Phosphate Removal Performance Research Articles

Enhanced phosphate removal and antibacterial action using hierarchically structured La MOF-20%-C adsorbents and filter membranes

To enhance the phosphate removal performance, a porous material (La MOF-20 %-C) was prepared by selectively removing the thermally unstable NH2-BDC ligand from a lanthanum dual organic ligand MOF through pyrolysis. This innovative approach equips La-MOF-20 %-C with dual functionalities: high phosphate adsorption capacity and robust antibacterial effects. The adsorbent showcased a remarkable phosphate adsorption capacity of 97.24 mg P/g and reached equilibrium within 90 min. The material exhibits good anti-interference capability, and the presence of multiple coexisting ions does not affect its adsorption performance. Additionally, it can be used over a wide pH range (3.0–8.0) and has good reusability. Mechanistic studies indicated that electrostatic attraction and ligand exchange were the primary mechanisms for phosphate adsorption. Moreover, La MOF-20 %-C effectively inhibited the metabolic activities of Escherichia coli and Staphylococcus aureus through phosphorus starvation and electrostatic attraction, demonstrating significant antibacterial properties. Importantly, the fabrication of this material into a filter membrane enabled the successful treatment of 16.8 L of actual wastewater, achieving an overall phosphate removal rate of over 85 %, and effectively removing total bacteria. These findings highlight La MOF-20 %-C as a highly promising material with dual functionality for phosphate removal and bacterial inhibition.

Monodispersed and Organic Amine Modified La(OH)3 Nanocrystals for Superior Advanced Phosphate Removal.

Advanced phosphate removal is critical for alleviating the serious and widespread aquatic eutrophication, strongly depending on the development of superior adsorption materials to overcome low chemical affinity and sluggish mass transfer at low phosphate concentrations. Herein, the first synthesis of monodispersed and organic amine modifiedlanthanum hydroxide nanocrystals (OA-La(OH)3) for advanced phosphate removal by modulating inner Helmholtz plane (IHP), is reported. These OA-La(OH)3 nanocrystals with positively charged surfaces and abundant exposed La sites exhibitspecific affinity toward phosphate, delivering a maximum adsorption capacity of 168mg Pg⁻1 and a wide pH adaptability from 3.0 to 11.0, as well as a robust anti-interference performance, far surpassing those of documented phosphate removal materials. The superior phosphate removal performance of OA-La(OH)3 is attributed to its protonated organic amine in IHP, which enhances the electrostatic attraction around the adsorbent-solution interface. Impressively, OA-La(OH)3 can treat ≈5 000 and ≈3 200 bed volumes of simulated and real phosphate-containing wastewater to below extremely strict standard (0.1mgL⁻1) in a fixed-bed adsorption mode, exhibiting great potential for advanced phosphate removal. This study offers a facile modification strategy to improve phosphate removal performance of nanoscale adsorbents, and sheds light on the structure-reactivity relationship of La-based materials.

Zero-valent iron in phosphate removal: Unraveling the role of particle size and dissolved oxygen

The effect of particle size and dissolved oxygen (DO) on zero-valent iron (ZVI) oxidation needs further study to propose strategies for improving phosphate (P) removal performance. In this study, batch and column experiments were conducted to investigate P removal by ZVI with five different particle sizes under aerobic and anaerobic conditions. The oxidation status of ZVI before and after the reaction was characterized. Under aerobic conditions, as ZVI size increased, the P removal rate initially increased and then decreased, while the difference in P removal was not obvious under anaerobic conditions. Furthermore, the P removal rate exhibited a significant positive correlation with the degree of ZVI oxidation (R2 = 0.877, p = 0.008), highlighting its pivotal role in P removal. The ZVI size and DO on ZVI oxidation primarily affect the types and quantities of iron corrosion products (FeCPs). Under aerobic conditions, the ZVI with small particle sizes (ZVIsps) (50 nm, 500 nm, and 5 μm) tended to form passivation layers composed of amorphous iron oxide (ap-FexOy) and FePO4, limiting ZVI oxidation and resulting in lower P removal rates (17.6%). Conversely, in situations with less passivation, amorphous iron hydroxides (ap-FexOHy) play a dominant role in the P removal process. The 50 μm ZVI eventually generated lepidocrocite (γ-FeOOH) under aerobic conditions, this sufficient oxidation was also the reason for its high P removal rate. Therefore, future research and applications of ZVI materials in P removal should concentrate on enhancing ZVI corrosion and regulating the formation of suitable FeCPs.

