Synthesis of co-pyrolyzed biochar using red mud and peanut shell for removing phosphate from pickling wastewater: Performance and mechanism

Hydrogenated red mud biochar as visible-light-driven peroxymonosulfate (PMS) activators for efficient degradation of antibiotic: Resource utilization, mechanism insights and toxicity assessment

The drawbacks of low efficiency, high cost, and high energy consumption have always been main concerns for the treatment of antibiotic wastewater and massive solid wastes. In this work, a novel recyclable catalyst ((RM/BC)H) was proposed by "To treat waste with waste" and "Resource oriented utilization of solid waste". Through hydrogenation and co-pyrolysis, the new catalyst was produced by industrial waste of red mud (RM) and biomass waste as the raw materials. And then, peroxymonosulfate (PMS) was activated by (RM/BC)H to degrade tetracycline hydrochloride (TCH) aqueous solution under LED-vis light condition. The results demonstrated that the (RM/BC)H + PMS + LED-vis light system has exhibited an excellent degradation efficiency with 82.6% for TCH (TOC removal efficiency 45.6%), and the efficiency kept stable at 80% after 5 cycles. Furthermore, EPR detection and quenching experiments revealed that SO4•-, •OH, O2•- and 1O2 were generated in this system and co-participated in TCH degradation. Hydrogenation modification (RM/BC)H could improve the electron transfer efficiency and electric transfer ability of the materials. Meanwhile, the DFT calculations confirmed that Fe2+ was more conducive to the activation of PMS, and the synergistic effect of LED-vis light and PMS to form an internal cycle of Fe3+ and Fe2+ were favorable to the stability of the material. This study provides a feasible opinion on the economical and efficient degradation of antibiotic wastewater.

Phosphorus recovery and reuse: Innovating with biochar in the circular economy

Global challenges of phosphorus pollution and scarcity underscore an urgent need for the efficient recycling of this critical resource. Biochar, a sustainable and economical material, has demonstrated significant potential as an adsorbent for phosphorus, offering a viable solution for its recovery from wastewater. Various techniques have been explored to improve the ability of biochar to adsorb inorganic phosphate. While numerous studies have reviewed methods of biochar modification, the underlying adsorption mechanisms, and the thermodynamics and kinetics involved, a thorough examination that addresses the practical challenges of real-world wastewater treatment is currently lacking. This review aims to fill this gap by quantitatively analyzing the impact of coexisting species in wastewater on the adsorption of phosphate and by exploring the potential for simultaneous removal of other contaminants, such as nutrients, heavy metals, and dissolved organic matter. The review also discusses factors that affect the desorption of phosphate from biochar and presents practical applications for biochars post-adsorption. These applications include their use as slow-release phosphorus fertilizers, additives in concrete, and as novel adsorbents for the removal of heavy metals. This comprehensive analysis serves to synthesize current research on phosphate recovery by biochars and to propose practical uses for the adsorbed phosphorus, thereby guiding the development of biochar adsorption technology towards more effective and practical phosphorus management strategies.

Effects of flotation reagents with aniline aerofloat and ammonium dibutyl dithiophosphate on a constructed rapid infiltration system: Performance and microbial metabolic pathways

Aniline aerofloat (AAF) and ammonium dibutyl dithiophosphate (ADD) are the key flotation reagents in mineral processing. This study investigated the performance of the constructed rapid infiltration systems with coke and red mud as adsorbents for treatment AAF and ADD wastewater. Meanwhile, the effects of AAF and ADD on the microbial metabolic pathways of the systems were unraveled. Results showed that the AAF concentration in influent was 25 mg/L, which promoted chemical oxygen demand (COD) and total phosphorus (TP) removal of the A column (coke) and B column (red mud). While the COD and TP removal of the C column (coke) and D column (red mud) were inhibited with ADD concentration increasing to 50 mg/L and 100 mg/L. The AAF reduced the binding energy of coke C-O bond by 0.9 eV, and down-regulated the C-C bond ratio by 40.72%. The dominant phyla in the columns were Pseudomonadota and Actinomycetota. The pore structure of coke was more conducive to the growth of the Pseudomonadota, while the metal composition of red mud was more conducive to the redox reaction of microorganisms. The presence of phosphofructokinase (2.7.1.11)-related genes was up-regulated in column C compared to other columns. The ADD was beneficial to the expression of norC and nosZ functional genes during nitrogen metabolism process. In contrast, phosphorus metabolism genes were more expressed in the red mud column for treatment AAF wastewater. This study reveals the potential of coke and red mud for the treatment of flotation reagents wastewater, while providing a theoretical basis for the optimal selection of filler types in the constructed rapid infiltration systems.

