Multistage utilization of soybean straw-derived P-doped biochar for aquatic pollutant removal and biofuel usage

The preparation of starch-based green adsorption gel with tunable water channels through extrusion-dual cross-linking method

In addressing the challenges of recovery and microparticle residue associated with biochar, loading biochar with starch presents a viable solution. However, starch's high hydrophilicity and viscosity introduce water resistance and uniform loading issues. This study proposes an innovative ionically synergistic dual crosslinking modification method, utilizing an extruder barrel as a novel reactor. This method enables the construction of highly water-resistant starch gels and the uniform and robust loading of biochar micro-nanoparticles within the gel matrix, achieving the "one-step" preparation of starch-biochar-based adsorptive gels. The starch-biochar-based adsorptive gel (Bc-S-D) exhibits excellent removal efficiency for the hazardous waste methylene blue (MB) with a qe value of 549.45 mg/g. This removal efficiency is maintained at 85.37 ± 0.08 % even after five cycles. The textural results indicate that Bc-S-D maintains a high recovery performance of 91.51 % after prolonged water immersion. Scanning Electron Microscopy (SEM) reveals that it has the lowest porosity (47 ± 3.36 %) and micropore size (16.53 ± 2.71 μm). Furthermore, the specific surface area was determined using the Brunauer-Emmett-Teller (BET) model, which is 7.46 ± 0.03 m2/g, representing a 448.53 % increase compared to the unmodified state. A quasi-primary kinetic model for the adsorption of MB on the adsorbent follows the Langmuir model. The starch-biochar-based adsorption gel is also appropriate for high-temperature dyeing wastewater adsorption situations because of its superior water resistance, structural recoverability, and high-temperature stability, which allow rapid, residue-free separation and recovery. This research provides a new reaction method for preparing modification biological macromolecules and loading new biological macromolecule functional materials to achieve the full-cycle green treatment of dyeing wastewater.

High-efficient removal of tebuconazole from aqueous solutions using P-doped corn straw biochar: Performance, mechanism and application

Due to the serious threat posed by tebuconazole to the aquatic ecosystem, it is imperative to develop a highly efficient adsorbent material for the sustainable remediation of tebuconazole-contaminated water. Herein, a phosphorus (P)-doped biochar from corn straw and H3PO4 was fabricated by one-step pyrolysis for tebuconazole adsorption. Results showed that the P-doped biochar produced at 500℃ (PBC500) possesses a large specific surface area (SSA=869.6 m2/g), abundant surface functional groups, and the highest tebuconazole adsorption capacity (429.6 mg/g). The adsorption of tebuconazole on PBC500 followed pseudo-second-order kinetics and Langmuir adsorption isotherm models. Thermodynamic calculations indicated that the adsorption of tebuconazole by PBC500 was a spontaneous, endothermic process with a random increase. Adsorption mechanism mainly involves pore filling, π-π interactions, hydrogen bonding, and hydrophobic interaction. Moreover, PBC500 demonstrated robust anti-interference capabilities in adsorbing tebuconazole from diverse water sources and exhibited excellent reusability, underscoring its potential for a broad array of practical applications.

Sustainable efficient utilization of magnetic porous biochar for adsorption of orange G and tetracycline: Inherent roles of adsorption and mechanisms

Iron-doped biochar has been widely used as an adsorbent to remove contaminants due to the high adsorption performance, but it still suffers from complicated preparation methods, unstable iron loading, unsatisfactory specific surface area, and uneven distribution of active sites. Here, a novel magnetic porous biochar (FeCS800) with nanostructure on surface was synthesized by one-pot pyrolysis method of corn straw with K2FeO4, and used in orange G (OG) and tetracycline (TC) adsorption. FeCS800 exhibited outstanding adsorption capacities for OG and TC after K2FeO4 activation and the adsorption data were fitted satisfactorily to Langmuir isotherm and Pseudo-second-order kinetic model. The maximum adsorption capacities of FeCS800 for OG and TC were around 303.03 mg/g and 322.58 mg/g, respectively, at 25 °C and pH 7.0, which were 16.27 and 24.61 times higher than that before modification. Thermodynamic studies showed that the adsorption of OG/TC by FeCS800 were thermodynamically favorable and highly spontaneous. And the adsorption capacity of OG and TC by FeCS800 remained 77% and 81% after 5 cycles, respectively, indicating that FeCS800 had good stability. The outstanding adsorption properties and remarkable reusability of FeCS800 show its great potential to be an economic and environmental adsorbent in contaminants removal.

Novel cow dung-doped sludge biochar as an efficient ozone catalyst: Synergy between graphitic structure and defects induces free radical pathways

A composite material, cow dung-doped sludge biochar (Zn@SBC-CD), was synthesized by one-step pyrolysis using ZnCl2 as an activating agent and applied to a catalytic ozonation process (COP) for methylene blue (MB) removal. SEM, XRD, FTIR, XPS and BET analyses were performed to characterize the biochar (BC) catalysts. Zn@SBC-CD had high graphitization degree, abundant active sites and uniform distribution of Zn on its surface. Complete removal of MB was achieved within 10 min, with a removal rate much higher than that of ozone alone (32.4%), implying the excellent ozone activation performance of Zn@SBC-CD. The influence of experimental parameters on MB removal efficiency was examined. Under the optimum conditions in terms of ozone dose 0.04 mg/mL, catalyst dose 400 mg/L and pH 6.0, COD was completely removed after 20 min. Electron paramagnetic resonance (EPR) analysis revealed radical and non-radical pathways were involved in MB degradation. The Zn@SBC-CD/O3 system generated superoxide anion radicals (•O2-), which were the main active species for MB removal, through adsorption, transformation, and transfer, Furthermore, Zn@SBC-CD exhibited good reusability and stability in cycling experiments. This study provides a novel approach for the utilization of cow dung and sludge in synthesis of functional biocatalysts and application in organic wastewater treatment.

The application of P-modified biochar in wastewater remediation: A state-of-the-art review

Phosphorus modified biochar (P-BC) is an effective adsorbent for wastewater remediation, which has attracted widespread attention due to its low cost, vast source, unique surface structure, and abundant functional groups. However, there is currently no comprehensive analysis and review of P-BC in wastewater remediation. In this study, a detailed introduction is given to the synthesis method of P-BC, as well as the effects of pyrolysis temperature and residence time on physical and chemical properties and adsorption performance of the material. Meanwhile, a comprehensive investigation and evaluation were conducted on the different biomass types and phosphorus sources used to synthesize P-BC. This article also systematically compared the adsorption efficiency differences between P-BC and raw biochar, and summarized the adsorption mechanism of P-BC in removing pollutants from wastewater. In addition, the effects of P-BC composite with other materials (element co-doping, polysaccharide stabilizers, microbial loading, etc.) on physical and chemical properties and pollutant adsorption capacity of the materials were investigated. Some emerging applications of P-BC were also introduced, including supercapacitors, CO2 adsorbents, carbon sequestration, soil heavy metal remediation, and soil fertility improvement. Finally, some valuable suggestions and prospects were proposed for the future research direction of P-BC to achieve the goal of multiple utilization.