In recent years, wastewater containing heavy metal chromium has been discharged into water bodies. Metal chromium not only destroys the water environment but also poses a threat to human life and health. In order to solve the problem of chromium pollution more effectively, this study used corn straw as raw material to prepare biochar (MB) and used three methods: acid (HCl), alkali (NaOH) and metal salt (FeCl₃) to modify biochar (HMB, NaMB and FeMB) and investigated the strengthening effect of modified biochar on Cr(VI) adsorption. The morphology and surface chemical composition of biochar were studied by XRD, SEM, XPS, FITR and other characterization methods. It was found that the modification of HCl, NaOH and FeCl₃ improved the physical and chemical properties of MB (such as crystal structure, specific surface area, pore size and surface composite film), thus promoting the adsorption of Cr(VI). At the same time, an adsorption single-factor experiment, adsorption kinetics experiment, isothermal adsorption experiment and cyclic regeneration experiment were carried out on the four adsorbents. The effects of biochar on Cr(VI) adsorption performance under different pH, Cr(VI) initial concentration, biochar dosage and time were compared, and the adsorption mechanism of four adsorbents on Cr(VI) in aqueous solution was studied. It was found that the FeCl₃-modified biochar provided more adsorption sites for chromium ions due to the successful loading of Fe, Fe³⁺ and iron oxide particles onto the MB surface to form a composite film, and the Fe-O groups introduced by the composite film formed a coordinated adsorption with dichromate ions. At 25 °C and pH = 2, FeMB reached saturation at 1440 min, the maximum adsorption capacity was 23.4 mg/g and its removal rate of Cr(VI) remained above 45% after five cycles. The adsorption of Cr(VI) was significantly enhanced.

Highly ordered TiO₂ nanotube arrays (NTs) have been widely used for photocatalysis application. In this study, to further improve the photocatalysis activity of TiO₂ NTs, Cu/TiO₂ NTs were prepared through an anodic oxidation and impregnation–reduction method. The morphology and crystalline phase of the pure TiO₂ NTs and Cu/TiO₂ NTs were characterized by SEM and X-ray diffraction. The photocatalytic performance of Cu/TiO₂ NTs was evaluated by photocatalytic reduction of Cr(VI) under UV light. The rate constant of photocatalytic reduction of Cr(VI) on Cu_0.01/TiO₂ NTs which had the optimal Cu loading content was 9.5 times higher than that on unmodified TiO₂ NTs. And the experiment results of different initial concentration of Cr(VI) and pH demonstrated that they greatly influenced the removal efficiency of Cr(VI). The photoelectric properties of TiO₂ NTs with Cu particle loading were investigated by photoelectrochemical characterization, including photocurrent response, open-circuit voltage, electro-chemical impedance spectroscopy Nynquist plots, and Mott–Schottky plots. The enhancement of the photocatalytic performance of Cu/TiO₂ NTs indicated that the electrons could transfer faster and be utilized more easily due to the formation of Schottky barrier on the interface of Cu and TiO₂. The detailed electrons transfer mechanism of Cu/TiO₂ NTs was proposed.

This study focuses on synthesizing a composite material of Ag/ZnO/BiOCl using Ag, ZnO, and BiOCl as raw materials. The material was prepared by loading Ag and BiOCl onto ZnO nanofilms, aiming to enhance the photocatalytic degradation of ciprofloxacin (CIP). Optimization of the photocatalytic degradation process through single-factor experiments revealed that under conditions of an initial CIP pH of 9, an Ag/ZnO/BiOCl dosage of 1 g/L, and an initial CIP concentration of 5 mg/L the conversion efficiency of CIP reached 98.79% after 150 min of exposure to a 250 W xenon lamp simulating sunlight. Furthermore, the composite material maintained a conversion efficiency of 86.17% for CIP even after five cycles of reuse, demonstrating its excellent stability. The optical properties, elemental composition, valence state, crystallinity, and morphology of the samples were analyzed using techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), UV–visible diffuse reflectance spectroscopy (UV-vis DRS), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results indicate that the introduction of Ag expanded the light response range of ZnO, while the addition of BiOCl improved the separation efficiency of electron–hole pairs in the composite nanomaterial. The photocatalytic mechanism was further elucidated through radical scavenging experiments, confirming that ·OH and h⁺ are the main active species in the degradation process.

Microbial fuel cells (MFCs) have exhibited potential in energy recovery from waste. In this study, an MFC reactor with a polyaniline–sodium alginate–graphene oxide (PANI–SA–GO)/carbon brush (CB) hydrogel anode achieved maximum power density with 4970 mW/m³ and produced a corresponding current density of 4.66 A/m², which was 2.72 times larger than the MFC equipped with a carbon felt film (CF) anode (1825 mW/m³). Scanning electron microscopy indicated that the PANI-SA-GO/CB composite anode had a three-dimensional macroporous structure. This structure had a large specific surface area, providing more sites for microbial growth and attachment. When the charging-discharging time was set from 60 min to 90 min, the stored charge of the PANI-SA-GO/CB hydrogel anode (6378.41 C/m²) was 15.08 times higher than that of the CF (423.05 C/m²). Thus, the mismatch between power supply and electricity consumption was addressed. This study provided a simple and environment-friendly modification method and allowed the prepared PANI–SA–GO/CB hydrogel anode to markedly promote the energy storage and output performance of the MFC.

Potato starch wastewater, a byproduct of potato processing, is an escalating environmental concern due to its high concentrations of COD (chemical oxygen demand), ammonia nitrogen, and total phosphorus (TP). Addressing this challenge, this research introduced a novel method combining chitosan-modified biochar film (CBC) adsorption with subsequent ultrafiltration. SEM (scanning electron microscope), FTIR (Fourier transform infrared spectral), XRD (X-ray diffractometer), and BET (specific surface area) analyses validated CBC’s enhanced surface characteristics, confirming successful chitosan (CS) film impregnation. CBC exhibited superior adsorption capacities, especially 40%wt-CBC, optimizing COD removal at 79.8%, ammonia nitrogen at 93.3%, and TP at 91.2%. Kinetic studies associated the adsorption process with a pseudo-second-order model, highlighting chemical adsorption. Additionally, the Langmuir isotherm model suggested monolayer adsorption with no inter-adsorbate interactions. The treated effluent, post adsorption, was directed through an ultrafiltration membrane, ensuring water quality suitable for reuse. This integrative treatment not only offers an effective solution for potato starch wastewater management but also underscores the potential for sustainable water resource recovery in the food processing sector.

Herein, a chitosan film (CS) was modified using 2,3-epoxy-propyl trimethyl ammonium chloride (GTA) to flocculate granular pollutants in potato starch wastewater, aiming at the deficiencies of poor water solubility and weak electropositivity of the chitosan film. By examining the degree of substitution of chitosan film amino under different factors and different levels and response surface optimization tests, the optimum preparation conditions of chitosan film quaternary ammonium salt (HTCC) were obtained. Using scanning electron microscopy (SEM), Fourier infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and ¹H-nuclear magnetic spectroscopy, the nucleophilic substitution reaction of the GTA molecule with the hydrogen atoms in the chitosan film amino group successfully improved the water solubility and electropositivity of the chitosan film. HTCC was used to treat potato starch wastewater, and the optimal flocculation conditions were obtained. The flocculation product was recovered, and the composition analysis of the flocculation product demonstrated that HTCC-potato protein flocculation precipitate was rich in high protein, which is a good choice of feed and can realize sustainable utilization of resources.