To solve the double problems of methylene blue (MB) pollution in water and waste of straw resources, rape straw biochar (RSB₆₀₀) was made by thermal decomposition of discarded rape residues at 600 °C, and modified RSB600(M-RSB₆₀₀) was prepared after treatment with NaOH for MB adsorption. The physicochemical properties, MB adsorption properties and mechanism of RSB600 and M-RSB600 were studied. According to the experimental findings, M-RSB₆₀₀ has stronger aromaticity, higher hydrophilicity, and more polarity than RSB₆₀₀. Under the same adsorption conditions, M-RSB600 obtained better MB adsorption effect with less dosage. The MB equilibrium adsorption capacity of M-RSB600 reached 268.46 mg/g, which was 65.6% higher than that of RSB600. The quasi-second-order kinetic model better described the adsorption kinetics of MB on RSB₆₀₀ and M-RSB₆₀₀ (R² > 0.98), and the Freundlich and Temkin models better described the adsorption isotherms (R² > 0.95). The adsorption process was spontaneous, internal heat and entropy driven multilayer adsorption, dominated by chemical adsorption, specifically involving multiple interaction mechanisms, including electrostatic adherence, hydrogen-bond, π-π bond and ion-exchange. The results demonstrated that NaOH modification obviously improved the structure of RSB and make it had better adsorption and regeneration performance. M-RSB600 can be utilized as the ideal substance for effectively removing MB from effluent.

Biochar was prepared by pyrolyzing goat manure at 600ºC (GMB600) and used as an adsorbent for the removal of Rhodamine B (RhB) from aqueous solution. The structure and properties of GMB600 were characterized by elemental analysis, BET, SEM and FTIR. The effects of solution pH, biochar dosage, contact time, initial RhB concentration and temperature on the adsorption behaviors were investigated by batch experiments, which were further used to preliminarily discuss the adsorption mechanism. Results showed that the adsorption equilibrium could attain in 150 min and the RhB removal rate could reach 96.5% under the conditions of solution pH 5.0, GMB600 dosage of 0.4 g/L, initial RhB concentration of 20 mg/L and temperature of 25ºC. The adsorption behavior of RhB onto GMB600 followed the pseudo second-order kinetic model, and the adsorption isotherm was better fitted with the Freundlich model. Thermodynamic parameters such as Gibbs free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) indicated that the adsorption of RhB onto GMB600 was a spontaneous and endothermic process with increased entropy. FTIR analysis showed that the oxygen-containing functional groups on GMB600 provided RhB with abundant adsorption sites, and the adsorption mechanism was possibly attributable to the hydrogen bond and π-π interactions between RhB and GMB600.

The degradation effect of heat/peroxymonosulfate (PMS) on atrazine (ATZ) is studied. The results show that the heat/PMS degradation for ATZ is 96.28% at the moment that the phosphate buffer (PB) pH, temperature, PMS dosage, ATZ concentration, and reaction time are 7, 50 °C, 400 μmol/L, 2.5 μmol/L, and 60 min. A more alkaline PB is more likely to promote the breakdown of ATZ through heat/PMS, while the PB alone has a more acidic effect on the PMS than the partially alkaline solution. $\mathrm{HO}•$ and $\mathrm{S}{\mathrm{O}}_4^{-}•$ coexisted within the heat/PMS scheme, and ATZ quantity degraded by $\mathrm{HO}•$ and $\mathrm{S}{\mathrm{O}}_4^{-}•$ in PB with pH = 7, pH = 1.7~1. $\mathrm{HC}{\mathrm{O}}_3^{-}$ makes it difficult for heat/PMS to degrade ATZ according to inorganic anion studies, while $\mathrm{C}{\mathrm{l}}^{-}$ and $\mathrm{N}{\mathrm{O}}_3^{-}$ accelerate the degradation and the acceleration effect of $\mathrm{N}{\mathrm{O}}_3^{-}$ is more obvious. The kinetics of ATZ degradation via heat/PMS is quasi-first-order. Ethanol (ETA) with the identical concentration inhibited ATZ degradation slightly more than $\mathrm{HC}{\mathrm{O}}_3^{-}$, and both of them reduced the degradation rates of heat/PMS to 7.06% and 11.56%. The addition of $\mathrm{C}{\mathrm{l}}^{-}$ and $\mathrm{N}{\mathrm{O}}_3^{-}$ increased the maximum rate of ATZ degradation by heat/PMS by 62.94% and 189.31%.

