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.

The degradation effect, degradation mechanism, oxidation kinetics, and degradation products of Atrazine (ATZ) by Ultrasound/Peroxymonosulfate (US/PMS) in phosphate buffer (PB) under different conditions were studied. It turned out that the degradation rate of US/PMS to ATZ was 45.85% when the temperature of the reaction system, concentration of PMS, concentration of ATZ, ultrasonic intensity, and reaction time were 20 °C, 200 μmol/L, 1.25 μmol/L, 0.88 W/mL, and 60 min, respectively. Mechanism analysis showed that PB alone had no degradation effect on ATZ while PMS alone had extremely weak degradation effect on ATZ. HO• and SO₄⁻• coexist in the US/PMS system, and the degradation of ATZ at pH7 is dominated by free radical degradation. Inorganic anion experiments revealed that Cl⁻, HCO₃⁻, and NO₃⁻ showed inhibitory effects on the degradation of ATZ by US/PMS, with Cl⁻ contributing the strongest inhibitory effect while NO₃⁻ showed the weakest suppression effect. According to the kinetic analysis, the degradation kinetics of ATZ by US/PMS was in line with the quasi-first-order reaction kinetics. ETA with concentration of 1 mmol/L reduced the degradation rate of ATZ by US/PMS to 10.91%. Product analysis indicated that the degradation of ATZ by US/PMS was mainly achieved by dealkylation, dichlorination, and hydroxylation, but the triazine ring was not degraded. A total of 10 kinds of ATZ degradation intermediates were found in this experiment.

To solve the water pollution problem caused by methylene blue (MB), areca residue biochar (ARB) was prepared by pyrolysis at 600 °C, and modified areca residue biochar (M-ARB) was obtained by modifying ARB with 1.5 mol/L NaOH, and they were utilized to adsorb and eliminate MB from water. The structural characteristics of ARB and M-ARB were examined, and the main influencing factors and adsorption mechanism of MB adsorption process were investigated. The outcomes demonstrated an increase in M-ARB’s specific surface area and total pore volume of 66.67% and 79.61%, respectively, compared with ARB, and the pore structure was more abundant, and the content of oxygen element was also significantly increased. When the reaction temperature was 25 °C, starting pH of the mixture was 10, the initial MB concentration was 50 mg/L, the ARB and M-ARB dosages were 0.07 g/L and 0.04 g/L, respectively, the adsorption equilibrium was achieved at about 210 min, and the elimination rate for MB exceeded 94%. The adsorption behaviors of ARB and M-ARB on MB were more in line with the Langmuir isotherm model (R² > 0.95) and the quasi-secondary kinetic model (R² > 0.97), which was characterized by single-molecule layer chemisorption. The highest amount of MB that may theoretically be absorbed by M-ARB in water ranging from 136.81 to 152.72 mg/g was 74.99–76.59% higher than that of ARB. The adsorption process was a spontaneous heat absorption reaction driven by entropy increase, and the adsorption mechanism mainly involved electrostatic gravitational force, pore filling, hydrogen bonding, and π–π bonding, which was a complex process containing multiple mechanisms of action. NaOH modification can make the ARB have more perfect surface properties and more functional group structures that can participate in the adsorption reaction, which can be used as an advantageous adsorption material for MB removal in water.

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.

Sheep manure was used to prepare biochar under pyrolysis temperature of 600ºC. The structural features of biochar were characterized by elemental analysis, BET analysis and scanning electron microscopy. The effects of pH, biochar dosage, adsorption time, temperature on adsorption of methyl orange (MO) in water by sheep manure biochar, as well as its adsorption mechanism, were investigated via batch experiments. The results showed that the sheep manure biochar had large specific surface area, abundant hole structure and high aromaticity and polarity. When temperature was 25ºC, MO concentration was 20 mg/L, initial pH was 4.0, and biochar dosage was 0.6 g/L, the adsorption achieved balance at about 250min, and the MO removal rate reached to 92.55%. Pseudo second-order kinetic model and Langmuir model could more accurately describe the adsorption behavior of MO onto sheep manure biochar, and the theoretical maximum adsorption capacity was 42.513 to 45.563 mg/g. Besides, the process is a favorable adsorption. Thermodynamic studies showed that the adsorption was a spontaneous, endothermic and entropy-increasing process. Sheep manure biochar could be used as a good adsorption material for MO in water, which achieved the goal of controlling waste by waste.

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%.