Efficient and sustainable phosphate removal from water by small-sized Al(OH)3 nanocrystals confined in discarded Artemia Cyst-shell: Ultrahigh sorption capacity and rapid sequestration

Sustainable adsorbent frameworks based on bio-resourced materials and biodegradable polymers in selective phosphate removal for waste-water remediation

Phosphorus to an optimum extent is an essential nutrient for all living organisms and its scarcity may cause food security, and environmental preservation issues vis-à-vis agroeconomic hurdles. Undesirably excess phosphorus intensifies the eutrophication problem in non-marine water bodies and disrupts the natural nutrient balance of the ecosystem. To overcome such dichotomy, biodegradable polymer-based adsorbents have emerged as a cost-effective and implementable approach in striking a "desired optimum-undesired excess" balance pertaining to phosphate in a sustainable manner. So far, the reports on adopting such adsorbent-approach for wastewater remediation remained largely scattered, unstructured, and poorly correlated. In this background, the contextual review comprehensively discusses the current state-of-the-art in utilizing biodegradable polymeric frameworks as an adsorbent system for phosphate removal and its efficient recovery from the aquatic ecosystem, while highlighting their characteristics-specific functional efficiency vis-à-vis easiness of synthetic and commercial viability. The overview further delves into the sources and environmental ramifications of excessive phosphorus in water bodies and associated mechanistic pathways of phosphorus removal via adsorption, precipitation, and membrane filtration enabled by biodegradable (natural and synthetic) polymeric substrates. Finally, functionality optimization, degradability tuning, and adsorption selectivity of biodegradable polymers are highlighted, while aiming to strike a balance in "removal-recovery-reuse" dynamics of phosphate. Thus, the current review not only paves the way for future exploration of biodegradable polymers in sustainable cost-effective adsorbents for phosphorus removal but also can serve as a guide for researchers dealing with this critical issue.

Enhanced sequestration of Pb2+ and Cu2+ by Artemia cyst shell supported nano-Mg composite and the potential photocatalytic performance of carbonized exhausted-adsorbent

This study reported a new strategy for enhanced Pb2+ and Cu2+ sequestration by Artemia cyst shell (shell) supported nano-Mg from aqueous solutions and the carbonated exhausted-adsorbents sequenced potential application in photo-catalyst, which obtained two expected results. One is that the immobilization of nano-Mg onto Artemia cyst shell (shell-Mg) can greatly strengthen the adsorption effect of the neat cyst shell on Pb2+ and Cu2+. The adsorption capacities of shell-Mg for both metal ions reached to 622.01 and 313.91 mg/g, which was 10-15 and 30-50 times that of the neat shell respectively. And shell-Mg has strong selectivity, which was approximately 2-4 times that of shell. The shell-Mg can be used to retrieve Pb2+ and Cu2+ from aqueous solutions efficiently. Another is that the carbonated exhausted-adsorbents (C-shell-Mg-Pb and C-shell-Mg-Cu) showed their potential photocatalytic degradation effects on congo red under pH = 4 condition, the decolorization rate reached to 61.19% and 80.39% respectively. Reuse of exhausted adsorbents can avoid the secondary pollution caused by the regeneration, extend the utilization value of exhausted adsorbents, and provide a new viewpoint for the reuse of spent bio-nanomaterial adsorbents.

Efficient Removal and Recovery of Ag from Wastewater Using Charged Polystyrene-Polydopamine Nanocoatings and Their Sustainable Catalytic Application in 4-Nitrophenol Reduction