Oxalate modification enabled advanced phosphate removal of nZVI: In Situ formed surface ternary complex and altered multi-stage adsorption process

Nano zero-valent iron (nZVI) is a promising phosphate adsorbent for advanced phosphate removal. However, the rapid passivation of nZVI and the low activity of adsorption sites seriously limit its phosphate removal performance, accounting for its inapplicability to meet the emission criteria of 0.1 mg P/L phosphate. In this study, we report that the oxalate modification can inhibit the passivation of nZVI and alter the multi-stage phosphate adsorption mechanism by changing the adsorption sites. As expected, the stronger anti-passivation ability of oxalate modified nZVI (OX-nZVI) strongly favored its phosphate adsorption. Interestingly, the oxalate modification endowed the surface Fe(III) sites with the lowest chemisorption energy and the fastest phosphate adsorption ability than the other adsorption sites, by in situ forming a Fe(III)-phosphate-oxalate ternary complex, therefore enabling an advanced phosphate removal process. At an initial phosphate concentration of 1.00 mg P/L, pH of 6.0 and a dosage of 0.3 g/L of adsorbents, OX-nZVI exhibited faster phosphate removal rate (0.11 g/mg/min) and lower residual phosphate level (0.02 mg P/L) than nZVI (0.055 g/mg/min and 0.19 mg P/L). This study sheds light on the importance of site manipulation in the development of high-performance adsorbents, and offers a facile surface modification strategy to prepare superior iron-based materials for advanced phosphate removal.

Assessing the effectiveness of low-cost materials to act as filter media for phosphate sorption

In this research, an assessment was conducted for several materials to examine their efficiency for sorption phosphate and their potential use as filter media. This work focuses on seeking materials that can achieve high, rapid, and robust phosphate retention. To assess the phosphate removal efficiency, batch-mode testing was conducted. The capability of the selected materials for effectively removal the phosphate is largely influenced by their inherent properties. Therefore, this research determines the effectiveness of the material by examining its physical and chemical characteristics. The selection method for these materials was guided by the understanding that the sorbents that have the most effective behavior for phosphate tend to contain easily soluble Ca/Mg compounds or Fe/Al hydroxides. The findings of the batch experiments demonstrated that material such as Bio ash (Bio-A) exhibited superior phosphate removal performance throughout the entire duration of the experiments. In contrast, materials calcium carbonate (C-C) and conventional silica (C-S) displayed relatively poor removal performance compared to Bio-A.

Unlocking Bimetallic Active Centers via Heterostructure Engineering for Exceptional Phosphate Electrosorption: Internal Electric Field-Induced Electronic Structure Reconstruction.

Development of electrode materials exhibiting exceptional phosphate removal performance represents a promising strategy to mitigate eutrophication and meet ever-stricter stringent emission standards. Herein, we precisely designed a novel LaCeOx heterostructure-decorated hierarchical carbon composite (L8C2PC) for high-efficiency phosphate electrosorption. This approach establishes an internal electric field within the LaCeOx heterostructure, where the electrons transfer from Ce atoms to neighboring La atoms through superexchange interactions in La-O-Ce coordination units. The modulatory heterostructure endows a positive shift of the d band of La sites and the increase of electron density at Fermi level, promoting stronger orbital overlap and binding interactions. The introduction of oxygen vacancies during the in situ nucleation process reduces the kinetic barrier for phosphate-ion migration and supplies additional active centers. Moreover, the hierarchical carbon framework ensures electrical double-layer capacitance for phosphate storage and interconnected ion migration channels. Such synergistically multiple active centers grant the L8C2PC electrode with high-efficiency record in phosphate electrosorption. As expected, the L8C2PC electrode demonstrates the highest removal capability among the reported electrode materials with a saturation capacity of 401.31 mg P g-1 and a dynamic capacity of 91.83 mg P g-1 at 1.2 V. This electrochemical system also performs well in the dephosphorization in natural water samples with low concentration that enable effluent concentration to meet the first-class discharge standard for China (0.5 mg P L-1). This study advances efficient dephosphorization techniques to a new level and offers a deep understanding of the internal electric field that regulates metal orbitals and electron densities in heterostructure engineering.