Unlocking the potential of environmentally friendly adsorbent derived from industrial wastes: A review

With increasing urbanization and industrialization, growing amounts of industrial waste, such as red mud (RM), fly ash (FA), blast furnace slag (BFS), steel slag (SS), and sludge, are being produced, exposing substantial threats to the environment and human health. Given that numerous researchers associate with conventional adsorbents, developing and utilizing industrial wastes derived from adsorption technology still has received limited attention. Utilizing this waste contributes to developing alternative materials with superior performance and significantly reduces the volume of solid waste. The excellent physical and chemical characteristics of these wastes are also investigated in this paper. This review attempts to demonstrate a comprehensive overview of the application of industrial waste-based adsorbent in the adsorption process for removing organic pollutants, dyes, metallic ions, non-metallic ions, and radioactive substances. In addition, industrial waste-based adsorbents are among the most promising and applicable techniques for pollutant removal, offering remarkable adsorption efficiency, rich surface chemistries, reasonable cost, simple operation, and low energy consumption. This review summarizes state-of-the-art advancements in engineered adsorbents (including physical and chemical modifications). It provides a holistic view regarding a comprehensive understanding of the mechanism involved in adsorption for water remediation. The challenges and the prospects for future research in applying these adsorbents are also elucidated, contributing to sustainable waste management and environmental sustainability.

Innovative Adsorbents for Pollutant Removal: Exploring the Latest Research and Applications

The growing presence of diverse pollutants, including heavy metals, organic compounds, pharmaceuticals, and emerging contaminants, poses significant environmental and health risks. Traditional methods for pollutant removal often face limitations in efficiency, selectivity, and sustainability. This review provides a comprehensive analysis of recent advancements in innovative adsorbents designed to address these challenges. It explores a wide array of non-conventional adsorbent materials, such as nanocellulose, metal-organic frameworks (MOFs), graphene-based composites, and biochar, emphasizing their sources, structural characteristics, and unique adsorption mechanisms. The review discusses adsorption processes, including the basic principles, kinetics, isotherms, and the factors influencing adsorption efficiency. It highlights the superior performance of these materials in removing specific pollutants across various environmental settings. The practical applications of these adsorbents are further explored through case studies in industrial settings, pilot studies, and field trials, showcasing their real-world effectiveness. Additionally, the review critically examines the economic considerations, technical challenges, and environmental impacts associated with these adsorbents, offering a balanced perspective on their viability and sustainability. The conclusion emphasizes future research directions, focusing on the development of scalable production methods, enhanced material stability, and sustainable regeneration techniques. This comprehensive assessment underscores the transformative potential of innovative adsorbents in pollutant remediation and their critical role in advancing environmental protection.

Metal element-based adsorbents for phosphorus capture: Chaperone effect, performance and mechanism

Excessive phosphorus (P) enters the water bodies via wastewater discharges or agricultural runoff, triggering serious environmental problems such as eutrophication. In contrast, P as an irreplaceable key resource, presents notable supply-demand contradictions due to ineffective recovery mechanisms. Hence, constructing a system that simultaneously reduce P contaminants and effective recycling has profound theoretical and practical implications. Metal element-based adsorbents, including metal (hydro) oxides, layered double hydroxides (LDHs) and metal-organic frameworks (MOFs), exhibit a significant chaperone effect stemming from strong orbital hybridization between their intrinsic Lewis acid sites and P (Lewis base). This review aims to parse the structure-effect relationship between metal element-based adsorbents and P, and explores how to optimize the P removal properties. Special emphasis is given to the formation of the metal-P chemical bond, which not only depends on the type of metal in the adsorbent but also closely relates to its surface activity and pore structure. Then, we delve into the intrinsic mechanisms behind these adsorbents' remarkable adsorption capacity and precise targeting. Finally, we offer an insightful discussion of the prospects and challenges of metal element-based adsorbents in terms of precise material control, large-scale production, P-directed adsorption and effective utilization.

