Elaborating the mechanism of lead adsorption by biochar: Considering the impacts of water-washing and freeze-drying in preparing biochar

In-situ structural modification on spinel oxide to achieve efficient removal of refractory organics: Triple optimisation of degradation performance

Spinel oxide has attracted interest in wastewater treatment, owing to its visible light (VIS) adsorption properties and bimetallic synergism. However, owing to the inefficient separation of photogenerated carriers and poor redox property, there is an urgent need to develop appropriate modification strategies to address these bottlenecks. This study aimed to develop CuFe2O4/CuFeSx (CFO/CFSx) heterojunction with oxygen vacancies (OVs) via an in-situ structural modification to trigger the generation of more radicals with low oxidant consumption for the efficient degradation of refractory organics. This customized heterojunction improved the light-trapping ability and photoelectrons utilisation, promoting the reduction of metal valence by photoelectrons to enhance the activation of peroxymonosulfate (PMS). Meanwhile, OVs also provided more active sites to activate PMS to generate superoxide radicals (O2-), which were further converted to hydroxyl radicals (OH) to ensure considerable oxidation capability. Notably, Sulfur-mediated metal valence reduction boosted the cycle of Cu(I)/Cu(II) and Fe(II)/Fe(III), guaranteeing the regeneration of the active sites. Triple optimisation of the modified spinel oxide presented a striking oxidant utilisation efficiency with a substantial increase in the concentration of radicals. This study provides a simple and reliable reference for designing high-performance CuFe2O4 (CFO) photocatalysts for environmental remediation.

Adsorption of heavy metals by biochar in aqueous solution: A review

Heavy metal pollution (e.g., Cd, Hg, Pb, Cu, Ni, Zn, As and Cr) has become a crucial issue worldwide. Among various remediation strategies, adsorption is widely recognized for its environmental sustainability, cost-effectiveness, and operational simplicity. In this context, biochar has gained significant attention due to its promising adsorption performance. To systematically support adsorption studies, this review compiled essential models for adsorption experiments, including commonly used adsorption kinetics models, isotherm models, and thermodynamic analysis methods. Moreover, we systematically analyzed key factors affecting heavy metal adsorption by biochar, such as its physicochemical properties, environmental pH, temperature, initial concentration, dosage, and the presence of coexisting ions, to identify the conditions that govern adsorption capacity. In addition, the adsorption performance of biochar toward eight significant heavy metals is reviewed in detail, with a focus on elucidating the underlying mechanisms, including complexation, ion exchange, cation-π bonding, electrostatic interactions, and precipitation. Finally, based on identified research gaps and critical challenges, we discuss emerging research tools, including machine learning and advanced surface modifications, to guide the targeted design of biochar materials for enhanced adsorption capacity.

Application and prospect of vacuum freeze drying technology in environmental field

Vacuum freeze-drying (VFD) technology has gained extensive application across various sectors, particularly in environmental applications, where it is primarily utilized for the fabrication of environmental functional materials and the conservation of environmental organisms. This technology is applicable to soil enhancement, the remediation of aquatic pollutants, energy storage in thermoelectric materials, and the preservation of bacterial cultures. This review synthesizes the most recent advancements in VFD technology within the environmental domain, elaborating on its technical fundamentals, operational procedures, practical applications, and distinctive benefits. Furthermore, the article explores the prospective development trajectory and potential challenges for this technology in the environmental sector, offering scientific guidance for its continued application and insights into its innovative progression.

60Coγ activation of Cladophora rupestris biomass functional groups and its effect on Pb2+ adsorption

To investigate the modification of Pb2+ adsorption of the functional groups of Cladophora rupestris (C. rupestris) biomass by gamma radiation (60Coγ-ray), the interface structure, chemical properties, adsorption behaviors, and Pb2+ adsorption mechanisms of C. rupestris biomass were investigated after irradiation with varying doses of 60Coγ-ray. The results indicate that 60Coγ-ray significantly changed the surface characteristics and interfacial chemistry of the C. rupestris biomass.This led to fracturing and fragmentation that produced a larger specific surface area and more abundant pore structure, increasing the electronegativity in the C. rupestris biomass. The theoretical Pb2+ adsorption capacity increased significantly (2.6-2.9 times) after 60Coγ-ray irradiation. 60Coγ-ray caused preferential degradation of protein components in the dissolved organic matter of the C. rupestris biomass, and protein deamination increased the absorption sites of cations. In the C. rupestris biomass, 60Coγ-ray altered the elemental composition and functional groups, particularly the carbon- and oxygen-containing functional groups, to improve Pb2+ adsorption. In conclusion, 60Coγ-ray can activate the functional groups of C. rupestris biomass and improve their Pb2+ adsorption sites. This study provides new insight into modification of biomass materials for enhanced removal of heavy metals from waterbodies.