Investigation of filtration performance and phosphorus removal in an electric field controlled dynamic membrane bioreactor

Dynamic membrane bioreactor (DMBR) offers several advantages over traditional membrane bioreactor, including cheaper costs, less resistance, and easier cleaning. Membrane fouling and poor phosphate removal performance restrict the application of DMBR. To address it, this study creatively combined electric field with DMBR and investigated the mechanisms. The results showed that applying an electric field significantly decreased membrane fouling rate in electric dynamic membrane bioreactor with Ti anode (E-DMBR-Ti). The median membrane fouling rate of E-DMBR-Ti was 2.28 kPa/h, which was 48.99 % lower than that of control group (4.47 kPa/h) during stable operation period. However, hydrogen bubbles formed on the cathode blocked membrane during membrane formation period. The enrichment of electroactive and denitrifying microorganisms (e.g., Lactococcus, Hydrogenophaga) in E-DMBR-Ti, which consumed electrons that would flow to the hydrogen evolution reaction, alleviated the negative impact. To address the issue of poor phosphorus removal efficiency of DMBR, based on the previous research, we replaced the titanium mesh of the anode with aluminum plates, and innovatively using the electrocoagulation technology which named E-DMBR-Al. At 2.4 A/m2 current density, E-DMBR-Al showed the highest phosphorus removal efficiency, with a median of 94.69 %, which was 37.69 % higher than that of DMBR. Furthermore, the enrichment of electroactive microorganisms (e.g., Lactococcus) and polyphosphate-accumulating organisms (e.g., unclassified_f__Comamonadaceae) on membrane contributed to the excellent phosphorus removal performance of E-DMBR-Al.

Phosphorus removal with zero-valent iron: Fixed-bed experiments with long-term monitoring and solid analysis

Zero Valent Iron (ZVI) is considered a good media for contaminant removal in wastewater. Through batches and fixed-bed experiments, phosphate (P) removal performances of iron-based materials were studied. Three iron-based materials, with various grain sizes and compositions, were selected to fill columns in a reactive mix with sand, with two ratios (1 % and 10 % iron). After 300 days, the columns were dismantled and solid analyses performed on the remaining media. Over 50 % P retention was observed for the 1 % ZVI/sand ratio reactors for longer than 6 months. For the 10 % ratio, better performances were attained over a longer lifetime (above 70 % for 7 months). The P distribution was heterogeneous along the column since the activation of the layers were gradually influenced by both oxygen and P concentrations. Solid analyses showed that P was mostly bound to amorphous iron oxides (55 %), with a small percentage being linked to crystalline iron byproducts (10 %). >10 % of P was retained by calcium, highlighting its contribution to P scavenging. In considering the influence of these major parameters, an overview of P removal mechanisms through a continuous upflow fixed-bed was then proposed, that could be helpful for future P treatment reactor's design.

Green water-etching synthesized La-MIL-101(Fe)-NH2@SiO2 yolk-shell nanocomposites with superior pH stability for efficient and selective phosphorus recovery

Although MIL-101(Fe) has a homogeneous distribution of active metal sites, the relatively low stability of its coordination bonds limits its potential for application, especially in harsh environments. Here, a novel lanthanum-doped MIL-101(Fe)-NH2@mesoporous SiO2 yolk-shell (LMFN-YS) material, synthesized by green water-etching, has effectively improved the adsorption capacity and stability of MIL-101(Fe)-NH2. Compared to traditional acid-base etching methods, water etching offered a more co-friendly and cost-effective approach to producing yolk-shell structures. Due to the mesoporous protective shell of mesoporous SiO2 and more exposed active sites, the yolk-shell materials showed a faster adsorption rate (30 min) and a larger uptake capacity (240.0 mg P/g) than those of MIL-101. The material also exhibited broad range of pH stability from 2 to 10 and displayed good cyclic regeneration ability, with a removal efficiency of 75.9 % after three cycles. Additionally, it demonstrated excellent selectivity towards various coexisting anions such as Cl−, NO3−, SO42−, CO32− and HCO3− at diverse ionic strengths ranging from 0.001 to 1 M. The superior performance of L1MFN-YS (yolk-shell materials of La: Fe = 1:1) was attributed to a combination of factors, including ligand exchange between La(Fe)-OH and phosphates, Lewis acid-base interaction and electrostatic attraction. Additionally, high phosphate removal performance was observed in the real petrochemical wastewater (initial concentrations of 5.48 mg P/g) with a residual effluent concentration of 0.05 mg P/L, which was below the A-level standard of phosphate effluent in China (0.5 mg/L). This work provides a green method for preparing yolk-shell materials with improved ability to treat phosphate wastewater.