Municipal sludge biochar skeletal sodium alginate beads for phosphate removal

A novel Fe/La decorative biochar filled in sodium alginate beads (SA-KBC-Fe/La) was prepared by a simple sol-gel method and applied to adsorb phosphate (P) efficiently from water in this study. The morphology, structure and chemical component of the hydrogel beads were characterized in detail. And the synthesized bead exhibited easy separation and high P uptake of 46.65 mg/g when the Fe: La was of 1: 2 at 298 K with initial P of 100 mg/L, which was much higher than SA gel bead. The adsorption showed that the optimal pH was 6, and the adsorption was met with pseudo-second-order kinetics and Langmuir isothermal models, indicating a chemical adsorption process. The adsorption capacity remained 82 % after 5 cycles of adsorption. The adsorption mechanism of P was mainly of ligand exchange and electrostatic attraction. Compared with other reported adsorbents, the modification of Fe/La could enhance the mechanical property of SA-KBC-Fe/La beads with increasing active sites. Additionally, the involved biochar could lead to excellent thermal stability and hierarchical porous structure of beads with larger specific surface area (54.22 m2/g). The study could provide new ideas for P removal and strategy for the final disposal of municipal sludge.

Acid treatment for enhancing Hg0 removal efficiency of chlorine-loaded biochar: mechanism and kinetic analysis

Adsorbents modified solely with chlorine have limited effectiveness in removing mercury at high temperatures. This study aims to investigate the influence of various acid (HNO3, H2SO4, and H2O2) loadings on the removal efficiency of mercury from NH4Cl-modified adsorbents. The objective is to develop rice straw carbon adsorbents that are both more efficient and cost-effective. The experiments were conducted on a fixed bed experimental platform, with SEM and BET to observe the physical property changes of the modified char samples. XPS analysis was employed to analyze the effects of oxygen, chlorine, and sulfur functional groups. Additionally, a kinetic model was used to investigate the interaction mechanism between the adsorbent and mercury. The findings demonstrate that co-modification surpasses the use of NH4Cl alone, with the combination of NH4Cl and HNO3 yielding the best results. Co-modification enhances the development of a more refined and compact pore structure on the char surface, promoting the physical adsorption of mercury. Moreover, an increased presence of chlorine and oxygen functional groups is observed on the char surface, particularly in the NH4Cl and HNO3 co-modified samples, further enhancing the chemical adsorption capacity of the char. The results from the kinetic analysis support this conclusion. Furthermore, the adsorption process of Hg0 relies on both external mass transfer and chemical adsorption, with the chemical adsorption process playing a more significant role as the controlling factor.

Insight into the impacts of pyrolysis time on adsorption behavior of Pb2+ and Cd2+ by Mg modified biochar: Performance and modification mechanism

Co-pyrolysis biomass and alkaline metals can effectively improve the adsorption performance of heavy metals (HM). Nevertheless, the researchers have ignored the relationship between the change of alkaline metal morphology and adsorption during pyrolysis. In this article, according to control the pyrolysis time (30, 60, and 180 min) synthesized Magnesium (Mg) modified biochar (MBCX) by using MgCl2·6H2O and soybean straw under 400 °C. The sorption capacities of MBC60 and MBC180 for Pb2+/Cd2+ increased by 38.65%/213.29%, 44.57%/230.36%, and the selectivity coefficient of Pb2+/Cd2+ increased by 113.28%/209.49%, 213.58%/253.62%, respectively, compared with MBC30. Additionally, the characterization results demonstrated that MgO dominated the surface phases of MBC60 and MBC180, whereas MgCl2 dominated the surface phases of MBC30. Moreover, according to the results of DFT calculation, the adsorption energy (Eads) of MgO for Pb2+ (-0.537 eV) and Cd2+ (-0.347 eV) was lower than that of MgCl2 (Pb2+: 0.37 eV, Cd2+: -0.185 eV), so that, MBC60 and MBC180 had higher sorption capacities for Pb2+ and Cd2+ than MBC30. Therefore, this work provides a new sight to clear the mechanism for modified biochar by alkali metal oxide and practical and theoretical guidance for adsorbent preparation with high adsorption ability for HMs.

Characterization of Magnetic Biochar Modified Using the One-Step and Electrochemical Methods and Its Impact on Phosphate Adsorption

The properties and phosphate adsorption capability of the one-step method and electrochemical method in modifying peanut shell biochar have been determined. The one-step method deposits MgO and Fe3O4 onto biochar through chemical impregnation and regularly affects the functional groups and magnetic separation of biochar, thereby enhancing its ability to adsorb phosphate. In contrast, the electrochemical method is not favorable for modifying functional groups of biochar but can promote phosphate adsorption because of the formation of MgFe2O4 and Fe3O4 using electrolysis. The adsorption isotherm and kinetics data suggest that adsorption is monolayer onto a homogeneous surface and phosphate adsorption could be controlled by chemical processes. Biochar with the addition of both Fe2+ and Mg2+ shows better phosphate adsorption capability than those with barely any Fe2+ additions. It was concluded that the one-step method is a better modification method than the electrochemical method for enhancing the phosphate adsorption capability of biochars.