Effect of inorganic component of biochar on lead adsorption performance and the enhancement by MgO modification

Biomass-derived biochar has enormous potential for sustainable and low-cost treatment of lead-contained wastewater. In this study, corncob and cow dung-derived biochar were prepared. The increase in pyrolysis temperature could improve the porous structures, surface area, functional groups and alkalinity, and further provide a higher Pb2+ capacity in both biochars. Cow dung biochar performed better than corncob for its higher inorganic mineral content and more alkaline surface. Among them, CDB-600 performed the Langmuir maximum capacity of 357.1 mg/g, with a high surface area of 144.3 m2/g; ion exchange and precipitate were the main adsorption mechanisms. After further MgO modification, the M-CDB displayed a high surface area of 166 m2/g, and ion exchangeability and precipitate-promoting effects were improved. M-CDB performed a Langmuir maximum capacity of 833.3 mg/g. The pHpzc was found to be 10 and the adsorbents portray a very good Pb2+ adsorption selectivity among coexisting ions in the solution. The adsorption process was found to be endothermic, feasible, spontaneous and chemisorption. The fixed lead on CDB-600 was stable in water. The immobilized lead could be desorbed by acid wash. CDB-600 performed better in terms of sustainability in use, which could support its continuous application ability.

Enhanced CRC Growth in Iron-Rich Environment, Facts and Speculations

The contribution of nutritional factors to disease development has been demonstrated for several chronic conditions including obesity, type 2 diabetes, metabolic syndrome, and about 30 percent of cancers. Nutrients include macronutrients and micronutrients, which are required in large and trace quantities, respectively. Macronutrients, which include protein, carbohydrates, and lipids, are mainly involved in energy production and biomolecule synthesis; micronutrients include vitamins and minerals, which are mainly involved in immune functions, enzymatic reactions, blood clotting, and gene transcription. Among the numerous micronutrients potentially involved in disease development, the present review will focus on iron and its relation to tumor development. Recent advances in the understanding of iron-related proteins accumulating in the tumor microenvironment shed light on the pivotal role of iron availability in sustaining pathological tumor hallmarks, including cell cycle regulation, angiogenesis, and metastasis.

Efficient removal of high concentration dyes from water by functionalized in-situ N-doped porous biochar derived from waste antibiotic fermentation residue

Using biochar for dye wastewater treatment is attracting interest due to its excellent adsorption properties and low costs. In this work, a novel biochar derived from oxytetracycline fermentation residue (functionalized OFR biochar, FOBC) was investigated as a efficient adsorbent for typical dyes removal. At 25 °C, the maximum adsorption capacity calculated by Langmuir model of FOBC-3-600 for methylene blue (MB), malachite green (MG), and methyl orange (MO) reached 643.97, 617.89, and 521.03 mg/g, respectively. The kinetics and isotherm model fitting showed that the chemisorption and physisorption both occurred during the adsorption process. Dyes were efficiently adsorbed through pore filling, electrostatic attraction, π-π interactions, and surface complexation. And the cycling experiment and environmental risk assessment indicated that the FOBC-3-600 had excellent recyclability and utilization safety. Overall, this study provides a practical method to simultaneously treat the dyeing wastewater and utilize the antibiotic fermentation residue.

