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.

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.

This paper aims to investigate the enhancement effect of tourmaline on anaerobic ammonium oxidation (ANAMMOX) process in two sequencing batch reactors (SBRs). SBR1 was operated in parallel with SBR2, but 2 g tourmaline was added to the reactor. The results showed that when the nitrogen loading rate (NLR) was gradually increased from 181.8 to $727.3\mathrm{mg}/(\mathrm{L}·\mathrm{d})$ , the nitrogen removal rate (NRR) of SBR2 decreased to $99.0\mathrm{mg}/(\mathrm{L}·\mathrm{d})$ from $576.7\mathrm{mg}/(\mathrm{L}·\mathrm{d})$ , corresponding to an increase of specific ANAMMOX activity (SAA) from 0.65 to $3.69\mathrm{mgN}/(\mathrm{gVSS}·\mathrm{h})$ .Tourmaline could control pH value to provide a stable environment for enrichment of ANAMMOX bacteria. Tourmaline promoted the growth and metabolism of ANAMMOX bacteria and enhanced the activity of the ANAMMOX reaction but was not a benefit for the granulation of ANAMMOX sludge. At the end of the start-up period, the 16S rRNA genes of ANAMMOX bacteria in SBR1 ($8.21\pm 0.07\times {10}^9\mathrm{copies}/\mathrm{mL}$ ) were two orders of magnitude higher than that in SBR2 ($5.13\pm 0.08\times {10}^7\mathrm{copies}/\mathrm{mL}$ ). The ANAMMOX sludge of SBR1 possessed a higher extracellular polymer substances (EPS) content than the SBR2 reactor ($194–287\mathrm{mg}/\mathrm{g}$ VSS in SBR1 and $203–252\mathrm{mg}/\mathrm{g}$ VSS in SBR2). The level of heme $c$ and TTC-dehydrogenase in SBR1 were still higher than that in SBR2.

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.

With the advancement of China’s agricultural modernization and scientific and technological progress, there has been a substantial increase in corn production, resulting in significant agricultural waste of materials such as corncobs. Conventional incineration methods fail to efficiently utilize the recyclable resources present in corncobs. In this investigation, corncob biochar film (CBC) was synthesized through the pyrolysis of corncob. Single-factor and orthogonal experiments were used to determine the conditions needed to prepare biochar film with the best Cr(VI) adsorption effect. The experiments showed that at a heating rate of 5 °C/min, pyrolysis temperature of 500 °C and pyrolysis time of 120 min, the Cr(VI) removal rate of prepared biochar film reached 73.55% and the adsorption capacity was 18.39 mg/g. Meanwhile, the factors affecting the removal of Cr(VI), including pH value, initial concentration of Cr(VI) solution, dosage of adsorbent, adsorption kinetics and isothermal adsorption, were analyzed in detail. The structures of CBC before and after Cr(VI) adsorption were analyzed by SEM, FTIR, XRD, XPS, and BET. These findings demonstrate the efficacy of corncob biochar film in Cr(VI) removal.