Phosphate removal mechanism of a novel magnesium slag-modified coal gasification coarse slag adsorbent

We used magnesium slag (MS) as a calcium source for modifying coal gasification coarse slag (CGCS) in the presence of NaOH to prepare a novel phosphate adsorbent (MS-CGCS). Ca2SiO4 in MS reacts with NaOH during the high-temperature synthesis process, with sodium displacing a part of the calcium content in Ca2SiO4 and entering the mineral lattice to form Na2CaSiO4. Hydroxide ions reacted with calcium in Ca2SiO4 to generate Ca(OH)2 and decomposed into CaO at a high temperature. The two newly formed species participated in the phosphate removal. The MS-CGCS adsorbent showed good phosphate removal performance over a wide pH range, with a maximum phosphate adsorption capacity of 50.14mg/g, which was significantly higher than that of other reported adsorbents. The Langmuir and pseudo-second-order models described the adsorption process well, indicating it being a monolayer and chemisorption process. The main mechanisms of phosphate removal are as follows: electrostatic interaction between the positively charged MS-CGCS and negatively charged phosphate ions; the inner-sphere complexation of oxides of metal, such as magnesium, aluminum, and calcium, with phosphate ions; and the precipitation of phosphate ions with calcium ions. Precipitation contributes to ~ 32% of the phosphate removal. This study provides a new method for the development of phosphate adsorbents while recycling CGCS and MS.

Preparation and Characterization of an Invasive Plant-Derived Biochar-Supported Nano-Sized Lanthanum Composite and Its Application in Phosphate Capture from Aqueous Media.

Invasive plants pose a great threat to natural ecosystems owing to their rapid propagation and spreading ability in nature. Herein, a typical invasive plant, Solidago canadensis, was chosen as a novel feedstock for the preparation of nano-sized lanthanum-loaded S. canadensis-derived biochar (SCBC-La), and its adsorption performance for phosphate removal was evaluated by batch adsorption experiment. The composite was characterized by multiple techniques. Effects of parameters, such as the initial concentration of phosphate, time, pH, coexisting ions, and ionic strength, were studied on the phosphate removal. Adsorption kinetics and isotherms showed that SCBC-La shows a faster adsorption rate at a low concentration and SCBC-La exhibits good La utilization efficiency than some of the reported La-modified adsorbents. Phosphate can be effectively removed over a relatively wide pH of 3-9 because of the high pH pzc of SCBC-La. Furthermore, the SCBC-La shows a strong anti-interference capability in terms of pH value, coexisting ions, and ionic strength, exhibiting a highly selective capacity for phosphate removal. Additionally, Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) measurements reveal that hydroxyl groups on the surface of SCBC-La were replaced by phosphate and manifest the reversible transformation between La(OH)3 and LaPO4. Considering its high adsorption capacity and excellent selectivity, SCBC-La is a promising material for preventing eutrophication. This work gives a new method of pollution control with waste treatment since the invasive plant (S. canadensis) is converted into biochar-based nanocomposite for effective removal of phosphate to mitigate eutrophication.

