Advanced adsorptive removal of dimethyl phthalate from water using a tertiary amine-functionalized polymeric resin: insights into experimental design and statistical analysis

This study investigates the effective removal of dimethyl phthalate (DMP) from aqueous solutions using Purolite Macronet MN100, a polymer-based adsorbent containing tertiary amine functional groups. A series of batch experiments was performed to assess the influence of resin dosage and solution pH, while adsorption kinetics were analyzed to determine the optimal contact time and the underlying rate-limiting mechanism. Equilibrium data were interpreted using adsorption isotherm models, and thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were calculated to evaluate the feasibility and spontaneity of the process. Additionally, the effect of common coexisting ions in wastewater (Na⁺, K⁺, Mn²⁺, Ca²⁺, Mg²⁺) on DMP removal was examined. The optimum removal efficiency (>97%) was achieved using 0.02 g of resin per 25 mL solution at pH 2–6, with equilibrium established within 300 minutes. The adsorption behavior was best described by the Langmuir isotherm, indicating monolayer adsorption with a maximum capacity of 463.37 mg g⁻¹. Mechanistic evaluation revealed that π–π interactions and hydrogen bonding were the dominant forces driving DMP adsorption. The presence of competing cations had minimal impact, demonstrating the adsorbent's strong selectivity toward DMP. Desorption studies showed complete DMP recovery using absolute ethanol (>99%), with >99% regeneration efficiency. Optimization using Central Composite Design (CCD) under Response Surface Methodology (RSM) produced a statistically robust model (R² = 0.98), consistent with the experimental results. Overall, Purolite MN100 proved to be a highly efficient, selective, and regenerable adsorbent suitable for DMP removal in wastewater treatment processes.