This study addresses the long-standing challenges of removing and recovering trace silver (Ag) ions from wastewater while promoting their sustainable catalysis utilization. We innovatively developed a composite material by combining charged sulfonated polystyrene (PS) with a PDA coating. This composite serves a dual purpose: effectively removing and recovering trace Ag+ from wastewater and enabling reused Ag for sustainable applications, particularly in the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The PS-PDA demonstrated exceptional selectivity to trace Ag+ recycling, which is equal to 14 times greater than the commercial ion exchanger. We emphasize the distinct roles of different charged functional groups in Ag+ removal and catalytic reduction performance. The negatively charged SO3H groups exhibited the remarkable ability to rapidly enrich trace Ag ions from wastewater, with a capacity 2-3 times higher than that of positively-N+(CH3)3Cl and netural-CH2Cl-modified composites; this resulted in an impressive 96% conversion of 4-NP to 4-AP within just 25 min. The fixed-bed application further confirmed the effective treatment capacity of approximately 4400 L of water per kilogram of adsorbent, while maintaining an extremely low effluent Ag+ concentration of less than 0.1 mg/L. XPS investigations provided valuable insights into the conversion of Ag+ ions into metallic Ag through the enticement of negatively charged SO3H groups and the in situ reduction facilitated by PDA. This breakthrough not only facilitates the efficient extraction of Ag from wastewater but also paves the way for its environmentally responsible utilization in catalytic reactions.

Studies on ultrafast and remarkable removal of phosphate from sewage water by metal-organic frameworks

In the proposed research, a lanthanum-doped metal-organic framework (La-ATP) has been synthesised to remove phosphate from contaminated aqueous solutions. La-ATP was synthesised by a green energy-saving route using microwave irradiation and exhibited a phenomenal sorption capacity of 290 mg/g for the removal of phosphate. At a minimal dose of 0.1 g/L, 25 mg/L of phosphate gets reduced to 6.3 mg/L within 5 min and reaches equilibrium in 25 min. The isoelectric point of La-ATP was found to be 8.99, and it is efficient in removing phosphate over a wide range of pH 5-10. The existence of commonly occurring competing anions like sulphate, fluoride, chloride, arsenate, bicarbonate, and nitrate does not affect the uptake capacity of La-ATP towards phosphate ions. Furthermore, the robustness of La-ATP is demonstrated by its applicability to remove phosphate from real-life sewage water by reducing 10 mg/L of phosphorus from sewage water to < 0.02 mg/L. The primary mechanism governing phosphate removal was found to be ionic interaction and ligand exchange. Therefore, La-ATP can be considered a viable candidate for the treatment of eutrophic water streams because of its high sorption capacity, super-fast kinetics, and adaptability to contaminated sewage.

Enhanced adsorption and co-adsorption of heavy metals using highly hydrophilicity amine-functionalized magnetic hydrochar supported MIL-53(Fe)-NH2: performance, kinetics, and mechanism studies

It is a "kill two birds with one stone" method to convert invasive plants into hydrochar via hydrothermal carbonization as well as coinciding with 3R rules (reduction, recycling, and reuse). In this work, a series of hydrochars (pristine, modified, and composite) derived from invasive plants Alternanthera philoxeroides (AP) were prepared and applied to the adsorption and co-adsorption of heavy metals (HMs) such as Pb(II), Cr(VI), Cu(II), Cd(II), Zn(II), and Ni(II). The results show that MIL-53(Fe)-NH₂- magnetic hydrochar composite (M-HBAP) displayed a strong affinity for HMs, which the maximum adsorption capacities for HMs were 153.80 (Pb(II)), 144.77 (Cr(VI)), 80.58 (Cd(II)), 78.62 (Cu(II)), 50.39 (Zn(II)), and 52.83(Ni(II)) mg/g (c₀ = 200 mg/L, t = 24 h, T = 25 ℃, pH = 5,2,6,4,6,5). This may be because the doping of MIL-53(Fe)-NH₂ enhanced the surface hydrophilicity of hydrochar, which allows hydrochar to disperse in the water within 0.12 s and possessed excellent dispersibility compared with pristine hydrochar (BAP) and amine-functionalized magnetic modified hydrochar (HBAP). Furthermore, the BET surface area of BAP was improved from 5.63 to 64.10 m²/g after doing MIL-53(Fe)-NH₂. M-HBAP shows a strong adsorption effect on the single HMs system (52-153 mg/g), while it decreased significantly (17-62 mg/g) in the mixed HMs system due to the competitive adsorption. Cr(VI) can produce strong electrostatic interaction with M-HBAP, Pb(II) can react with CaC₂O₄ on the surface of M-HBAP for chemical precipitation, and other HMs can react with functional groups on the surface of M-HBAP for complexation and ion exchange. In addition, five adsorption-desorption cycle experiments and vibrating sample magnetometry (VSM) curves also proved the feasibility of the M-HBAP application.

