Enhanced phosphate removal from aqueous solution using resourceable nano-CaO2/BC composite: Behaviors and mechanisms

Role of polyferric sulphate in hydration regulation of phosphogypsum-based excess-sulphate slag cement: A multiscale investigation

Current demand for waste recycling, phosphogypsum-based excess-sulphate slag cement (PESSC) as a sustainable cement prepared by solid wastes, urges enhancing its performance development based on microstructure optimisation. For the purpose of improving the performance and durability of PESSC used in normal or corrosive environments, it is deemed an efficient technique to produce iron-doped compounds with high thermodynamic stability. This paper presents a systematic study of the effect of iron modification on PESSC binders by introducing 0%-2% polyferric sulphate (PFS) from a multiscale viewpoint. XPS, 29Si and 27Al NMR, and TEM were used to characterise the nanostructure of solid particles firstly at Level I. Then, the chemical composition and phase assemblage of PESSC binders were revealed at Level II in terms of ICC, ICP, DTG-DSC, FTIR, BSE-EDS and XRD. Finally, setting time and strength development were determined at Level III. Results indicated that the soluble FeOH4- supplied by the hydrolysis of PFS promotes the generation of iron-doped ettringite with a greater length-to-diameter ratio and thermodynamic stability. Seeding effect of iron doping also promotes the production of spherical and retiform gels with a slight influence on the chemical components and polymerisation. Despite the fact that iron doping weakens the early strength of PESSC mortars, it promotes the persistent hydration rate by retarding precipitation and encapsulation of hydrates on the surface of the slag, showing excellent strength in the later stages. In view of microstructure evolution and performance development during each stage, PFS supplementation within 1.0% is considered a feasible modification of PESSC relying on the formation control of iron-doped hydrates.

Metal-doped biochar for selective recovery and reuse of phosphate from water: Modification design, removal mechanism, and reutilization strategy

Phosphorus (P) plays a crucial role in plant growth, which can provide nutrients for plants. Nonetheless, excessive phosphate can cause eutrophication of water, deterioration of aquatic environment, and even harm for human health. Therefore, adopting feasible adsorption technology to remove phosphate from water is necessary. Biochar (BC) has received wide attention for its low cost and environment-friendly properties. However, undeveloped pore structure and limited surface groups of primary BC result in poor uptake performance. Consequently, this work introduced the synthesis of pristine BC, parameters influencing phosphate removal, and corresponding mechanisms. Moreover, multifarious metal-doped BCs were summarized with related design principles. Meanwhile, mechanisms of selective phosphate adsorption by metal-doped BC were investigated deeply, and the recovery of phosphate from water, and the utilization of phosphate-loaded adsorbents in soil were critically presented. Finally, challenges and prospects for widespread applications of selective phosphate adsorption were proposed in the future.

Novel Fe/Ca oxide co-embedded coconut shell biochar for phosphorus recovery from agricultural return flows

Efficient elimination and recovery of phosphorus from agricultural return flows are crucial for effective eutrophication management and phosphorus reuse. In this study, a neutral Fe/Ca oxide co-embedded biochar (FCBC) was synthesized using calcium peroxide and ferrous chloride as precursors for phosphate recovery from agricultural return flows. FCBC possesses a highly intricate pore structure and an abundance of surface-active groups. Fe/Ca oxides were loaded onto the biochar in the form of Ca2Fe2O5, Fe2O3, and CaCO3. FCBC demonstrated a broad pH tolerance range (pH = 6-12) in the aquatic environment. The maximum saturation adsorption capacity was 53.31 mg g-1. Phosphorus removal is influenced by Ca3(PO4)2 generation, intra-particle diffusion, and electrostatic attraction. The produced FCBC showed exceptional phosphorus removal efficiency in the presence of various anions, except for wastewater with high concentrations of SO4 2-, CO3 2-, HCO3 -, and F- (>500 mg L-1). FCBC can effectively remove phosphorus from agricultural return flows and reduce the risk of the water environment. Returning it to the field can also mitigate the depletion of phosphorus resources, effectively reduce carbon emissions from farmland, improve soil fertility, and realize multiple benefits.

Treating waste with waste: adsorption behavior and mechanism of phosphate in water by modified phosphogypsum biochar

The use of green methods to treat industrial waste and waste reuse has become a key environmental issue. In order to achieve this goal, this study treated waste phosphogypsum (PG) and produced modified PG biochar to adsorb and remove phosphorus from PG leachate, so that the PG pollution problem was controlled. In this study, PG was modified with sodium carbonate (Na2CO3) to prepare a modified PG biochar that was used for the removal of phosphorus-containing wastewater. An X-ray diffraction (XRD) analysis of the modified PG revealed that the main component was calcium carbonate (CaCO3), and a suitable amount of modified PG could load calcium oxide (CaO) onto the biochar and improve its physical properties. The experimental results showed that the modified PG biochar had a maximum phosphorus adsorption capacity of 132 mg/g. A further investigation of the mechanism of adsorption revealed the importance of electrostatic attraction and chemical precipitation, and it was found that the CaO in the modified PG biochar could effectively facilitate the conversion of phosphate to hydroxylapatite (Ca5(PO4)3OH) in water. The phosphorus removal rate from leachate obtained from a landfill containing PG was 99.38% for a specific dose of the modified PG biochar. In this study, a PG pollution control technology was developed to realize the goal of replacing waste with waste.

Polysaccharide- and protein-based edible films combined with microwave technology for meat preservation

To reduce food-borne bacterial infection caused by food spoilage, developing highly efficient food packing film is still an urgent need for food preservation. Herein, microwave-assisted antibacterial nanocomposite films CaO2@PVP/EA/CMC-Na (CP/EC) were synthesized using waste eggshell as precursor, egg albumen (EA) and sodium carboxymethylcellulose (CMCNa) as matrix by casting method. The size of CaO2@PVP (CP) nanoparticles with monodisperse spherical structures was 100-240 nm. When microwave and CP nanoparticles (0.05 mg/mL) were treated for 5 min, the mortality of E. coli and S. aureus could reach >97 %. Under microwave irradiation (6 min), the bactericidal rate of 2.5 % CP/EC film against E. coli and S. aureus reached 98.6 % and 97.2 %, respectively. After adding CP nanoparticles, the highest tensile strength (TS) and elongation at break (EB) of CP/EC film reached 19.59 MPa and 583.43 %, respectively. At 18 °C, the proliferation of bacterial colonies on meat can be significantly inhibited by 2.5 % CP/EC film. Detailed characterization showed that the excellent meat preservation activity was due to the synergistic effect of dynamic effect generated by ROS and thermal effect of microwave. This study provides a promising approach for the packaging application of polysaccharide- and protein-based biomass nanocomposite antibacterial edible films.

