomass is extensively utilized as a bioadsorbent for the removal of harmful contaminants. This study emphasizes the production of an economical, zero-waste adsorbent derived from rosemary biomass and illustrates how sulfuric acid modification significantly transforms its surface characteristics, resulting in a marked increase in malachite green adsorption capacity. The synthesized bioadsorbent was analyzed utilizing FT-IR, SEM, XRD, zeta potential, and pH pzc . Experimental investigations were performed to examine the effect of process variables, such as contact time (0–180 min), initial dye concentration (100–500 mg/L), pH (2–10), and biomass dosage (0.01–0.20 g/50 mL), on dye removal efficacy. The effect of salt solutions on the adsorption process was examined, revealing that electrostatic interactions significantly contributed to the adsorption mechanism. The modeling investigation demonstrates that the Langmuir and pseudo-second order models exhibit strong concordance (R 2 = 0.9999) with isotherm and kinetics, respectively. The intraparticle diffusion kinetic model indicated that the adsorption process may transpire through many processes. The monolayer adsorption capacities of raw and sulfuric acid-treated biomass had peak values of 247.5 and 497.4 mg/g at 298 K, respectively. Thermodynamic results have shown that both raw ( \(\:{\varDelta\:H}_{A}^{o}=9.930\) kJ/mol and \(\:{\varDelta\:G}_{A}^{o}=-22.61\) kJ/mol) and modified rosemary ( \(\:{\varDelta\:H}_{A}^{o}=44.97\) kJ/mol and \(\:{\varDelta\:G}_{A}^{o}=-23.54\) kJ/mol) biomass are endothermic and spontaneous. Consequently, it was determined that sulfuric acid-modified rosemary biosorbent possesses superior efficacy for dye removal in remediation operations.