Direct Atomic-Scale Insight into the Precipitation Formation at the Lanthanum Hydroxide Nanoparticle/Solution Interface

Understanding precipitation formation at lanthanum hydroxide (La(OH)₃) nanoparticle-solution interfaces plays a crucial role in catalysis, adsorption, and electrochemical energy storage applications. Liquid-phase transmission electron microscopy enables powerful visualization with high resolution. However, direct atomic-scale imaging of the interfacial metal (hydro)oxide nanostructure in solutions has been a major challenge due to their beam-driven dissolution. Combining focused ion beam and aberration-corrected high-angle annular dark-field scanning transmission electron microscopy, we present an atomic-scale study of precipitation formation at La(OH)₃ nanoparticle interfaces after reaction with phosphate. The structure transformation is observed to occur at high- and low-crystalline La(OH)₃ nanoparticle surfaces. Low-crystalline La(OH)₃ mostly transformed and high-crystalline ones partly converted to LaPO₄ precipitations on the outer surface. The long-term structure evolution shows the low transformation of high-crystalline La(OH)₃ nanoparticles to LaPO₄ precipitation. Because precipitation at solid-solution interfaces is common in nature and industry, these results could provide valuable references for their atomic-scale observation.

Neuroprotective properties of borax against aluminum hydroxide-induced neurotoxicity: Possible role of Nrf-2/BDNF/AChE pathways in fish brain

The current study was designed to assess the possible neuroprotective effect of borax (BX) against the toxicity of aluminum hydroxide [AH, Al (OH)₃] on brain of rainbow trout (Oncorhynchus mykiss) with multibiomarker approaches. For this purpose, the presence of the neuroprotective action by BX against the AH exposure was assessed by the activities of catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), myeloperoxidase (MPO), acetylcholinesterase (AChE). In addition, we evaluated glutathione (GSH), malondialdehyde (MDA), DNA damage (8-OHdG), apoptosis (caspase 3), tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), nuclear factor erythroid-2 (Nrf-2), and brain-derived neurotrophic factor (BDNF) levels in 96 h semi-static treatment. In the 48th and 96th hour samplings, apoptosis induced by AH in the Nrf-2/BDNF/AChE pathways in rainbow trout brain tissue was revealed by DNA damage, enzyme inhibitions and lipid peroxidations. On the contrary applications of BX supported antioxidant capacity without leading apoptosis, lipid peroxidation, inflammatory response and DNA damage. BX also increased the BDNF levels and AChE activity. Moreover, BX exerted a neuroprotective effect against AH-induced neurotoxicity via down-regulating cytokine-related pathways, minimising DNA damage, apoptosis as well as up-regulating GSH, AChE, BDNF and antioxidant enzyme levels. It can be concluded that the combination of borax with AH modulated the toxic effects of AH.

Fe12LaO19 fabricated biochar for removal of phosphorus in water and exploration of its adsorption mechanism

Phosphorus (P) runoff from untreated wastewater and agricultural runoff has become an issue of concern because excessive P is detrimental to the health of water bodies and aquatic organisms such as fishes. Hence, different methods are being developed to salvage this challenge. However, most of the methods are expensive, while some are unsustainable. In this study, a simple method was employed in fabricating an absorbent through the co-precipitation of iron and lanthanum on the matrix of biochar prepared from the spent coffee ground for P uptake. The adsorbent named Fe₁₂LaO₁₉@BC was able to attain equilibrium fast within 60 min when used to adsorb P with 98% P removal within the first 30 min Fe₁₂LaO₁₉@BC also maintained high P adsorption across a pH range of 3-7. In the presence of other anions (SO₄^2-, CO₃^2-, NO₃^-, Cl^-, HCO₃^-) in the solution, Fe₁₂LaO₁₉@BC enabled 71.5-97.8% uptake of P. 81.58 mg P/g maximum adsorption capacity at was reached at 40 °C. The reusability test reveals that about 60% of P uptake was maintained after five adsorption cycles with almost an undisturbed desorption efficiency. The negative value of ΔG°, as shown by the thermodynamic analysis, indicates a favorable and spontaneous reaction during P removal by Fe₁₂LaO₁₉@BC. The XRD analysis showed a major peak corresponding to Fe₁₂LaO_19, which is believed to have facilitated the adsorption of P. The adsorption was controlled by multiple mechanisms. An overview of the study indicates Fe₁₂LaO₁₉@BC as a promising adsorbent for the removal of P in the water.