Nano La(OH)3 modified lotus seedpod biochar: A novel solution for effective phosphorus removal from wastewater

Effective removal of phosphorus from water is crucial for controlling eutrophication. Meanwhile, the post-disposal of wetland plants is also an urgent problem that needs to be solved. In this study, seedpods of the common wetland plant lotus were used as a new raw material to prepare biochar, which were further modified by loading nano La(OH)3 particles (LBC-La). The adsorption performance of the modified biochar for phosphate was evaluated through batch adsorption and column adsorption experiments. Adsorption performance of lotus seedpod biochar was significantly improved by La(OH)3 modification, with adsorption equilibrium time shortened from 24 to 4 h and a theoretical maximum adsorption capacity increased from 19.43 to 52.23 mg/g. Moreover, LBC-La maintained a removal rate above 99% for phosphate solutions with concentrations below 20 mg/L. The LBC-La exhibited strong anti-interference ability in pH (3-9) and coexisting ion experiments, with the removal ratio remaining above 99%. The characterization analysis indicated that the main mechanism is the formation of monodentate or bidentate lanthanum phosphate complexes through inner sphere complexation. Electrostatic adsorption and ligand exchange are also the mechanisms of LBC-La adsorption of phosphate. In the dynamic adsorption experiment of simulated wastewater treatment plant effluent, the breakthrough point of the adsorption column was 1620 min, reaching exhaustion point at 6480 min, with a theoretical phosphorus saturation adsorption capacity of 6050 mg/kg. The process was well described by the Thomas and Yoon-Nelson models, which indicated that this is a surface adsorption process, without the internal participation of the adsorbent.

A cancer cell nanotherapy method based on GHz film bulk acoustic resonator and nanoscale CaO2

Sonodynamic therapy (SDT) is an emerging cancer treatment method in recent years. However, the ultrasound signal utilized for SDT is usually located at a low-frequency spectrum (<2 MHz), and in the field of SDT research, few studies have focused on the exploration and development of ultrasound frequency. Studies have shown that the GHz-level ultrasound can increase cell membrane permeability and have a negligible effect on cell vitality. Herein, we reported the study of a GHz thin film bulk acoustic resonator as an ultrasound source for synergistic treatment with nanoscale calcium peroxide (CaO2). It was discovered that this ultrasound source ultimately achieved an efficient therapeutic outcome on mouse breast cancer cell line 4T1. Such GHz-level ultrasound application in SDT is of high significance to broaden the cognition and application scope of SDT.

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.

Combining lanthanum-modified bentonite and calcium peroxide to enhance phosphorus removal from lake sediments

Lanthanum-modified bentonite (LMB) and calcium peroxide (CP) are known for their effective removal phosphorus (P) capacities. The present study aims to investigate the effects of the combined use of LMB and CP（LMB + CP）on the sediment P, dissolved organic matter (DOM) and iron (Fe) concentrations through a 90-day incubation experiment. The combined treatment showed strong removal effects on sediment P and DOM. Indeed, the SRP and DOM concentrations in the 0-10 cm sediment layer decreased following the combined application of LMB and CP by 40.67 and 28.95%, respectively, compared to those of the control group (CK). In contrast, the HCl-P in the 0-5 cm sediment layer increased following the combined treatment by 13.28%. In addition, compared with the single application of LMB, the LMB + CP treatment significantly reduced the soluble Fe (Ⅱ) in the sediment pore water and promoted the oxidation of Fe. Therefore, LMB + CP can enhance the removal of internal P from sediments. The DOM removal and Fe oxidation in sediment pore waters are beneficial for enhancing the adsorption of P by LMB. On the other hand, the single and combined applications of LMB and CP increased the richness of the sediment microbial communities while exhibiting slight effects on their diversity. According to the results of this study, the combined use of LMB and oxidizing materials represents a novel method for treating lakes with high internal phosphorus and DOM loads in sediments.

Removal of phosphorus by modified bentonite:polyvinylidene fluoride membrane-study of adsorption performance and mechanism

Enhanced phosphorus management, geared towards sustainability, is imperative due to its indispensability for all life forms and its close association with water bodies' eutrophication, primarily stemming from anthropogenic activities. In response to this concern, innovative technologies rooted in the circular economy are emerging, to remove and recover this vital nutrient to global food production. This research undertakes an evaluation of the dead-end filtration performance of a mixed matrix membrane composed of modified bentonite (MB) and polyvinylidene fluoride (PVDF) for efficient phosphorus removal from water media. The MB:PVDF membrane exhibited higher permeability and surface roughness compared to the pristine membrane, showcasing an adsorption capacity (Q) of 23.2 mgP·m-2. Increasing the adsorbent concentration resulted in a higher removal capacity (from 16.9 to 23.2 mgP·m-2) and increased solution flux (from 0.5 to 16.5 L·m-2·h-1) through the membrane. The initial phosphorus concentration demonstrates a positive correlation with the adsorption capacity of the material, while the system pressure positively influences the observed flux. Conversely, the presence of humic acid exerts an adverse impact on both factors. Additionally, the primary mechanism involved in the adsorption process is identified as the formation of inner-sphere complexes.

Adsorption recovery of phosphorus in contaminated water by calcium modified biochar derived from spent coffee grounds

Phosphate recovery from water is essential for reducing water eutrophication and alleviating the phosphorus resource crisis. In this study, spent coffee grounds and CaCl2 were used as raw materials and a modifier, respectively, to create a novel calcium modified biochar (MBC) for removing phosphorus from water. The modified biochar (MBC) was the best at removing phosphorous when the modifier concentration was 1.5 M with theoretically maximum adsorption capacity of 70.26 mg/g. MBC also performed well in the wide pH range of 3-11 under different phosphorus concentration gradients, with phosphorus removal efficiency of more than 50 %. According to kinetic analysis, the adsorption process at low phosphorus concentrations (50-100 mg/L) can be more properly described by the pseudo-first-order model, while the pseudo-second-order model best describes the adsorption process at high concentrations (200-600 mg/L). The thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic. Characterization results revealed that surface precipitation, complexation, and ligand exchange were the dominant mechanisms of phosphorus adsorption. MBC has great potential to recover phosphorus from wastewater.

Study on the dynamic adsorption and recycling of phosphorus by Fe-Mn oxide/mulberry branch biochar composite adsorbent

In this study, the Fe-Mn oxide/mulberry stem biochar composite adsorbent (FM-MBC) was prepared and fully characterized by SEM-EDS, XRD, BET, and XPS. The solution pH (3.0, 4.5, and 6.0), initial concentration of phosphorus (10, 20, and 30 mg L-1), adsorbent bed height (2, 3, and 4 cm), and solution flow rate (1, 2, and 3 mL min-1) were investigated to analyze the breakthrough curves. The results showed that the breakthrough time was shortened as the initial phosphorus concentration, the flow rate increased and the bed height decreased. Higher initial phosphorus concentrations, flow rates, and lower bed heights, led to a faster breakthrough of phosphate ions in the FM-MBC adsorbent. Additionally, it was observed that increasing the pH value was not conducive to the adsorption of phosphorus by the FM-MBC adsorbent. Dynamic adsorption data were fitted to four models (Yoon-Nelson, Thomas, Adams-Bohart, and Bed Depth Service Time), and the R2 values of the Thomas and Yoon-Nelson models exhibited minimal variation, suggesting that the dynamic adsorption process of FM-MBC was rather intricate. The saturated fixed-bed column (including FM-MBC) was regenerated with NaOH or HCl, and it was found that a 0.1 mol L-1 NaOH solution had the best regeneration effect. XRD analysis showed that the reaction product between the FM-MBC composite and phosphate anions was Fe3(PO4)2·H2O. Moreover, the experimental results that FM-MBC can successfully be used to remove phosphorus from actual wastewater.