Efficient Removal of Tetracycline from Water by One-Step Pyrolytic Porous Biochar Derived from Antibiotic Fermentation Residue

The disposal and treatment of antibiotic residues is a recognized challenge due to the huge production, high moisture content, high processing costs, and residual antibiotics, which caused environmental pollution. Antibiotic residues contained valuable components and could be recycled. Using a one-step controllable pyrolysis technique in a tubular furnace, biochar (OSOBs) was produced without the preliminary carbonization step, which was innovative and time- and cost-saving compared to traditional methods. The main aim of this study was to explore the adsorption and removal efficiency of tetracycline (TC) in water using porous biochar prepared from oxytetracycline fermentation residues in one step. A series of characterizations were conducted on the prepared biochar materials, and the effects of biochar dosage, initial tetracycline concentration, reaction time, and reaction temperature on the adsorption capacity were studied. The experimental results showed that at 298 K, the maximum adsorption capacity of OSOB-3-700 calculated by the Langmuir model reached 1096.871 mg/g. The adsorption kinetics fitting results indicated that the adsorption of tetracycline on biochar was more consistent with the pseudo-second-order kinetic model, which was a chemical adsorption. The adsorption isotherm fitting results showed that the Langmuir model better described the adsorption process of tetracycline on biochar, indicating that tetracycline was adsorbed in a monolayer on specific homogeneous active sites through chemical adsorption, consistent with the kinetic conclusions. The adsorption process occurred on the surface of the biochar containing rich active sites, and the chemical actions such as electron exchange promoted the adsorption process.

Remediation of cadmium contaminated soil using electrokinetic-phytoremediation system with rotary switching electrodes

Considering both electrokinetic remediation and phytoremediation have limitations, an electrokinetic phytoremediation (EP) system was constructed to obtain efficient and environmentally friendly remediation results. This study indicates that the electric field can promote the absorption of Cd by ryegrass with little impact on soil physicochemical properties under the condition of rotary switching electrodes, and the accumulation of Cd in the aboveground and underground parts of ryegrass increased by 145.2% and 93.7%, respectively. The DC electric field combined with ryegrass under rotary switching electrode mode proved to be the optimal condition for the remediation of Cd contaminated soil with a remediation efficiency of 66.7%. Moreover, the rotary switching of the electrodes alleviated the suppression of the growth of ryegrass by the DC electric field. During the EP remediation process, the electric field promoted the transformation of the residue state of Cd to the other forms, which accelerated the desorption rate of Cd from the soil and facilitated the migration of Cd into plants. In conclusion, EP is a green and efficient remediation technology for heavy metal contaminated soil with good application prospects.

In situ N-doping engineered biochar catalysts for oxidation degradation of sulfadiazine via nonradical pathways: Singlet oxygen and electron transfer

Understanding the structure of non-metallic heteroatom-doped carbon catalysts and the subsequent degradation of new pollutants is crucial for designing more efficient carbon catalysts. Environmentally friendly in situ N-doped biochar catalysts were prepared for peroxymonosulfate (PMS) activation and sulfadiazine (SDZ) degradation. The acid washing process and calcination temperature of catalyst increased π-π* shake up, graphitic N percentage, specific surface area and defects, promoting the transformation of pollutant degradation mechanism from radical pathway to non-radical pathway. 100 % of the SDZ with the initial concentration of 10 mg/L was quickly degraded within 60 min using 0.2 g/L catalysts and 0.5 mM PMS. Excellent catalytic performance was attributed to singlet oxygen and electron transfer-dominated non-radical pathways. The four potential degradation pathways of SDZ were proposed, and toxicity predication indicated that overall biotoxicity of the intermediates during SDZ degradation was decreased. This research deepens our understanding of the mechanisms of non-radical pathways and guides the synthesis of carbon-based catalysts.

Machine learning screening of biomass precursors to prepare biomass carbon for organic wastewater purification: A review

In the past decades, the amount of biomass waste has continuously increased in human living environments, and it has attracted more and more attention. Biomass is regarded as the most high-quality and cost-effective precursor material for the preparation carbon of adsorbents and catalysts. The application of biomass carbon has extensively explored. The efficient application of biomass carbon in organic wastewater purification were reviewed. With briefly introducing biomass types, the latest progress of Machine learning in guiding the preparation and application of biomass carbon was emphasized. The key factors in constructing efficient biomass carbon for adsorption and catalytic applications were discussed. Based on the functional groups, rich pore structure and active site of biomass carbon, it exhibits high efficiency in water purification performance in the fields of adsorption and catalysis. In addition, out of a firm belief in the enormous potential of biomass carbon, the remaining challenges and future research directions were discussed.

