Struvite crystallization by using active serpentine: An innovative application for the economical and efficient recovery of phosphorus from black water

Deciphering the interplay between wastewater compositions and oxytetracycline in recovered struvite: Unveiling mechanisms and introducing control strategies

Struvite recovery from wastewater offers a sustainable phosphorus and nitrogen source, yet it harbors the challenge of variable antibiotic residues, notably oxytetracycline (OTC), increasing the ecological risk during subsequent use. Despite the need, mechanisms behind these residues and regulatory solutions remain obscure. We characterized OTC in recovered struvite and showed that increased dissolved organic matter (DOM) enhanced OTC accumulation, while PO43- suppressed it. NH4+ modulated OTC levels through the saturation index (SI), with a rise in SI significantly reducing OTC content. Additionally, excess Mg2+ formed complexes with OTC and DOM (humic acid, HA), leading to increased residue levels. Complexation was stronger at higher pH, whereas electrostatic interactions dominated at lower pH. The primary binding sites for antibiotics and DOM were Mg-OH and P-OH groups in struvite. OTC's dimethylamino, amide, and phenolic diketone groups primarily bound to struvite and DOM, with the carboxyl group of DOM serving as the main binding site. Mg2+ complexation was the primary pathway for OTC transportation, whereas electrostatic attraction of PO43- dominated during growth. Controlling magnesium (Mg) dosage and adjusting pH were effective for reducing OTC in recovered products. Our findings provided insights into the intricate interactions between struvite and antibiotics, laying the groundwork for further minimizing antibiotic residues in recovered phosphorus products.

Hybrid method integrating adsorption and chemical precipitation of heavy metal ions on polymeric fiber surfaces for highly efficient water purification

A lot of research has been focused on increasing the specific surface area of adsorbents over a long period of time to remove heavy metal ions from wastewater using the adsorbent. However, porous adsorbents with high specific surface area have demonstrated drawbacks in water purification processes, such as high pressure drop and limitations in the adsorption capacity of heavy metal ions. In recent years, a mechanism-based convergence method involving adsorption/chemical precipitation has emerged as a promising strategy to surmount the constraints associated with porous adsorbents. The mechanism involves amine groups on chelating fibers dissociating OH- ions from water molecules, thereby raising the pH near the fibers. This elevated pH promotes the crystallization of heavy metal ions on the fiber surfaces. The removal of heavy metal ions proceeds through a sequence of adsorption and chemical precipitation processes. An adsorbent based on chelating fibers, integrating adsorption technology with chemical precipitation, demonstrates superior performance in removing significant quantities of heavy metal ions (ca. 1000-2000 mg/g for Cd2+, Cu2+ and Pb2+) when compared to developed porous adsorbents (ca. 50-760 mg/g for same ions). This review paper introduces advanced polymer fibers endowed with the capability to integrate hybrid technology, delves into the mechanism of hybrid technology, and examines its application in process technology for the effective removal of heavy metal ions. The versatility of these advanced fibers extends far beyond the removal of heavy metal ions in water treatment, making them poised to garner significant attention from researchers across diverse fields due to their broad range of potential applications. After further processes involving the removal of templates from chelating polymeric fibers used as supports and the reduction of precipitated heavy metal oxide crystals, the resulting heavy metal crystals can exhibit thin walls and well-interconnected porous structures, suitable for catalytic applications.

Efficient incorporation of highly migratory thallium into struvite structure: Unraveling the stabilization mechanisms from a mineralogical perspective

The remediation of high-concentration thallium (Tl+) contaminated wastewater is a critical environmental concern. Current research emphasizes the effectiveness of adsorption and oxidation methods for Tl+ treatment, yet challenges persist in enhancing their performance. This study explores the feasibility of emergency Tl+ wastewater treatment and elucidates the mechanisms of Tl+ incorporation into mineral structures, with a focus on the struvite mineral as a framework for Tl+ integration via NH4+ ion exchange. To assess the efficacy and mechanisms of Tl+ immobilization, we utilized comprehensive analytical techniques, including X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS), Thermogravimetric Analysis (TG), and Density Functional Theory (DFT) calculations. The findings reveal that struvite adsorbs Tl+ onto its surface, followed by an ion exchange process between monovalent cations (NH4+/K+) within the structure and Tl+. Ultimately, Tl+ is incorporated in the form of a (NH4,Tl)MgPO4 solid solution within the structure, achieving a remarkable maximum incorporation capacity of 320.56 mg/g, which significantly surpasses the capacity of typical adsorbents. The findings demonstrate significant Tl+ incorporation, validating the approach for emergency wastewater treatment and suggesting the potential of mineralogy in environmental remediation. This research contributes to advancing heavy metal wastewater treatment strategies, offering a foundation for further investigation.