Enhanced removing of phosphate ions from agricultural drainage wastewater by using microwave-assisted synthesized attapulgite (Fullers earth) @carboxymethylcellulose nanocomposite

Contamination of various water resources with phosphate pollutant owing to the excessive use of phosphate fertilizers was labeled by dangerous consequences. Most of the water remediation methods are not efficient for phosphate recovery and always generate secondary wastes. Therefore, the current study is aimed to prepare a novel ecofriendly and sustainable APT500@CMC nanocomposite via simple covalent binding of thermally treated attapulgite clay at 500 °C (APT500) with carboxymethyl cellulose (CMC) using microwave irradiation process. The assembled nanocomposite was confirmed by diverse techniques. The optimum conditions for efficient 10, 25 and 50 mg/L PO43- removal were detected at pH 3, time 30 min, temperature 25 °C and mass 200 mg. The kinetic and isotherms were fitted both to a combination of pseudo 1st - 2nd orders and Langmuir model, while thermodynamic parameters verified PO43- removal via spontaneous and exothermic reaction behavior. The mode of interaction and binding of PO43- ions onto the surface of APT500@CMC were suggested via ion-pair interaction process. Excellent PO43- recovery (98.8 %) from real agricultural drainage wastewater was established. The explored APT500@CMC afforded good stability for five regeneration cycles. Therefore, the collected results confirm the validity of APT500@CMC for excellent removal of PO43- from real agricultural drainage wastewater.

Sargassum macroalgae from Quintana Roo as raw material for the preparation of high-performance phosphate adsorbent from aqueous solutions

Currently, the large volumes of Sargassum biomass (Sgs) arriving on Caribbean coasts are a problem that must be solved quickly. One alternative is to obtain value-added products from Sgs. In this work, Sgs is demonstrated to be a high-performance Ca - bioadsorbent for phosphate removal by a heat pretreatment at 800 °C that produces biochar. According to XRD analysis, calcined Sgs (CSgs) have a composition of 43.68%, 40.51%, and 8.69% of Ca(OH)2, CaCO3, and CaO, making CSgs a promising material for phosphate removal and recovery. Results demonstrated that CSgs have a high capacity to adsorb P over a wide range of concentrations (25-1000 mg P/L). After P removal, at low P concentration, the adsorbent material is rich in apatite (Ca5(PO4)3OH), and at high P concentration, brushite (CaHPO4•2H2O) was the main P compound. The CSg reached a Qmax of 224.58 mg P/g, which is higher than other high-performance adsorbents reported in the literature. The phosphate adsorption mechanism was dominated by chemisorption, followed by precipitation according to the pseudo-second-order kinetic model. The solubility of P (74.5 wt%) in formic acid solution and the water-soluble P (24.8 wt%) for CSgs after P adsorption indicated that the final product presents the potential to be used as fertilizer for acid soils. This biomass's processability and high phosphate adsorption performance for P removal make CSgs a potential material for wastewater treatment, and subsequent use of these residues as fertilizer offers a circular economy solution to this problem.

Seasonal variations in the levels of glyphosate in soil, water and crops from three farm settlements in Oyo state, Nigeria

This study investigated the concentration of glyphosate in water (groundwater and surface), soil (top and sub) on cassava and maize farms within 3 farm settlements (Akufo, Ilora and Otiri Ipapo) from Ido, Oyo and Iseyin Local Government Areas of Oyo state, Nigeria. Samples of Top and sub soil were taken from the farms while water was collected from wells (groundwater) and streams (surface water) around each farm settlement using standard methods. Crops (cassava and Maize) samples were collected from each of the selected farm after harvest. The samples were collected over a six-month period to reflect seasonal variation. The glyphosate levels were determined using HPLC-FLD after liquid-liquid extraction technique for water and soxhlet extraction for soil crops The pH, electrical conductivity (EC), total dissolved solids (TDS) values for groundwater were within the WHO limits while values recorded for surface water were above the WHO limits. The phosphate and nitrate values were high in surface water compared to groundwater. High concentration of the exchangeable cations were recorded at the top soil for all the farms with values ranging from 4.0 ± 0.1 to 8.2 ± 0.0 for Ca2+, 2.9 ± 0.0 to 5.1 ± 0.1 for Mg2+, 0.3 ± 0.2 to 0.55 ± 0.0 for Na+, and 0.32 ± 0.0 to 8.2 ± 0.0 for K+. the residual concentration of glyphosate taken from wells and taps (groundwater) were within the maximum concentration of glyphosate in drinking water (0.7 mgL-1). Glyphosate concentrations observed were higher in soil samples from all farm settlements during wet season compared to dry, higher concentrations were also observed in surface water during wet season (August) compared to dry, with Akufo farm settlement having the highest concentrations of 29.40 ± 0.83 mgL-1. The glyphosate residues were also higher in cassava (0.3 ± 0.0 mgKg-1) compared to maize (0.07 ± 0.08 mgKg-1) across each farm settlement. Generally, the higher concentrations observed during wet season in both soil and water samples were as a result of active farm activities during wet season and run off respectively. If herbicide usage is not properly monitored within these settlements, it can pose a threat to aquatic animals and humans around the settlements, thus a sustainable and conservative farming is advised.

Nanoparticles, an Emerging Control Method for Harmful Algal Blooms: Current Technologies, Challenges, and Perspectives

Harmful algal blooms (HABs) are a global concern because they harm aquatic ecosystems and pose a risk to human health. Various physical, chemical, and biological approaches have been explored to control HABs. However, these methods have limitations in terms of cost, environmental impact, and effectiveness, particularly for large water bodies. Recently, the use of nanoparticles has emerged as a promising strategy for controlling HABs. Briefly, nanoparticles can act as anti-algae agents via several mechanisms, including photocatalysis, flocculation, oxidation, adsorption, and nutrient recovery. Compared with traditional methods, nanoparticle-based approaches offer advantages in terms of environmental friendliness, effectiveness, and specificity. However, the challenges and risks associated with nanoparticles, such as their toxicity and ecological impact, must be considered. In this review, we summarize recent research progress concerning the use of nanoparticles to control HABs, compare the advantages and disadvantages of different types of nanoparticles, discuss the factors influencing their effectiveness and environmental impact, and suggest future directions for research and development in this field. Additionally, we explore the causes of algal blooms, their harmful effects, and various treatment methods, including restricting eutrophication, biological control, and disrupting living conditions. The potential of photocatalysis for generating reactive oxygen species and nutrient control methods using nanomaterials are also discussed in detail. Moreover, the application of flocculants/coagulants for algal removal is highlighted, along with the challenges and potential solutions associated with their use. This comprehensive overview aims to contribute to the development of efficient and sustainable strategies for controlling HAB control.

