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In this study, bagasse was used as a carbon source to prepare magnetic porous biochar (MBC) through the method of high-temperature pyrolysis with K2FeO4 as the oxidation promoter. Different from the other two-step methods for preparing magnetic biochar, magnetic loading and graphitization can be realized in one step in this method at a high temperature with K2FeO4 as an activator. Through the characterization analyses of XRD, Raman, FT-IR, BET, VSM, and other methods, the modified MBC is proven to have a high degree of graphitization with a large specific surface area of 846.69 m2/g and a high saturation magnetization of 22.51 emu/g. As the adsorption process fitted with the Langmuir model, the maximum adsorption capacities of MBC-800 on the tetracycline (TC) and ciprofloxacin (CIP) were calculated to be 416.67 mg/g and 434.78 mg/g, respectively. The adsorption mechanism of MBC-800 for the adsorption of TC (or CIP) mainly includes π-π conjugation, pore filling, hydrogen bonding with oxygen-containing functional groups, and chemical adsorption including ion exchange and electrostatic attraction. MBC can maintain high adsorption capacity for TC (or CIP) after multiple cycles. The study is expected to provide a possibility for the preparation of magnetic biochar and extend our knowledge of its application in antibiotic wastewater treatment. [ABSTRACT FROM AUTHOR]

Biochar with abundant functional groups, porous structure, and high specific surface area has been widely used as an adsorbent for the removal of metal ions, and its low production costs make it economically suitable for large-scale application in various industries. Hydroxyapatite nanoparticles were used to functionalize magnetic rice husk biochar (MBC) to produce hydroxyapatite functionalized magnetic rice husk biochar (HAP@MBC) in this study. The functional groups, magnetism performance, surface morphology, and aperture structure of HAP@MBC were characterized to explore the feasibility of its application in the treatment of wastewater containing Cu(II) ions. It is found that the maximum adsorption removal rate reaches 96.02% at 35°C, pH=5.0 , with an adsorbent dosage of 0.65 g/L and an initial Cu(II) ion concentration of 50 mg/L. Additionally, adsorption kinetics, isotherms, and thermodynamics were analyzed to probe into the adsorption mechanism of Cu(II) ions by HAP@MBC. The results show that the adsorption process is very close to the pseudo-second-order model, indicating that the adsorption process is mainly controlled by chemisorption. The adsorption of Cu(II) ions can also be fitted by the intraparticle diffusion model, revealing that the adsorption rate is limited by intraparticle diffusion as well as other factors. Moreover, the adsorption process is consistent with the Langmuir isotherm, and the saturated adsorption capacity is calculated to be 81.59 mg/g. Thermodynamic analysis shows that the value of adsorption enthalpy change is 48.35 kJ/mol , suggesting the adsorption process is chemisorption. More precisely, it is a spontaneous entropy-increasing reaction, and an increase in the temperature is conducive to the adsorption. To sum up, HAP@MBC exhibits perfect adsorption properties and has the potential to be a novel and promising adsorbent for the removal of Cu(II) ions. [ABSTRACT FROM AUTHOR]

In this study, the siphon-type composite vertical flow constructed wetland (Sc-VSsFCW) was constructed with anthracite and shale ceramsite chosen as the substrate bed materials. During the 90-day experiment, typical pollutant removal effects of wastewater and extracellular polymeric substance (EPS) accumulation were investigated. Meanwhile, X-ray diffraction and scanning electron microscopy were used to examine the phase composition and surface morphology to analyze adsorptive property. Additionally, we evaluated the impact of siphon effluent on clogging and depolymerization by measuring the EPS components' evolution within the system. The findings reveal that both the anthracite and shale ceramsite systems exhibit impressive removal efficiencies for total phosphorus (TP), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP), chemical oxygen demand (COD), ammonium nitrogen (NH 4 + -N), and nitrate nitrogen (NO 3 - -N). However, as the experiment progressed, TP removal rates in both systems gradually declined because of the saturation of adsorption sites on the substrate surfaces. Although the dissolved oxygen (DO) levels remained relatively stable throughout the experiment, pH exhibited distinct patterns, suggesting that the anthracite system relies primarily on chemical adsorption, whereas the shale ceramsite system predominantly utilizes physical adsorption. After an initial period of fluctuation, the permeability coefficient and porosity of the system gradually stabilized, and the protein and polysaccharide contents in both systems exhibited a downward trend. The study underscores that anthracite and shale ceramsite have good effectiveness in pollutant removal as substrate materials. Overall, the hydraulic conditions of the double repeated oxygen coupling siphon in the Sc-VSsFCW system contribute to enhanced re-oxygenation capacity and permeability coefficient during operation. The changes in EPS content indicate that the siphon effluent exerts a certain depolymerization effect on the EPS within the system, thereby mitigating the risk of biological clogging to a certain extent. PRACTITIONER POINTS: The system can still maintain good pollutant treatment effect in long-term operation. The re-oxygenation method of the system can achieve efficient and long-term re-oxygenation effect. The siphon effluent has a certain improvement effect on the permeability coefficient and porosity, but it cannot effectively inhibit the occurrence of clogging. The EPS content did not change significantly during the operation of the system, and there was a risk of biological clogging., (© 2024 Water Environment Federation.)