Degradation of p-chloroaniline by persulfate activated with ferrous sulfide ore particles

Compared with heavy metal catalysts, persulfate (PS) activated with iron-based materials for controlling refractory organic pollutants are more effective, environment-friendly, and safe to human health. However, Fe 2+ application is limited to acidic conditions, and Fe 0 is not thermodynamically stable in water. Ferrous sulfide (FeS) ore particles are large-sized, low-purity, crystallized iron-based materials that are inexpensive and readily available. In this work, FeS is proposed as an alternative electron donor to activate persulfate and degrade p -chloroaniline (PCA). The effects of initial solution pH, FeS dose, and persulfate concentration on PCA degradation and total organic carbon (TOC) removal were examined at 20   ±   5   °C in batch experiments. Cl − , SO 4 2 − , and Fe 3+ ions were the main inorganic products used to investigate the oxidative mechanism in the present system. Compared with Fe 2+ , FeS could serve as a continuous-releasing source of dissolved Fe 2+ and surface bound Fe 2+ , with PCA removal increasing by 80% at pH 7.0 for a 1   h reaction. In contrast with Fe 0 , recycling of Fe 3+ to Fe 2+ can prevent excessive Fe 2+ consumption and Fe 3+ accumulation. The PS activation mechanism was affected by the initial solution pH. And the application ranges of pH for PCA fast degradation was from 3.0 to 7.0 in the tested pH values of 3.0–11.0 and nearly complete degradation of PCA (>99%) was observed at 150   min, PCA degradation increased as the FeS dose and persulfate concentration increased. PCA removal, dechlorination, and TOC removal reached over 99% within 60, 210, and 500   min, respectively. Generation of small amounts of amorphous iron oxide precipitants on the residual FeS surface was, observed and FeS recyclability was conducted preliminarily. These findings suggest that FeS can function as an effective persulfate activator for PCA control.