Effect of dewatering conditioners on phosphorus removal efficiency of sludge biochar

Based on the best dehydration effect, this study compared the adsorption phosphorus effect of sludge biochar after sludge conditioning with FeCl3, KMnO4, and cationic polyacrylamide (CPAM). This provided insights into the effects of chemical conditioning during the sludge dewatering stage on the overall phosphate adsorption of the dewatered sludge biochar. The phosphorus adsorption mechanism of the dewatering sludge biochar was analysed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy. Under the optimal pyrolysis temperature (300°C), the phosphate adsorption capacity of FeCl3-conditioned sludge biochar (SB-FeCl3) was increased 77 times of the unconditioned sludge biochar. In different solution environments (e.g. pH and coexisting anions), Phosphate adsorption of SB-FeCl3 was srtrongest when the pH of 9 and contained CO32-. Through the analysis of surface elements and functional groups, it was explained that the phosphorus removal effect of SB-FeCl3 comes from abundant active sites containing iron. Phosphorus release occurred in sludge biochar (SB) during the study. SB-FeCl3 solved SB the release of phosphorus, and improved the adsorption capacity of phosphorus.

Value-added application of cattle manure bottom ash for phosphorus recovery from water and replenishment in soil

This study addresses ways to circulate the flow of phosphorus (P) from water to soil to improve water quality and provide a sustainable supply of P into soil. Here, bottom ash (BA_CCM), the byproduct of the combustion of cattle manure, which is performed for obtaining energy, was used to remove P in wastewater. Next, the P-captured BA_CCM was used as P fertilizer for rice growth. BA_CCM was primarily composed of Ca (49.4%), C (24.0%), and P (9.9%), and the crystalline phases of Ca were calcium carbonate (CaCO₃) and hydroxyapatite (Ca₅(PO₄)₃OH). The mechanism of P removal by BA_CCM involves the formation of hydroxyapatite by reacting Ca²⁺ with PO₄^3-. A reaction time of 3 h was required to achieve P adsorption to BA_CCM, and the maximum P adsorption capacity of BA_CCM was 45.46 mg/g. The increase in solution pH reduced P adsorption. However, at pH > 5, the P adsorption amount was maintained regardless of the pH increase. The presence of 10 mM SO₄^2- and CO₃^2- reduced P adsorption by 28.4% and 21.5%, respectively, and the impact of the presence of Cl^- and NO₃^- was less than 10%. The feasibility of BA_CCM was tested using real wastewater, and 3.33 g/L of BA_CCM dose achieved a P removal ratio of 99.8% and a residual concentration of <0.02 mg/L. The toxicity unit of BA_CCM determined for Daphnia magna (D. magna) was 5.1; however, the BA_CCM after P adsorption (P-BA_CCM) did not show any toxicity to D. magna. BA_CCM after P adsorption was used as an alternative to commercial P fertilizer. Rice fertilized with a medium level of P-BA_CCM showed better agronomic values for most agronomic traits, except root length, than that seen with the commercial P fertilizer. This study suggests that BA_CCM can be used as a value-added product to address environmental issues.

Zirconium Component Modified Porous Nanowood for Efficient Removal of Phosphate from Aqueous Solutions

Rapid urban industrialization and agricultural production have led to the discharge of excessive phosphate into aquatic systems, resulting in a rise in water pollution. Therefore, there is an urgent need to explore efficient phosphate removal technologies. Herein, a novel phosphate capture nanocomposite (PEI-PW@Zr) with mild preparation conditions, environmental friendliness, recyclability, and high efficiency has been developed by modifying aminated nanowood with a zirconium (Zr) component. The Zr component imparts the ability to capture phosphate to the PEI-PW@Zr, while the porous structure provides a mass transfer channel, resulting in excellent adsorption efficiency. Additionally, the nanocomposite maintains more than 80% phosphate adsorption efficiency even after ten adsorption-desorption cycles, indicating its recyclability and potential for repeated use. This compressible nanocomposite provides novel insights into the design of efficient phosphate removal cleaners and offers potential approaches for the functionalization of biomass-based composites.

A novel calcium peroxide/attapulgite-Fe(II) process for high concentration phosphate removal and recovery: Efficiency and mechanism

Phosphorus (P) has been overused in livestock farming, which inevitably results in high-concentration P-containing wastewater. Managing total phosphorus discharge is important to prevent eutrophication in aquatic environments, thus it is critical to develop new technologies for the removal and recovery of high-concentration phosphate. In this study, a novel calcium peroxide/attapulgite (CP/ATP) composite was developed and coupled with Fe(II) for high-concentration phosphate removal and recovery. The results demonstrated that the optimal dosage of the CP/ATP-Fe(II) process was CP/ATP = 0.25 g/L and Fe(II) = 2 mM. The pH effect on phosphate removal was minimal, while phosphate removal efficiency rose by 16.7% with the temperature increased from 10 °C to 25 °C. The co-existing ions exhibited little effect on phosphate removal, and the CP/ATP-Fe(II) process showed effective phosphate removal from the real piggery wastewater. The P content of the precipitates after phosphate removal by this process was as high as 25.82%, indicating its good potential for P recycling. A significant synergistic effect existed in CP/ATP and Fe(II) for phosphate removal, and the SEM-EDS, XRD, Raman and XPS characterization exhibited that the phosphate removal mainly relied on the in-situ-formed Fe(III) and the participation of calcium (Ca) species. Co-precipitation was the predominant mechanism for phosphate removal, and the proportions of Fe(III)-P, Ca-P and Ca-Fe(III)-P in the precipitates were 51.5%, 31.2% and 17.3%, respectively. This study provides a highly efficient process for phosphate removal and recovery from wastewater, and insights into interactions among phosphorus, iron and calcium.

Insight into n-CaO2/SBC/Fe(II) Fenton-like system for glyphosate degradation: pH change, iron conversion, and mechanism

Glyphosate has significant adverse effects on creature and ecological balance. Therefore, the efficient treatment of glyphosate wastewater is of great significance. In this study, nano calcium peroxide (n-CaO₂) was loaded onto activated sludge biochar (SBC), and then Fe(II) was added to construct a Fenton-like system (n-CaO₂/SBC/Fe(II)). SBC played the role of both a dispersant and catalyst, which greatly improved the removal capability of glyphosate. The removal efficiency of glyphosate in the n-CaO₂/SBC/Fe(II) system was as high as 99.6%. The persistent free radicals (PFRs) on SBC can promote the conversion of Fe(III) to Fe(II) in the reaction system, and Fe(II) can be maintained at about 15 mg L^-1 until the reaction reached equilibrium. Due to the synergistic effect of Fe(II) hydrolysis and SBC catalysis, n-CaO₂/SBC/Fe(II) system can effectively remove glyphosate in a wide initial pH range (4.0-10.0), and the pH of the reaction system can be remained in a suitable environment (4.0-6.0) for Fenton-like reaction. Advanced oxidation and chemical precipitation were the main mechanisms for the removal of glyphosate. Most of glyphosate could be oxidized into H₂PO^-₄ anions by breaking the bonds of C-P and C-N, and the H₂PO^-₄ can be further adsorbed and bounded on the surface of the composites. This system overcomes the shortcomings of pH rising and Fe(III) precipitation in the CaO₂-based oxidation systems, and realizes the efficient and complete degradation for glyphosate.