Improved fractionation method using amphipathic NDAM for the efficient separation of disinfection by-product precursors in natural organic matter

The hydrophilic substances in natural organic matter (NOM) are the main precursor of disinfection by-products (DBPs) formed during disinfection processes. The fractionation of the components in NOM based on hydrophilicity contributes to elaborating the behavior of NOM during disinfection. However, the traditional NOM fractionation method using two hydrophobic resins of DAX-8 and XAD-4 lays emphasis on the separation of hydrophobic substances, limiting the thorough study of the hydrophilic components in NOM. In this work, the amphiphilic resin NDAM was employed as a replacement of XAD-4 to realize more thorough separation of the hydrophilic substances. Compared with the divinylbenzene (DVB) structure of XAD-4, the NDAM possesses a more hydrophilic skeleton of N-vinylpyrrolidone (NVP) and DVB which favors the adsorption of hydrophilic components in NOM. The two fractionation methods of DAX-8 + XAD-4 and DAX-8 + NDAM were applied to fractionate NOM, and the obtained fractions were characterized via fluorescence spectra, UV spectra, acid-base titration, the partition coefficients of aqueous two-phase systems(ATPs), and 1H nuclear magnetic resonance (1H-NMR). The results showed that the transphilic fractions separated by XAD-4 accounted for 11.09% of NOM, while the proportion increased to 20.33% with the method of NDAM fractionation. Besides, the hydrophilic components enriched by NDAM not only have more π-conjugated systems and more aromatic structure but also contain more oxygen-containing and nitrogen-containing functional groups. In addition, the hydrophilic fractions separated by NDAM contained more DBP precursors. The NDAM separates more NOM which can produce bromine-containing DBPs into HPIA, and the DBP productivity of HPIN is significantly higher than that of XAD-4. In general, the NOM fractionation method proposed in this study utilizing NDAM resin could fractionate the hydrophilic fractions in NOM more thoroughly, showing application potential in the analysis and control of DBPs formed from NOM.

Facile green preparation of single- and two-component modified activated carbon fibers for efficient trace heavy metals removal from drinking water

Trace heavy metals exist in drinking water, having great adverse effects on human health and making it a huge challenge to remove. Herein, novel materials have been prepared by a simple and green method using single- (polydopamine (PDA) or 2,3-dimercaptopropanesulfonic sodium (DMPS)) (PDA-OACF or DMPS-OACF) and two-component (PDA and DMPS) (DMPS-PDA-OACF) functionalized activated carbon fibers pretreated by hydrogen peroxide for the removal of trace heavy metals. The as-prepared DMPS-OACF (7.5,20) under DMPS addition of 7.5 mg and sonication time of 20 min retained large specific surface area, micro-mesoporous structure and rich functional groups and showed better adsorption performance for trace lead and mercury. It also exhibited wide applicable ranges of pH (3.50-10.50) and concentration (50-1136 μg L^-1), rapid adsorption kinetics, and excellently selective removal performance for trace lead. The maximum lead adsorption capacity reached 16.03 mg g^-1 when the effluent lead concentration met World Health Organization (WHO) standard and the adsorbent can be regenerated by EDTA solution. The fitting results of adsorption kinetics and isotherm models revealed that the lead adsorption process was multi-site adsorption on heterogeneous surfaces and chemical adsorption. The excellent adsorption properties for trace heavy metals were attributed that the sulfur/oxygen/nitrogen-containing functional groups boosted diffusion and adsorption by electrostatic attraction and coordination, suggesting that DMPS-OACF (7.5,20) has great application potential in the removal of trace heavy metals.