Optimized Ca-Al-La modified biochar with rapid and efficient phosphate removal performance and excellent pH stability

Biochar-based adsorbents for phosphate removal from wastewater has gained increasing attention and achieved significant progress. However, there is still much room for the enhancement on adsorption performance in terms of removal rate, adsorption capacity and pH application range. Herein, novel Ca-Al-La modified biochar adsorbents in this study were synthesized for enhancing phosphate adsorption in wastewater. The synthesis parameters of adsorbents were optimized by using the response surface methodology (RSM). The Ca-Al-La modified biochar adsorbent synthesized under the optimal conditions (CAL-MBC) exhibited superior adsorption capability towards phosphate. Specifically, CAL-MBC achieved a rapid removal rate to reach the adsorption equilibrium within 1 h, a maximum phosphate adsorption capacity of 152.9 mg/g, and excellent pH stability within a broad pH range of 3.0–11.0. The adsorption mechanisms involving electrostatic interaction, precipitation and inner-sphere complexation via ligand exchange were responsible for the excellent adsorption performance of phosphate on CAL-MBC. This study verifies CAL-MBC as a promising metal modified biochar adsorbent to enhance phosphate removal from wastewater.

Advanced removal of phosphate from water by a novel lanthanum manganese oxide: Performance and mechanism

A novel lanthanum manganese oxide (La0.96Mn0.96O3, LMO) was synthesized for advanced phosphate removal to alleviate water eutrophication process. The adsorbent had a specific surface area of 18.51 m2/g with pH at point of zero charge of 6.6; exhibited excellent phosphate adsorption capacity of 168.4mg/g; performed well in a wide pH range from 3 to 10. The phosphate removal was not interfered by coexisting ions. The adsorbent remained 94.8% of its initial adsorption efficiency after reused for four times. Phosphate adsorption process conformed to pseudo-second-order model (R2=0.992) and Langmuir model (R2=0.935). Ligand exchange and electrostatic interaction played important roles in phosphate removal. In addition, the actual sewage secondary effluent was used to further verify the phosphate removal performance of LMO. For practical water treatment, the LMO showed high phosphate removal efficiency of 83.4% and low residual P of 0.1mg/L. LMO is a potential candidate for low-concentration phosphate removal in real water environment.

Phosphate removal performance and mechanism of magnesium–lanthanum-modified coal gasification coarse slag

Herein we present a novel coal gasification coarse slag (CGCS)-loaded magnesium–lanthanum bimetallic phosphate remover. The as-prepared composite (denoted ML2-CGCS) with a magnesium (Mg): lanthanum (La) molar ratio of 1:2 was found to be the best phosphate remover. The modification of CGCS with magnesium instead of lanthanum not only maintains a good phosphate adsorption capacity but also greatly reduces the cost of lanthanum-modified materials; this can save 4601 yuan per ton (in RMB). The maximum phosphate adsorption capacity was 39.22 mg/g, and 35 mg/L phosphate was nearly completely adsorbed within 180 min, exhibiting good phosphate removal capabilities. The effects of humic acid and anions demonstrated that ML2-CGCS has a good selectivity for phosphate removal. A metal leaching study showed that loading Mg–La on CGCS can reduce the lanthanum release problem of Mg–La hydroxides. Saturated ML2-CGCS can be reclaimed at least four times, and can continuously treat more than 1026 bed volumes of actual wastewater. The phosphate removal mechanism involves precipitation, electrostatic attraction, and the inner-sphere complexation. This study revealed that ML2-CGCS exhibits good selectivity, phosphate removal efficiency, and reproducibility, and it can be used to treat actual phosphate wastewater and thereby recover phosphate. This study provides a new method for the development of phosphate adsorbents while recycling CGCS.

Rational design of the nanocomposite by in-situ sub-10 nm La(OH)3 formation for selective phosphorus removal in waters

Phosphate removal by nanocomposite is a promising approach in water remediation. But it is still challenged by the small size nanoparticles formation and kinetic diffusion under the nanopore confinement. Herein, we report a different strategy, which relies on the deposition of nano-La(OH)3 particles inside the porous biomass Artemia Cyst-shells matrix. The charged amino acid components of matrix drivers for the in-situ growth of rod-like nano-La(OH)3 with size below 10 nm, while the broad-porous skeleton structures enable and accelerate the accessibility of trace phosphate to nano-La(OH)3 sorption sites available, resulting in the efficient and fast phosphate removal performance. This nanocomposite exhibited excellent adsorption capacity as high as 180.5 mg/g, which is beyond of most adsorbents by recent-ten-year survey. It also revealed superior selectivity against various competing ions with a distribution coefficient (Kd) up to ∼ 34000 mL/g, exceeding commercial ion-exchange resin by 15 times and outdoing 10 times the performance of well-known Fe based nanocomposites Lewatit FO36. An outstanding treatment capacity of 10980 L/kg under the continuous operation and the satisfactory regeneration property (> 95 %) further proves its applicability. This technology provides a new perspective approach for nanocomposite design and wastewater determination. It is also promising alleviating problems of trace phosphate deep purification in drinking water and wastewater medium.