Phosphorus recovery and reuse in water bodies with simple ball-milled Ca-loaded biochar

The demand to control eutrophication in water bodies and the risk of phosphorus scarcity have prompted the search for treatment technologies for phosphorus recovery. In this study, ball-milled Ca-loaded biochar (BMCa@BC) composites were prepared with CaO and corn stover biochar as raw materials by a new ball-milling method to recover phosphorus from water bodies. Experimental results demonstrated that BMCa@BC could efficiently adsorb phosphorus in water bodies with an excellent sorption capacity of 329 mg P/g. Hydrogen bonding, electrostatic attraction, complexation, and surface precipitation were involved in adsorption process. In addition, phosphorus recovered by BMCa@BC had high bioavailability (86.7 % of TP) and low loss (3.3 % of TP) and was a potential slow-release fertilizer. P-laden BMCa@BC significantly enhanced seed germination and growth in planting experiments, proving that it could be used as a substitute for P-based fertilizer. After five cycles of regeneration, BMCa@BC still showed good adsorption recovery and the P-enriched desorption solution could be recovered as Ca-P products with the fertilizer value. Overall, BMCa@BC has good cost-effectiveness and practical applicability in phosphorus recovery. This provides a new way to recover and reuse phosphorus effectively.

Effective Removal of Glyphosate from Aqueous Systems Using Synthesized PEG-Coated Calcium Peroxide Nanoparticles: Kinetics Study, H2O2 Release Performance and Degradation Pathways

Glyphosate (N-phosphonomethyl glycine) is a non-selective, broad-spectrum organophosphate herbicide. Its omnipresent application with large quantity has made glyphosate as a problematic contaminant in water. Therefore, an effective technology is urgently required to remove glyphosate and its metabolites from water. In this study, calcium peroxide nanoparticles (nCPs) were functioned as an oxidant to produce sufficient hydroxyl free radicals (·OH) with the presence of Fe²⁺ as a catalyst using a Fenton-based system. The nCPs with small particle size (40.88 nm) and high surface area (28.09 m²/g) were successfully synthesized via a co-precipitation method. The synthesized nCPs were characterized using transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), Brunauer-Emmett-Teller analysis (BET), dynamic light scattering (DLS), and field emission scanning electron microscopy (FESEM) techniques. Under the given conditions (pH = 3.0, initial nCPs dosage = 0.2 g, Ca²⁺/Fe²⁺ molar ratio = 6, the initial glyphosate concentration = 50 mg/L, RT), 99.60% total phosphorus (TP) removal and 75.10% chemical oxygen demand (COD) removal were achieved within 75 min. The degradation process fitted with the Behnajady-Modirshahla-Ghanbery (BMG) kinetics model. The H₂O₂ release performance and proposed degradation pathways were also reported. The results demonstrated that calcium peroxide nanoparticles are an efficient oxidant for glyphosate removal from aqueous systems.

nZVI-Based Nanomaterials Used for Phosphate Removal from Aquatic Systems

In the last decade, the application of nanoscale zero-valent iron (nZVI) has garnered great attention as an adsorbent due to its low cost, non-toxicity, high porosity, and BET-specific surface area. In particular, the immobilization of nZVI particles onto inorganic and organic substrates (nanocomposites) decreased its agglomeration, allowing them to be effective and achieve greater adsorption of pollutants than pristine nanoparticles (NPs). Although nZVI began to be used around 2004 to remove pollutants, there are no comprehensive review studies about phosphate removal from aquatic systems to date. For this reason, this study will show different types of nZVI, pristine nZVI, and its nanocomposites, that exist on the market, how factors such as pH solution, oxygen, temperature, doses of adsorbent, initial phosphate concentration, and interferents affect phosphate adsorption capacity, and mechanisms involved in phosphate removal. We determined that nanocomposites did not always have higher phosphate adsorption than pristine nZVI particles. Moreover, phosphate can be removed by nZVI-based nanoadsorbents through electrostatic attraction, ion exchange, chemisorption, reduction, complexation, hydrogen bonding, and precipitation mechanisms. Using the partition coefficient (PC) values, we found that sepiolite-nZVI is the most effective nanoadsorbent that exists to remove phosphate from aqueous systems. We suggest future studies need to quantify the PC values for nZVI-based nanoadsorbents as well as ought to investigate their phosphate removal efficiency under natural environmental conditions.

Efficient Removal of Phosphate from Wastewater by a Novel Phyto-Graphene Composite Derived from Palm Byproducts

The increased demand for clean water especially in overpopulated countries is of great concern; thus, the development of eco-friendly and cost-effective techniques and materials that can remediate polluted water for possible reuse in agricultural purposes can offer a life-saving solution to improve human welfare, especially in view of climate change impacts. In the current study, the agricultural byproducts of palm trees have been used for the first time as a carbon source to produce graphene functionalized with ferrocene in a composite form to enhance its water treatment potential. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, X-ray diffraction (XRD), ultraviolet-visible, Fourier transform infrared spectroscopy, zeta potential, thermogravimetric analysis, and Raman techniques have been used to characterize the produced materials. SEM investigations confirmed the formation of multiple sheets of the graphene composite. Data collected from the zeta potential revealed that graphene was supported with a negative surface charge that maintains its stability while XRD elucidated that graphene characteristic peaks were evident at 2θ = 22.4 and 22.08° using palm leaves and fibers, respectively. Batch adsorption experiments were conducted to find out the most suitable conditions to remove PO₄ ^3- from wastewater by applying different parameters, including pH, adsorbent dose, initial concentration, and time. Their effect on the adsorption process was also investigated. Results demonstrated that the best adsorption capacity was 58.93 mg/g (removal percentage: 78.57%) using graphene derived from palm fibers at 15 mg L^-1 initial concentration, pH = 3, dose = 10 mg, and 60 min contact time. Both linear and non-linear forms of kinetic and isotherm models were investigated. The adsorption process obeyed the pseudo-second-order kinetic model and was well fitted to the Langmuir isotherm.