Treatment techniques and resource recovery of source-separated urine: a bibliometric analysis and literature review

Human urine, which is high in nutrients, acts as a resource as well as a contaminant. Indiscriminate urine discharge causes environmental pollution and wastes resources. To elucidate the research status and developmental trajectory of source-separated urine (SSU) treatment and recovery, this study was based on the Web of Science Core Collection (WOSCC) database and used the bibliometric software VOSviewer and CiteSpace to conduct a comprehensive and in-depth bibliometric analysis of the related literature in this field. The findings revealed a general upward trend in SSU treatment and recovery from 2000 to 2023. The compendium of 894 scholarly articles predominantly focused on the disciplines of Environmental Sciences, Environmental Engineering, and Water Resources. China and the USA emerged as the foremost contributors. Keyword co-occurrence mapping, clustering, and burst analysis have shown that the recovery of nitrogen and phosphorus from urine is currently the main focus, with future prospects leaning toward the retrieval of biochemicals and chemical energy. This study systematically categorizes and compares the developmental status, current advancements, and research progress in this field. The findings of this study provide a valuable reference for understanding developmental pathways in this field of research.

Phosphorus recovery from sewage sludge via Mg-air battery system

A pressing issue in contemporary society is the resource scarcity of phosphorus. Operating on the principle of electrochemical reactions between Mg as the anode and oxygen from air as the cathode, Mg-air batteries (MAB) have been employed to provide new prospects for phosphorus recovery in struvite form. Different phosphorus concentrations and reaction time impact struvite generation in MAB systems; however, the exact mechanism has rarely been investigated. We investigated how varying the initial phosphorus concentration and the reaction time affects phosphorus recovery, electricity generation, and the efficiency of struvite production in MAB. Additionally, we examine the impact of solid carbon sources on phosphorus transformation in sludge. The findings revealed that the incorporation of solid carbon sources facilitated the release of phosphate by changing phosphorus speciation. The electrolyte derived from the conditioned sludge filtrate exhibited a remarkable phosphorus removal efficiency of 91.7 % within 1 h, yielding the highest struvite purity of ∼70 %, whereas that using raw sludge filtrate or extending the reaction time was found to be less effective, even reducing struvite formation. Furthermore, different electrolytes influence the system's ability to passivate anode, and electrolytes with higher phosphorus concentrations have better electricity production performance. The results by Visual MINTEQ model confirmed that longer reaction times and lower initial phosphorus concentrations can negatively affect struvite formation by introducing Mg3(PO4)2 and Mg(OH)2. The integration of agricultural waste as carbon sources with MAB for phosphorus recovery represents a potential methodology for struvite recuperation from sewage sludge, thereby heralding a sustainable strategy for resource recovery.

Structural design of La2(CO3)3 loaded magnetic biochar for selective removal of phosphorus from wastewater

High levels of phosphorus released into the environment can cause eutrophication issues in wastewater, therefore discharge concentrations of such element are regulated in many countries. This study addresses the pressing need for effective phosphorus removal methods by developing a novel La2(CO3)3 and MnFe2O4 loaded biochar composite (LMB). A remarkable adsorption capacity towards the three forms of phosphorus from wastewater, including phosphate, phosphite, and etidronic acid monohydrate (as a representative of organic phosphorus), was exhibited by LMB (88.20, 16.35, and 15.95 mg g-1, respectively). The high saturation magnetization value (50.17 emu g-1) highlighted the easy separability and recyclability of the adsorbent. The adsorption process was well described by the Langmuir isotherm model and the pseudo-second-order kinetic model, which mainly involved chemisorption. Characterization results confirm the effective loading of La2(CO3)3 with ligand exchange and electrostatic attraction identified as the primary mechanisms. Importantly, the LMB demonstrated exceptional selectivity for phosphorus in wastewater samples containing various substances, exhibiting minimal interference from competing ions (Cl-, NO3-, SO42-, and CO32-). These findings enhance the understanding of LMB's application in efficient wastewater phosphorus removal. Holding significant promise in wastewater remediation, the LMB acts as an effective adsorbent, contributing substantially to the prevention and control of various types of phosphorus pollutants, thereby mitigating wastewater eutrophication.