Efficient Adsorption of Nitrogen and Phosphorus in Wastewater by Biochar

Nitrogen and phosphorus play essential roles in ecosystems and organisms. However, with the development of industry and agriculture in recent years, excessive N and P have flowed into water bodies, leading to eutrophication, algal proliferation, and red tides, which are harmful to aquatic organisms. Biochar has a high specific surface area, abundant functional groups, and porous structure, which can effectively adsorb nitrogen and phosphorus in water, thus reducing environmental pollution, achieving the reusability of elements. This article provides an overview of the preparation of biochar, modification methods of biochar, advancements in the adsorption of nitrogen and phosphorus by biochar, factors influencing the adsorption of nitrogen and phosphorus in water by biochar, as well as reusability and adsorption mechanisms. Furthermore, the difficulties encountered and future research directions regarding the adsorption of nitrogen and phosphorus by biochar were proposed, providing references for the future application of biochar in nitrogen and phosphorus adsorption.

Adsorption of Sb(III) and Pb(II) in wastewater by magnetic γ-Fe2O3-loaded sludge biochar: Performance and mechanisms

Magnetically modified carbon-based adsorbent (BC@γ-Fe2O3) was prepared through facile route using activated sludge biomass and evaluated for the simultaneous removal of Sb(III) and Pb(II). BC@γ-Fe2O3 exhibited outstanding Sb(III) and Pb(II) adsorption capacity when 200 mg of adsorbent was employed at pH 5.0 for 240 min, with the removal efficiency higher than 90%. The experiments demonstrated the excellent reusability and the potent anti-interference properties of the prepared absorbent. Freundlich and pseudo-second-order kinetic were prior to describe the adsorption process. The adsorption of Sb(III) and Pb(II) onto BC@γ-Fe2O3 was spontaneous and endothermic. BC@γ-Fe2O3 with high specific surface area revealed the exceptional competence to absorb Sb(III) and Pb(II) through pore filling, electrostatic adsorption and complexation. The adsorption mechanisms of Sb(III) and Pb(II) showed similarities with slight disparities. The removal of Sb(III) involved the Fe-O-Sb bond and π-π bond, while the adsorption of Pb(II) was closely related to ion exchange. Moreover, Sb(III) was oxidized to Sb(V) in a minor part during adsorption. The Fe-O-Cl active sites on BC allowed for the binding of γ-Fe2O3, guaranteeing the abundant adsorption sites and stability. BC@γ-Fe2O3 provides an efficient and green insight into the simultaneous removal of complex heavy metals with promising application in wastewater treatment.

Efficient adsorption of Cu2+ and Cd2+ from groundwater by MgO-modified sludge biochar in single and binary systems

In this study, MgO-modified sludge biochar (1MBC) prepared from sewage sludge was successfully used as an efficient adsorbent to remove heavy metals from groundwater. The adsorption performance and mechanism of 1MBC on Cu2+ and Cd2+ were investigated in single and binary systems, and the contribution of different mechanisms was quantified. Adsorption kinetics and isotherms analysis revealed that the adsorption processes of Cu2+ and Cd2+ by 1MBC followed the pseudo-second-order kinetic and Langmuir isotherm model in both systems, indicating that Cu2+ and Cd2+ were mainly controlled by chemisorption, and their theoretical maximum adsorption capacities were 240.36 and 219.06 mg·g-1, respectively. The results of the binary system showed that due to the competitive adsorption, the adsorption capacity of 1MBC for both heavy metals was lower than that of the single system, and the selective adsorption of Cu2+ was higher. The influencing variable experiments revealed that the adsorption of Cu2+ and Cd2+ by 1MBC had a wide pH adaption range and strong anti-interference ability to coexisting organics and ions. The adsorption mechanisms involved ion exchange (Cu: 47.39%, Cd: 53.17%), mineral precipitation (Cu: 35.31%, Cd: 24.18%), functional group complexation (Cu: 10.44%, Cd: 14.53%), and other possible mechanisms (Cu: 6.87%, Cd: 8.12%). Furthermore, 1MBC demonstrated excellent regeneration potential after five cycle times. Overall, the results have significant reference value for the practical application of removing heavy metals.