A review of adsorption techniques for removal of phosphates from wastewater

Phosphate is considered the main cause of eutrophication and has received considerable attention recently. Several methods have been used for removal of phosphates in water and these include biological treatment, membrane filtration processes, chemical precipitation, and adsorption. Adsorption technology is highly effective in the removal of phosphate from wastewater even at low phosphate concentrations. Nanomaterials/nanoparticles, carbon-based materials (activated carbon and biochar), and their composites have been widely employed for the adsorptive removal and recovery of phosphate from wastewater due to their exceptional properties such as high surface area and high phosphate adsorption properties. This article is a review of the recently reported literature in the field of nanotechnology and activated carbon for the adsorption of phosphate from wastewater. Highlights of the adsorption mechanisms, adsorption behaviour, experimental parameters, effects of co-existing ions, and adsorbent modifications are also discussed.

Response mechanism of microorganisms to the inhibition of endogenous pollution release by calcium peroxide

To further explore the response mechanism of microorganisms to the synchronous control of nitrogen and phosphorus release from sediments by CaO₂, the spatiotemporal changes in the physical, chemical and biological indicators of the overlying water, interstitial water and sediments in each reactor were measured in the experiment. The experiment results showed that CaO₂ could increase the ammonia monooxygenase activity, nitrite oxidase activity and Nitrospira abundance in the sediment near its dosing position, and enhanced the activities of nitrate reductase and nitrite reductase at a certain distance from the dosing position, thereby promoting nitrogen removal in sediments through the alternating process of nitrification and denitrification. At the same time, the increase of alkaline phosphatase activity and Saccharimonadales abundance in the test groups accelerated the hydrolysis of organic phosphorus, and the P immobilization in sediments was realized through the subsequent precipitation reaction of Ca²⁺ and PO₄^3- under alkaline conditions. In addition, the enhanced activities of dehydrogenase and catalase ensured that CaO₂ would not cause great killing effect on microorganisms when improving the hypoxic conditions and inhibiting endogenous release. As a result, the dissolved product of CaO₂ such as Ca(OH)₂ and H₂O₂ reduced the nutrients concentration and killed the algae, which kept the algae density and chlorophyll a concentration at a low level throughout the test groups. Therefore, this study systematically clarified the microbial mechanism of CaO₂ synchronously controlling the release of nitrogen and phosphorus from sediments, which provided a new idea for the remediation of endogenous pollution in the water system.

Preparation of Iron Salt-Modified Sludge Biochar and Its Uptake Behavior for Phosphate

Residual sludge is a significant waste resource, and the preparation of biochar achieves sludge disposal. Biochar has a high uptake capacity for phosphate. To prepare a sludge biochar adsorbent for phosphate, sludge was chemically and anaerobically treated in the presence of iron salts and pyrolyzed. We investigated the effects of the pyrolysis temperature and iron salt on the phosphate uptake capacity, finding that the pretreatment of the sludge with iron salts removed intrinsic phosphate, thus improving the uptake ability. The optimal adsorbent, denoted SB-B-Fe, was prepared by pyrolysis at 700 °C and subsequently modified with a 20 g/L iron-containing solution, yielding a phosphate uptake capacity of 0.5 mg/g. Further, the performance of SB-B-Fe remains high at pH 5–9 and is less affected by interfering anions. The sorption kinetics are consistent with the pseudo-second-order kinetic model, suggesting uptake by chemisorption, and the Langmuir model has a saturation capacity of 0.85 mg/g for uptake and prefers monolayer molecular uptake. The characterization showed that the adsorbent surface provided many uptake sites for phosphate and a high specific surface area. We hope that these findings will encourage the development of other value-added waste-based materials for environmental remediation.

Simultaneous and efficient removal of fluoride and phosphate in phosphogypsum leachate by acid-modified sulfoaluminate cement

The high concentration of fluoride and phosphate in phosphogypsum leachate is harmful to the environment and ecosystem. Thus, there is a need to develop feasible materials or technologies to remove both fluoride and phosphate in acidic phosphogypsum leachate. In this study, sulfoaluminate cement (SC) was used to simultaneously remove fluoride and phosphate in wastewater based on its moderate alkalinity and rich content of metal elements (Ca, Al and Fe, etc). The acidized sulfoaluminate cement (ASC) composite was prepared through modifying SC with hydrochloric acid, which can increase the specific surface areas of the raw SC, as well as the activity of the metal elements in SC. Compared with other coagulants, ASC showed excellent removal performance for fluoride and phosphate, such as higher removal efficiency, better effluent quality, and accelerated settling rate. The fluoride and phosphate removal performances of ASC herein were investigated at different dosages, pH values, coexisting substances, and initial concentrations. As a result, ASC exhibited wide pH adaptability and satisfactory selectivity for fluoride and phosphate. The possible removal mechanisms of fluoride and phosphate by ASC included chemisorption, ion exchange, and precipitation. The main end products associated with fluoride were fluorite (CaF₂), aluminum fluoride (AlF₃), and iron trifluoride (FeF₃). The main final products amid phosphate removal, on the other hand, were brushite (CaHPO₄·2H₂O), aluminophosphate ((H₃O)·AlP₂O₆(OH)₂), silicocarnotite (Ca₂SiO₄·Ca₃(PO₄)₂) and iron phosphate (Fe(H₂PO₄)₃). More importantly, ASC can effectively treat the phosphogypsum leachate at a wide range of concentrations, and the concentrations of phosphate and fluoride in the effluents were lower than 0.5 mg P L^-1 and 4 mg L^-1, respectively. To sum up, ASC is a competitive candidate to treat wastewater with high fluoride and phosphate content, such as phosphogypsum leachate.

Degradation of 4-nonylphenol in marine sediments using calcium peroxide activated by water hyacinth (Eichhornia crassipes)-derived biochar

The contamination of marine sediments by 4-nonylphenol (4-NP) has become a global environmental problem, therefore there are necessaries searching appropriate and sustainable remediation methods for in-situ applications. Herein, water hyacinth [(WH) (Eichhornia crassipes)]-derived metal-free biochar (WHBC) prepared at 300-900 °C was used to promote the calcium peroxide (CP)-mediated remediation of 4-NP-contaminaed sediments. At [CP] = 4.37 × 10^-4 M, [WHBC] = 1.5 g L^-1, and pH = 6.0, the degradation of 4-NP was 77% in 12 h following the pseudo-first order rate law with rate constant (k_obs) of 4.2 × 10^-2 h^-1. The efficient 4-NP degradation performance and reaction mechanisms of the WHBC/CP system was ascribed to the synergy between the reactive species (HO• and ¹O₂) at the WHBC surface on which there were abundant electron-rich carbonyl groups and defects/vacancies in the catalyst structure provides active sites, and the ability of the graphitized carbon framework to act as a medium for electron shuttling. According to microbial community analysis based on amplicon sequence variants, bacteria of the genus Solirubrobacter (Actinobacteria phylum) were dominant in WHBC/CP-treated sediments and were responsible for the biodegradation of 4-NP. The results showed great promise and novelty of the hydroxyl radical-driven carbon advanced oxidation processes (HR-CAOPs) that relies on the value-added utilization of water hyacinth for contaminated sediment remediation in achieving circular bioeconomy.