Efficient Iodine Removal by Porous Biochar-Confined Nano-Cu2O/Cu0: Rapid and Selective Adsorption of Iodide and Iodate Ions

Iodine is a nuclide of crucial concern in radioactive waste management. Nanomaterials selectively adsorb iodine from water; however, the efficient application of nanomaterials in engineering still needs to be developed for radioactive wastewater deiodination. Artemia egg shells possess large surface groups and connecting pores, providing a new biomaterial to remove contaminants. Based on the Artemia egg shell-derived biochar (AES biochar) and in situ precipitation and reduction of cuprous, we synthesized a novel nanocomposite, namely porous biochar-confined nano-Cu₂O/Cu⁰ (C-Cu). The characterization of C-Cu confirmed that the nano-Cu₂O/Cu⁰ was dispersed in the pores of AES biochar, serving in the efficient and selective adsorption of iodide and iodate ions from water. The iodide ion removal by C-Cu when equilibrated for 40 min exhibited high removal efficiency over the wide pH range of 4 to 10. Remarkable selectivity towards both iodide and iodate ions of C-Cu was permitted against competing anions (Cl^-/NO₃^-/SO₄^2-) at high concentrations. The applicability of C-Cu was demonstrated by a packed column test with treated effluents of 1279 BV. The rapid and selective removal of iodide and iodate ions from water is attributed to nanoparticles confined on the AES biochar and pore-facilitated mass transfer. Combining the advantages of the porous biochar and nano-Cu₂O/Cu⁰, the use of C-Cu offers a promising method of iodine removal from water in engineering applications.

Converting Chrysotile Nanotubes into Magnesium Oxide and Hydroxide Using Lanthanum Oxycarbonate Hybridization and Alkaline Treatment for Efficient Phosphate Adsorption

Magnesium oxide and hydroxide nanomaterials comprise a class of promising advanced functional metal nanomaterials whose use in environmental and material applications is increasing. Several strategies to synthesize these nanomaterials have been described but are unsustainable and uneconomic. This work reports on a processing strategy that turns natural magnesium-rich chrysotile into magnesium oxide and hydroxide nanoparticles via nanoparticle hybridization and an alkaline process while enabling La-based nanoparticles to coat the chrysotile nanotube surfaces. The adsorbent's resulting hybrid nanostructure had an outstanding capacity for phosphate uptake (135.2 mg P g^-1) and enhanced regeneration performance. Furthermore, the adsorbent featured wide applicability with respect to the coexistence of competitive anions and a broad range of pH conditions, and its high-performance phosphate removal from sewage effluent was also demonstrated. Spectroscopic and microscopic analyses revealed the scavenging ability of phosphate by the La-based and Mg-based nanoparticles and the multiple capture mechanisms involved, including surface complexation and ion exchange. This proposed approach expands chrysotile's potential use as a magnesium-rich nanomaterial and harbors great promise for the removal of pollutants in a variety of real-world settings.

Recyclable structured toxic industrial nickel-containing sludge for efficient anionic contaminant adsorption

Safe, efficient, and simultaneous treatment of toxic industrial sludge and anionic contaminant crisis in one route still remains a persistent global challenge. Herein, we proposed a facile waste-control-waste conceptual design strategy to develop low-cost and high-performance sludge-based adsorbent for not only recycling of toxic waste nickel-containing sludge (NCS) but for the efficient removal of anionic contaminants in wastewater. The as-designed Ni-Al layered double oxides/calcined NCS (Ni-Al LDOs/CNCS) (216.96 m²/g, 0.44 cm³/g) with hierarchical porous structure possessed a larger specific surface area and well-developed porosity compared with raw NCS (60.52 m²/g, 0.26 cm³/g). It was proved that a higher hydrothermal temperature (180 °C) and a longer hydrothermal time (24 h) both promote the in situ assembly of LDHs nanosheets on CNCS surface. Significantly, the sludge-based adsorbent displayed high adsorption capacity towards five representative anions including F^- (~ 31.1 mg/g), SO₄^2- (~ 37.7 mg/g), NO₃^- (~ 21.8 mg/g), Cl^- (~ 28.0 mg/g), and H₂PO₄^- (~ 35.8 mg/g). Furthermore, the adsorbent maintained desirable adsorption capacity even after 6 adsorption/desorption cycles. Therefore, this study could be potentially extended toward design of other industrial waste sludge-derived high value-added advanced materials and for wastewater treatment applications.

