Benzene dye intermediates (BDI) wastewater has caused major environmental concern due to its potential carcinogenic, teratogenic, and mutagenic effects. Treatability reports dealing with the advanced chemical oxidation of BDI are limited. In this work, the Fenton method was applied to treat the real BDI wastewater to provide a deep insight into single as well as combinative effects of the main process variables influencing the treatment performance. First, we evaluated the effects of the reaction time, initial pH, initial [H₂O₂] concentration, and initial [Fe²⁺] concentration on the Fenton oxidation efficiency of real BDI wastewater. Furthermore, based on the Box–Behnken response surface methodology (RSM), an empirical mathematical model between response values, namely the chemical oxygen demand (COD), total organic carbon (TOC), color removal efficiency, sludge iron mass ration (SIMR), and influence factors were established to evaluate the interaction effects and optimize the experimental conditions. All of the proposed models were adequate with an R² range from 0.9561 to 0.9880. In addition, three of these factors had different effects on four studied response values. By overlaying the responses, the optimum conditions were obtained at an initial pH of 4.13, an initial [H₂O₂] concentration of 1.0 M, and an initial [Fe²⁺] concentration of 0.36 M. Verification experiments were conducted at the optimum conditions, which led to a COD removal efficiency of 85.29%, a TOC removal efficiency of 75.23%, a color removal efficiency of 99.99%, and a SIMR response of 0.39, respectively, and the results were in good agreement with the values predicted by the model. In addition, the BOD₅/COD ratio was observed to increase from 0.08 to 0.49, indicating an improvement in biodegradability.

Phthalic acid esters (PAEs) are often detected in remediated groundwater using appropriate oxidant materials by in situ groundwater treatment. The study compares zero-valent iron–persulfate with a pyrite–persulfate system to degrade three PAEs—di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), and dimethyl phthalate (DMP). Column experiments were conducted, and rapid oxidation occurred in a pyrite–persulfate system due to sulfate radical generation. DMP concentration was found at about 60.0% and 53.0% with zero-valent iron (ZVI) and pyrite activation of persulfate, respectively. DBP concentration was measured as 25.0–17.2% and 23.2–16.0% using ZVI–persulfate and pyrite–persulfate systems, respectively. However, DEHP was not detected. The total organic carbon concentration lagged behind the Ʃ₃ PAEs. Persulfate consumption with ZVI activation was half of the consumption with pyrite activation. Both systems showed a steady release of iron ions. Overall, the oxidation–reduction potential was higher with pyrite activation. The surface morphologies of ZVI and pyrite were investigated using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and XPS. Intensive corrosion occurs on the pyrite surface, whereas the ZVI surface is covered by a netting of iron oxides. The pyrite surface showed more oxidation and less passivation in comparison with ZVI, which results in more availability of ${\mathrm{Fe}}^{2+}$ for persulfate activation. The pyrite–persulfate system is relatively preferred for rapid PAE degradation for contamination.