The presence of organic pollutants in wastewater remains a prominent environmental concern due to the related ecological and health hazards. In response, this study employs an adsorptive methodology to address the removal of phenol and catechol, utilizing an organo-bentonite material modified with a pH-responsive switchable surfactant, dodecyldimethylamine oxide (C₁₂DAO). The synthesized organo-bentonite (C₁₂DAO-Bt) manifests commendable thermostability resulting from thermogravimetric analyses. The adsorption capacities of C₁₂DAO-Bt concerning phenol and catechol intensify with the augmentation of the C₁₂DAO/bentonite mass ratio. The utmost adsorption capacities of 150C₁₂DAO-Bt, deduced through a pseudo-second-order kinetic model, stand at 5.72 mg·g⁻¹ for phenol and 5.55 mg·g⁻¹ for catechol, respectively. Subject to modification by a pH-responsive surfactant, conditions leaning towards weakly acidic and neutral conditions (pH = 6~7) are conducive to the adsorption of phenolic compounds. Conversely, alkaline conditions (pH = 8~9) facilitate the dissociation of adsorbates from adsorbents. The augmentation of cationic strength within the examined scope incites the adsorption procedure while impeding the desorption efficacy. In the case of cationic species with comparable ionic strengths, Na⁺ exhibited a superior effect on the adsorption–desorption dynamics of phenol, while Ca²⁺ exerts a more pronounced effect on those of catechol. Moreover, even following five consecutive acid–base regulation cycles, C₁₂DAO-Bt retains a relatively high adsorption capacity and desorption efficacy, which underscores its exceptional regenerative capacity for removing phenolic compounds from wastewater.

Photochemical generation is an important pathway for atmospheric sulfate formation. However, the roles of atmospheric co-existing photosensitive dissolved organic matter (DOM) in sulfate formation are still unclear. The experimental results in this work provide evidence that atmospheric photosensitizers produce active intermediates to oxidize S(IV) into S(VI) under illumination. Quenching experiments of eight photosensitive model compounds (PS) demonstrate that their triplet-excited states (³PS*) dominate sulfate formation for the photosensitizing pathway with a contribution of over 90%, and ¹O₂ plays an important role in sulfate formation. The results using humic acid (HA) and water-soluble organic carbon in vehicle exhaust particles (WSOC) as representatives of atmospheric photosensitizers further verify that triplet-excited DOM (³DOM*) is the main reactive species for sulfate formation, which is consistent with the results of PS. Our findings provide new insights into the photochemical formation pathways of atmospheric sulfate.

A combined preparation of SO₂ and recovery of solid products was investigated as a hazard-free method to use coke as a reducer to treat electrolytic manganese residue (EMR) at high temperature. In this study, the response surface prediction and thermodynamic analysis of the high-temperature calcination of EMR were evaluated. In addition, the effects of mole ratio of EMR to coke and temperature on the gas–solid phase and the feasibility of calcined solid products as cement raw materials were also studied. The results showed that the release of sulfur from EMR mainly depends on the mole ratio of EMR to coke and temperature. The best condition for preparing SO₂ was EMR calcined for 60 min at 1000 °C and the molar ratio of C:CaSO₄ = 0.78:1. At this time, the volume fraction of SO₂ reached 7.6%, which meets the requirements for preparing sulfuric acid with SO₂. Under this condition, the sulfur in desulfurization manganese residue (DMR) was reduced to 0.38%, and DMR was used as cement raw material to prepare cement. The cement prepared by adding 10% DMR meets the national standard GB175. The method realized the recovery of sulfur in EMR and calcined solid products and promoted the resource utilization of EMR.