Enhancing phosphate removal performance in water using La–Ca/Fe–LDH: La loading alleviates ineffective stacking of laminates and increases the number of active adsorption sites

Increasing the number of adsorption sites in layered bimetallic hydroxide (LDH), which is frequently used for phosphate removal in water, is a crucial step in enhancing phosphate adsorption. In this study, we investigate whether lanthanum (La) metal loading can improve the phosphate adsorption capacity of LDH. Based on Ca/Fe–LDH prepared through coprecipitation, a La–Ca/Fe–LDH composite is fabricated by La loading through impregnation. The adsorption capacity of La–Ca/Fe–LDH is 11.4% higher than that of Ca/Fe–LDH. The magnitude of adsorption and accelerated rate of adsorption of La–Ca/Fe–LDH satisfy the quasi-second-order kinetic and Langmuir isothermal equations. When comparing La–Ca/Fe–LDH to Ca/Fe–LDH, the adsorption capacity increased by 3.3%–328.39% in the pH range of 3–11; additionally, the resistance to pH influence and coexisting ion interference was considerably enhanced. However, under the coexistence of Cl−, NO3−, CO32−, SO42−, and F−, the adsorption capacity increased by 20.59%–27.6%. After three cycles of desorption, the phosphate removal abilit till increased by 11%, and the magnetic property was suitable for separation. The improvement of La–Ca/Fe–LDH adsorption capacity is attributed to the relief of ineffective stacking of LDH laminates and increased number of adsorption sites. The primary causes of adsorption are ion exchange, electrostatic attraction, and ligand exchange. In this study, a novel technique for enhancing LDH adsorption capability is proposed. This technique has numerous potential applications related to adsorbents in water treatment.

Sludge-derived biopolymers for in-situ synthesis of magnetic ALE-Fe-Zr composites for phosphate removal

Resource recovery of excess sludge has been important to achieve the sustainability of wastewater treatment, thereinto alginate-like exopolysaccharides (ALE) are considered as valuable bio-products with broad application potential. In this study, ALE were firstly employed as the biotemplates for fabricating controllable nanostructures to remove phosphate, the binding ability of ALE to metal ions (Fe3+ and Zr4+) effectively confined the in-situ growth of metal nanoparticles under calcination. The ALE-metal composites with a Fe/Zr molar ratio of 5 (ALE-Fe5-Zr) showed high phosphate removal efficiencies of 96.1% and 98.1% at 1 and 10 mg-P L−1, respectively, which was largely attributed to its homogeneity, high specific surface area, and mesoporous structure. The phosphate adsorption by ALE-Fe5-Zr composites fitted well with pseudo-second-order kinetics and Freundlich isotherm model. Meanwhile, the composites achieved stable phosphate removal performance under a wide pH range of 4–8, and showed a high selectivity to phosphate in the presence of Cl−, SO42−, NO3−, HCO3−, and F−. Moreover, ALE-Fe5-Zr composites maintained the favorable performance in treating real wastewater containing 2.47 mg-P L−1, and the phosphate concentration reached target discharge limit of 0.5 mg-P L−1 within 20 min. The reusability tests demonstrated that ALE-Fe5-Zr composites could be recovered by magnetic separation and kept 83.8% of original adsorption capacity after five cycles. The possible adsorption mechanisms involving electrostatic interaction, ligand exchange, and Lewis acid-base interaction were supported by batch experiments, FTIR, and XPS analyses. This work provided a facile route for synthesizing ALE-mediated magnetic composites with high efficiency, selectivity, and stability for phosphate removal.