Phosphorus removal and recovery: state of the science and challenges

Phosphorus is one of the main nutrients required for all life. Phosphorus as phosphate form plays an important role in different cellular processes. Entrance of phosphorus in the environment leads to serious ecological problems including water quality problems and soil pollution. Furthermore, it may cause eutrophication as well as harmful algae blooms (HABs) in aquatic environments. Several physical, chemical, and biological methods have been presented for phosphorus removal and recovery. In this review, there is an overview of phosphorus role in nature provided, available removal processes are discussed, and each of them is explained in detail. Chemical precipitation, ion exchange, membrane separation, and adsorption can be listed as the most used methods. Identifying advantages of these technologies will allow the performance of phosphorus removal systems to be updated, optimized, evaluate the treatment cost and benefits, and support select directions for further action. Two main applications of biochar and nanoscale materials are recommended.

Converting wastes to resource: Utilization of dewatered municipal sludge for calcium-based biochar adsorbent preparation and land application as a fertilizer

Pyrolysis combined with land application for dewatered municipal sludge disposal revealed advantages in heavy metals solidification and resource utilization compared with other disposal technologies. In this study, utilizing dewatered municipal sludge for calcium-containing porous adsorbent preparation via pyrolysis was proposed and verified. After pyrolyzing at 900 ° C (Ca-900), the dewatered sludge obtained maximum adsorption capacity (83.95 mg P⋅ g^-1) and the adsorption process conformed to the pseudo-second-order model and double layer model. Characteristic analysis showed the predominant adsorption mechanism was precipitation. Continuous column bed experiment indicated 2 g adsorbent could remove 4.27 mg phosphorus from tail wastewater with the initial phosphorus concentration of 1.03 mg ⋅ L^-1. No heavy metals leaching was observed from Ca-900 adsorbent with pH value exceeding 1.0, and merely 1% addition of Ca-900 adsorbent (after actual water phosphorus adsorption) with soil could extremely promote the early growth of seedlings. Economic estimates demonstrated that this cost-effective modification could generate the most add-on value production. Based on these results, the strategy of 'one treatment but two uses' was proposed in this study, converting the wastes to resource and providing a native strategy for sludge disposal and resource recovery.

Control of arsenic release from paddy soils using alginate encapsulated calcium peroxide

The mobilization of As in paddy soils is affected by iron redox cycles. In this regard, calcium peroxide (CaO₂) can be used as an alternative to maintaining oxidizing conditions by liberating oxygen under flooding environments. Nevertheless, the problem of increase in pH by CaO₂ dissolution remains unresolved. In this study, the encapsulation of CaO₂ using alginate is proposed. Encapsulated CaO₂ (CaO₂-b) using 1% sodium alginate was applied to As-contaminated soil to evaluate the ability of pH control and As mobility during flooding conditions. The pH increased rapidly from 6.8 to 9.0 in unencapsulated CaO₂ (CaO₂-p) within 1 day, while CaO₂-b increased slowly to 8.6 over 91 days. CaO₂ created an oxidizing condition in the soil by providing oxygen, thus effectively prevented the reductive dissolution of iron. The mobility of As decreased by 50% (CaO₂-p) and 83% (CaO₂-b) compared with that of the control soil. Furthermore, the As in pore water was three times lower than CaO₂-p because CaO₂-b released 1.8 times more Ca²⁺ to form Ca-As complexes than CaO₂-p. Consequently, the encapsulated CaO₂ reduced the negative effects of CaO₂ treatment on increasing pH of the soil and furnished a better environmental condition for inhibiting As mobility.

Metal-free carbocatalysts derived from macroalga biomass (Ulva lactuca) for the activation of peroxymonosulfate toward the remediation of polycyclic aromatic hydrocarbons laden marine sediments and its impacts on microbial community

Potential toxic chemicals, specifically, polycyclic aromatic hydrocarbons (PAHs), are major sediment contaminants. Herein, green seaweed (Ulva lactuca) was used as a feedstock and pyrolyzed at temperature in the range between 300 and 900 °C. The metal-free carbocatalyst (GSBC) for peroxymonosulfate (PMS) activation to degrade PAHs contaminated sediments was studied. The effects of GSBC‒PMS treatment on microbial community abundance was studied as well. The pyrolysis temperature of GSBC preparation affected the PMS activation performance. Results show that GSBC700 exhibited remarkable catalytic characteristics in PAHs degradation by effective activation of PMS. The results also demonstrated that the sulfate radical-carbon-driven advanced oxidation processes (SR-CAOP) reaction achieved 87% and apparent rate constant (k_obs) of 6.3 × 10^-2 h^-1 of total PAHs degradation in 24 h at 3.3 g/L of GSBC, PMS dose of 1 × 10^-4 M, and pH 3.0. The degradation of 2-, 3-, 4-, 5-, and 6-ring PAHs was 84, 83, 83, 80, and 89%, respectively. The synergetic effect established between GSBC and PMS enhanced the formation of ROSs, namely, SO₄^-, HO, and ¹O₂, which were major species contributing to PAHs degradation. The synergistic effect of π‒π stacking structure and graphitization of GSBC formed electron shuttle, which contributed to PAHs degradation performance. Microbial community structure analyses in the GSBC‒PMS treated sediments showed that the relative abundance of Lactobacillus_rhamnosus species, most of which belonged to the Lactobacillus genus and Firmicutes phylum, which aided in continuing PAHs biodegradation post GSBC‒PMS treatment. Therefore, GSBC can be a promising carbocatalyst produced via biomass-to-biochar conversion as biowaste-to-energy source used in the SR-CAOP-mediated process for sediment remediation.

Persistent free radicals in biochar enhance superoxide-mediated Fe(III)/Fe(II) cycling and the efficacy of CaO2 Fenton-like treatment

Superoxide radicals (O₂^•-) produced by the reaction of Fe(III) with H₂O₂ can regenerate Fe(II) in Fenton-like reactions, and conditions that facilitate this function enhance Fenton treatment. Here, we developed an efficient Fenton-like system by using calcium peroxide/biochar (CaO₂/BC) composites as oxidants and tartaric acid-chelated Fe(III) as catalysts, and tested it for enhanced O₂^•--based Fe(II) regeneration and faster sulfamethoxazole (SMX) degradation. SMX degradation rates and peroxide utilization efficiencies were significantly higher with CaO₂/BC than those with CaO₂ or H₂O₂ lacking BC. The CaO₂/BC system showed superior activity to reduce Fe(III), while kinetic analyses using chloroform as a O₂^•- probe inferred that the O₂^•- generation rate by CaO₂/BC was one-half of that by CaO₂. Apparently, O₂^•- is utilized more efficiently in this system to regenerate Fe(II) and enhance SMX degradation. Additionally, a positive correlation between SMX degradation rate constants and EPR signal intensities of biochar-derived persistent free radicals (PFRs) in CaO₂/BC was obtained. We postulate that PFRs enhanced Fe(III) reduction by shuttling electrons donated by O₂^•-. This represents a new strategy to augment the ability of superoxide to accelerate Fe(III)/Fe(II) cycling for increased hydroxyl radical production and organic pollutant removal in Fenton-like reactions.

