Optimized Adsorption of Dyes and Antibiotics onto Natural Acacia Ataxacantha for Water Treatment

This study explores the potential ofAcacia Ataxacantha(Acacia) biomass as a low-cost and effective biosorbent for removing methylene blue dye (MB) and ciprofloxacin antibiotic (CIP) from water. The biosorbent was thoroughly characterized using FTIR, BET, SEM-EDX, XRD, and TGA-DTG, confirming the presence of key functional groups (−OH, −COOH). Optimal removal was achieved at room temperature, pH 7, and a biomass dosage of 2 g/L, with short equilibrium times of 30 min for MB and 5 min for CIP─faster than many conventional adsorbents. Isotherm analysis revealed that MB adsorption followed the Temkin model, whereas CIP conformed to the Langmuir model. The latter model showed maximum adsorption capacities of 133 mg/g for MB and 171 mg/g for CIP, which are comparable to or better than those of other biosorbents. The surface coverage at 25 °C was 36% for MB and 32% for CIP, indicating partial site utilization. Kinetic studies indicated that the adsorption process fits a pseudo-second-order model. Activation energy calculations yielded 34.5 kJ/mol for MB and −23.0 kJ/mol for CIP, indicating distinct adsorption mechanisms. Thermodynamic analysis confirmed that both adsorption processes were exothermic and spontaneous at 25 °C, with MB showing stronger interaction energy than CIP. A basic cost analysis estimated the production cost of 1 kg of Acacia biosorbent at 1.54 USD. Regeneration tests showed good reusability for up to four cycles for both MB and CIP. These results suggest that Acacia is a cost-effective and sustainable biosorbent for removing MB and CIP from water, offering a practical alternative to energy-intensive treatment methods.