Novel composite in situ obtained from coal gasification coarse slag and its mechanism of removing phosphate

A novel low-cost hematite–silicon mesoporous composite (HSMC) was synthesized in situ from coal gasification coarse slag (CGCS) via acid modification and its potential for phosphate removal from wastewater was studied. Calcium, aluminum and iron in CGCS were activated by hydrochloric acid, and formed crystalline hematite on the quartz and silicates substrates. Compared with traditional methods of preparing hematite, this in-situ preparation method effectively utilized the iron in CGCS instead of requiring added iron salts, which is highly cost-effective. The specific surface area increased from 4 m2/g for CGCS to 67 m2/g for HSMC, greatly enhancing the phosphate removal ability of HSMC. The maximum adsorption capacity of HSMC for phosphate was 28.62 mg/g, which is more than 28 times higher than that of CGCS. The HSMC had a high point of zero charge (pHPZC) of 7.5, providing good phosphate removal performance over a wide pH range. The phosphate removal mechanism of HSMC mainly involves ligand exchange induced by the large number of hydroxyl groups, inner-sphere complexation induced by the presence of major metal (hydr)oxides, the precipitation of calcium and aluminum with phosphate groups, and some electrostatic adsorption induced by the positively charged surface. The contribution of precipitation to the phosphate removal ability was approximately 27 %. This study provides a new method for the development of phosphate adsorbents while recycling CGCS.

Mechanochemically activated microscale zero-valent iron with carboxymethylcellulose for efficient sequestration of phosphate in aqueous solution

This study modified microscale zero valent iron (mZVI) using hydrophilic sodium carboxymethyl cellulose (CMC) via mechanical ball milling method, which was donated as CMC-mZVI, and compared the phosphate removal performance of mZVI and CMC-mZVI. Characterization results of X-ray powder diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), EDS-mapping images of CMC-mZVI demonstrated that the dominant crystalline structure of mZVI did not alter significantly after the ball-milling process and CMC could be adsorbed on the surface of mZVI. Further phosphate (PO43-) removal experimental results revealed that the PO43- removal percentage of CMC-mZVI within 360 min was 99.99 %, which was much higher than that of mZVI (75.23 %). Subsequently, this study analyzed the concentration of ferrous ions and total iron ions dissolved by mZVI and CMC-mZVI, compared the high resolution X-ray photoelectron spectroscopy (HR-XPS) of mZVI and CMC-mZVI before and after the phosphate removal, and characterized the affinity of CMC-mZVI (or mZVI) to water by testing the static contact angle between CMC-mZVI (or mZVI) and water. The above results suggested that the existence of CMC on the surface of mZVI could promote the hydrophilic property of mZVI, resulting the enhancement of ferrous ions and total iron ions dissolution by 8 and 8.78 times than that of mZVI, and the rapid co-precipitation of phosphate. This study provided an environmentally friendly and effective method to improve the reactivity of commercial mZVI powder, and contributed to the wide application of mZVI technology in the field of environmental remediation.

Resourcing of building waste brick slags as a column packing material: Toward excellent phosphate removal performance for water treatment

Efficient phosphorus removal from wastewater is of paramount importance, however, the design of low-cost, high-performance materials for phosphorus removal is faced with a huge challenge. Herein, a waste brick slag loaded with iron oxide and lanthanum hydroxide (WB@Fe2O3-La(OH)3) has been prepared by sequential deposition of Fe2O3 and La(OH)3 nanoparticles on the surface of brick slag particles and applied to removal of phosphate from wastewater via column separation, and the maximum phosphate separation efficiency can reach 99 %. More importantly, it shows a high phosphate removal efficiency (≥90 %) over the wide range of pH 3.0–8.0, in addition to a high separation selectivity toward phosphate and high throughput during separation process. The low cost and high removal efficiency benefit from the use of building waste bricks and column separation which due to its full contact with the target. The ligand exchange and the chemical precipitation are mainly responsible for the phosphate removal by WB@Fe2O3-La(OH)3. Therefore, the prepared WB@Fe2O3-La(OH)3 particles with the high phosphate separation efficiency and column separation for phosphate removal developed has the potential to become an excellent candidate for practical application in phosphate separation and provides a reference path for building waste brick recycling.