Metal-based adsorbents for water eutrophication remediation: A review of performances and mechanisms

Controlling eutrophication requires satisfying stringent phosphorus concentration standards. Metal-based adsorbents can effectively remove excess phosphorus from water bodies and achieve ultra-low phosphorus concentration control for wastewater. This review focuses on the material properties and phosphorus removal mechanism of metal-based adsorbents (Fe, Al, Ca, Mg, La). There are significant differences in physical and chemical properties of different metal materials, due to the different preparation methods and synthetic materials. The main factors affecting phosphorus removal performance include particle size, crystal structure and pH_PZC. Smaller particle size, more disordered crystal structure and higher pH_PZC are more favorable for phosphorus removal. The main mechanism of phosphorus removal by metal-based adsorbents is ligand exchange, which makes it exhibit excellent adsorption capacity, fast kinetics and well selectivity for phosphate. In addition, in order to improve the phosphorus removal performance, the surface properties of the adsorbent (e.g., surface charge, surface area, and functional groups) can be effectively improved by dispersion of biochar carriers or combination of multiple metal materials. In further studies, we should improve the absorption capacity of the adsorbent under high pH conditions and the resistance to coexisting ion interference. Finally, in order to ensure the effective application of metal-based adsorbents in the phosphorus removal field, experimental scale should be expanded in future work to suit the actual water body conditions.

Remediation of PO43− in Water Using Biodegradable Materials Embedded with Lanthanum Oxide Nanoparticles

Eutrophication, a process in which algae grow inordinately, adversely affects aqueous fauna. Phosphorous at levels above 0.1 mg/L is adequate to cause eutrophication. In this study, we aimed to reduce the amount of PO43− in water using biodegradable and ecofriendly sorbents. Lanthanum oxide nanoparticles were doped in agar and cellulose sponge to produce two new sorbents, agar–La and sponge–La, respectively. Both sorbents showed high efficacy in remediating up to 10 mg/L PO43− in water. Sponge–La was found to be more proficient in terms of adsorption than agar–La because it required just 1 h to achieve 80% adsorption when the initial concentration of PO43− was 10 mg/L. Sponge–La was effective at pH levels ranging from 4 to 8, with a removal rate of 80–100%. Although agar–La displayed a slow sorption process, it presented a high adsorption capacity (156 mg/g); moreover, the cake-shaped agar–La could be easily manufactured and separated from an aqueous matrix or any water-based solutions. These two sorbents could effectively remove high concentrations of PO43−, and their preparation requires a simple step. Agar–La was easier to manufacture, whereas the adsorption process using sponge–La was more rapid. In addition, both sorbents can be easily separated from the matrix after sorption.

High efficiency and selective removal of Cu(Ⅱ) via regulating the pore size of graphene oxide/montmorillonite composite aerogel

In this study, based on the differences in the coordination configurations of various alkaline earth metal ions (Ca(Ⅱ) and Sr(Ⅱ)) and sodium alginate (SA), the aerogel is functionalized with controllable slit-shaped pores structure, contributing by nanosheet stacking impact of graphene oxide (GO) and montmorillonite (MMT), which is able to selectively remove plane hydrate copper ions in complex wastewater systems. Sr-G/M is endowed with denser slit-shaped pores and could achieve more efficient selective removal of Cu(Ⅱ), together with a best removal efficiency of 97.1%, proving by systematic adsorption tests. The selectivity tests show that Sr-G/M exhibits preferential adsorption for Cu(Ⅱ) with a distribution coefficient of 41.85 L g^-1. Furthermore, Sr-G/M has excellent regeneration performance to be 86.4% after 8 recycles. Considering its cost-effectiveness, eco-friendliness, easy preparation and efficient selective removal performance, Sr-G/M holds great promise in selective removal of Cu(Ⅱ) from complex wastewater systems.