Using rabbit manure as raw material, three distinct types of rabbit manure biochar (RBC400, RBC500, and RBC600) were prepared via pyrolysis at 400 °C, 500 °C, and 600 °C, respectively. The effects of pyrolysis temperature on the physicochemical properties of biochar were examined by scanning electron microscopy, Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction techniques. Rabbit manure biochar was used to activate permonosulfate (PMS) to degrade rhodamine B (RhB). The findings revealed that RBC600 prepared at 600 °C showed the strongest catalytic activity due to its abundant pores and pore structure, high graphitization, and high carbonization degree. Under optimal reaction conditions (0.4 g/L PMS and 0.6 g/L RBC600), the degradation rate of 50 mg/L RhB reached 93.38% within 60 min. RBC600 can be effectively recovered, and effective catalytic activity can be sustained after five cycles. The quenching and EPR experiments showed that both free-radical (SO₄⁻ and ·OH) and non-free-radical (¹O₂) pathways contributed to the degradation of RhB, in which ¹O₂ performed a dominant role. In conclusion, the new PMS activator prepared in this study not only realizes the “waste to waste” use of manure waste but also provides technical support for the efficient resource-based treatment of organic wastewater.

In phosphate buffer, the degradation of ATZ by ozone/(O₃/H₂O₂) under various circumstance was explored and the degradation mechanism and dynamics were probed. The findings revealed that when maintaining the reaction temperature at 25 °C, the H₂O₂ concentration and the O₃ concentration were 20 mol/L and 20 mol/L, respectively. Moreover, the degradation rate of 5 mol/L ATZ under the influence of O₃/H₂O₂ was 92.59% in phosphate buffer at pH7. The mechanism analysis showed that HO• and O₃ underwent co-oxidized degradation and that the HO• and O₃ oxidation degradation ratios were close to 1:1 under acidic conditions. Furthermore, HO• oxidative degradation dominated the ATZ degradation process. The kinetics analysis showed that the ATZ kinetics of O₃/H₂O₂ degradation were more compatible with quasi-second-order reaction kinetics under different temperatures, pH values, and H₂O₂ concentrations.

Experimental and theoretical studies have been conducted to investigate the adsorption of atrazine in aqueous solutions by sheep manure-derived biochar synthesized at 650°C (SMB650). The results of characterization analysis showed that SMB650 possessed large specific surface area and was rich in pore structure and functional groups. The removal efficiency of atrazine by SMB650 was 95.3% under the optimum conditions, of which contact time, initial atrzaine concentration, initial solution pH, SMB650 dosage and temperature were 150 min, 1500 μg/L, 3.0, 1.6 g/L and 25ºC, respectively. The results of kinetic and isotherm studies revealed that the pseudo second-order and the Freundlich model fit the experimental data best (R2>0.98). The adsorption of atrazine onto SMB650 belonged to multi-molecular layer adsorption. The calculated thermodynamic parameters like free energy change (ΔGθ), enthalpy change (ΔHθ) and entropy change (ΔSθ) were -7.8730 to -6.2976 kJ/mol, 17.2179 kJ/mol and 0.0788 kJ/(mol·K), respectively, indicating that the adsorption process of atrazine onto SMB650 was spontaneous, endothermic and entropy-increased. The present study showed that the sheep manure-derived biochar could be used as a promising adsorbent for the removal of atrazine from aqueous solutions. Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University