Phosphorus removal from water by the metal-organic frameworks (MOFs)-based adsorbents: A review for structure, mechanism, and current progress

Efficacious phosphate removal is essential for mitigating eutrophication in aquatic ecosystems and complying with increasingly stringent phosphate emission regulations. Chemical adsorption, characterized by simplicity, prominent treatment efficiency, and convenient recovery, is extensively employed for profound phosphorus removal. Metal-organic frameworks (MOFs)-derived metal/carbon composites, surpassing the limitations of separate components, exhibit synergistic effects, rendering them tremendously promising for environmental remediation. This comprehensive review systematically summarizes MOFs-based materials' properties and their structure-property relationships tailored for phosphate adsorption, thereby enhancing specificity towards phosphate. Furthermore, it elucidates the primary mechanisms influencing phosphate adsorption by MOFs-based composites. Additionally, the review introduces strategies for designing and synthesizing efficacious phosphorus capture and regeneration materials. Lastly, it discusses and illuminates future research challenges and prospects in this field. This summary provides novel insights for future research on superlative MOFs-based adsorbents for phosphate removal.

A review of struvite crystallization for nutrient source recovery from wastewater

Nutrient recovery from wastewater not only reduces the nutrient load on water resources but also alleviates the environmental problems in aquatic ecosystems, which is a solution to achieve a sustainable society. Besides, struvite crystallization technology is considered a potential nutrient recovery technology because the precipitate obtained can be reused as a slow-release fertilizer. This review presents the basic properties of struvite and the theory of the basic crystallization process. In addition, the possible influencing variables of the struvite crystallization process on the recovery efficiency and product purity are also examined in detail. Then, the advanced auxiliary technologies for facilitating the struvite crystallization process are systematically discussed. Moreover, the economic and environmental benefits of the struvite crystallization process for nutrient recovery are introduced. Finally, the shortcomings and inadequacies of struvite crystallization technology are presented, and future research prospects are provided. This work serves as the foundation for the future use of struvite crystallization technology to recover nutrients in response to the increasingly serious environmental problems and resource depletion.

Progress in the preparation, application, and recycling of black phosphorus

Black phosphorus nanosheets (BPNSs) are a new member of the nanomaterial family, and they have good development potential in electrochemistry, electronics, optoelectronics, environmental protection, biomedical, and other fields because of their bandgap width, high anisotropy, broad optical absorption, high carrier mobility and many other features. Although many articles have been published about the preparation and application of BPNSs, these aspects have not been elucidated, and we aimed to fill this knowledge gap in this review. First, we used VOSviewer software to sort out articles published in the past 5 years and drew a literature map, which allowed us to sort out the relationship between various studies related to BPNSs, and reflect on the research focus in recent years. Because BPNSs must be made from black phosphorus (BP), and BPNSs are a nano form of BP, the collation of the BP preparation scheme was also helpful for the related research on BPNSs. This paper introduces the preparation of bulk BP and BPNSs, analyzes and compares the advantages and disadvantages of each method, and points out the most promising methods in the future. Then, we propose improvement directions for this method. We also introduce the characterization of BPNSs and combine it with the subsequent photocatalytic application of BPNSs. As a new material, the effect of BPNSs on the environment is still unknown; thus, an end treatment scheme for BPNSs is summarized according to existing methods. Based on the experience of nanomaterial treatment, this paper proposes a research focus for the end treatment of BPNSs in the future, providing a reference scheme for the end treatment of other nanomaterials. Finally, we summarize the full text and propose recommended methods and improvement plans.