Facile synthesis of Fe-modified lignin-based biochar for ultra-fast adsorption of methylene blue: Selective adsorption and mechanism studies

A novel Fe-modified lignin-based biochar (Fe-LB) was fabricated via a facile one-step carbonization method for methylene blue (MB) removal from wastewater. Fe-LB exhibited a high specific surface area (885.97 m²/g) and micropore volume (0.3203 m³/g), and demonstrated high affinity for MB with the maximum adsorption capacity of 2.7-fold by Fe-LB than LB. It was found that quick adsorption could be achieved in 15 min with the MB removal efficiency of 100% and adsorption capacity reached 200 mg/g. Selective adsorption studies indicated that Fe-LB preferentially adsorbed MB in high salt and multiple dye systems (binary, ternary, and quaternary) over a wide pH range from 2 to 12. The removal efficiency of CR was greatly improved due to the synergistic effect between MB and CR in the binary system. This work demonstrated that Fe-LB can effectively remove dye contaminants and possessed great potential in the treatment of MB polluted dye wastewater.

Unraveling the Ca-P species produced over the time during phosphorus removal from aqueous solution using biocomposite of eggshell-palm mesocarp fiber

Phosphorus (P) adsorption from aqueous solutions is usually evaluated by monitoring the P concentration and employed kinetic models. In this work, three adsorbents obtained from eggshell (ES) and eggshell mixed with palm mesocarp fiber (ESF-1:1 and ESF-1:10) at different Ca(OH)₂/CaCO₃ compositions were evaluated, and the Ca-P species formed monitored as a function of time deconvoluting Fourier Transform Infrared (FTIR) spectra. At 0.25 h the ESF-1:10 (Ca(OH)₂: 26.2 wt%) exhibited better adsorption performance of 35 mgg^-1 while ESF-1:1 and ES (Ca(OH)₂: 2.8 and 3.0 wt%) showed 26 and 4 mgg^-1, respectively. Characteristic PO₄^3- bands in apatite were corroborated by XRD and FTIR. It was found that the role of Ca(OH)₂ in the adsorption ends before 0.25 h, and thereafter CaCO₃ becomes the phase responsible for the removal of orthophosphate H₂PO₄^-/HPO₄^2-/PO₄^3- ions. The results indicate a direct ligand exchange of CO₃^2- for PO₄^3- that takes place while increasing the apatite crystallinity. On the other hand, the P adsorption process is also dependent on P concentration. At low P concentrations, characteristic bands of PO₄^3- in apatite were observed in FTIR, while at high concentrations, characteristic bands for adsorbed HPO₄^2- were obtained. The obtained results give a relevant role to CaCO₃ in P adsorption. Kinetic analysis for Ca-based biocomposites showed that the Avrami order kinetic model fits better for the adsorbents. For P adsorption isotherm process the Langmuir's isotherms showed a good fit, with a maximum adsorption capacity of 90.8, 134.0, and 67.9 mgg^-1 for ES, ESF-1:1, and ESF-1:10, respectively.

Phosphate adsorption characteristics of La(OH)3-modified, canna-derived biochar

La(OH)₃-modified canna biochar (CBC-La) was prepared by a coprecipitation method (dipping method), and its phosphate adsorption characteristics were investigated. The results show that the pseudo-second-order kinetics and the Langmuir model can be used to describe the adsorption process with a high level of accuracy. Adsorption equilibrium could be reached at 8 h, at which point the maximum adsorption capacity was shown to be 37.37 mg/g. CBC-La has excellent phosphate adsorption capacity in the middle to low concentrations (≤50 mg/L), and its removal rate can exceed 99 %. CBC-La also has wide pH adaptability (3-9) and a strongly selective adsorption performance. Notably, it can still maintain a removal rate of over 99.8 % in the presence of certain anions (NO₃^-, HCO₃^-, and CO₃^2-), and the presence of NH₄⁺ has a synergistic effect on the adsorption process. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements demonstrate that the main mechanisms of CBC-La phosphate adsorption are electrostatic adsorption, ion exchange, ligand exchange and inner sphere complexation.

Valorization of potato peels and eggshells wastes: Ca-biocomposite to remove and recover phosphorus from domestic wastewater

Potato peel (PP) waste are generated in huge quantities, causing environmental pollution and health problems. Therefore, obtaining value-added products from PP is a current research challenge. In this work, novel Ca-biocomposites for phosphorus (P) removal were prepared by pyrolysis (500-800 °C) using eggshell (ES) and PP (ES/PP = 1:2 ratio by weight). ESPP-700 (pyrolyzed at 700 °C), reached a Q_max of 174.8 mg P/g, while the application of Ca-biocomposites in domestic wastewater showed 85.96% of P removal. According to the pseudo-second-order kinetic model, P adsorption was dominated by chemisorption, follows by apatite precipitation. The P solubility (62.5 wt.%) in formic acid (2.0 wt.%) and the water-soluble P (3.2 wt.%) for ESPP-700 after P adsorption, indicated that the final product would work as fertilizer for acidic soils. This is an important step in the management of agricultural wastes to implement the 3R slogan "Reduce, Reuse, Recycle" towards a circular economy.

Removal of phosphorus from wastewater by Diutina rugosa BL3: Efficiency and pathway

A novel phosphorus removal yeast BL3 was isolated from an alternating anaerobic/aerobic biofilter and identified as Diutina rugosa by 26S rDNA gene sequence analysis. Yeast BL3 could effectively remove phosphorus from synthetic wastewater containing 2-20 mg/L phosphorus under optimal environmental conditions. The highest phosphorus removal efficiency was above 70% under the conditions of DO 6.86 mg/L, C/P ratios of 60, N/P ratios of 3.3, pH 6.0-9.0, and at 25.0-35.0 °C. The phosphorus distribution in the aqueous solution and different components of yeast BL3 analysis indicated that around 55%-70% and 20%-40% of removed phosphorus were transferred into extracellular polymeric substances (EPS) and yeast cells, respectively. The plausible phosphorus transfer pathway was proposed based on the phosphorus distribution and species analysis, suggesting the important role of EPS as a phosphorus reservoir. These results indicate that yeast BL3 can efficiently remove phosphorus under aerobic conditions without alternating anaerobic/aerobic cycling, and thus has significant potential for practical application in wastewater phosphorus removal.

Efficient reclaiming phosphate from aqueous solution using waste limestone modified sludge biochar: Mechanism and application as soil amendments

A novel limestone-modified biochar derived from sewage sludge was prepared to reclaim phosphorus (P) from aqueous solution, and the potential application of P-laden biochar as soil amendments was also investigated. The limestone-modified biochar demonstrated excellent performance on phosphate recovery from aqueous solution in a wide range of pH (2.0-11.0), with maximum adsorption capacity of the biochar (Limestone/sludge mass ratio of 3:1) up to 231.28 mg P/g, which was 10.7 times that of the original sludge biochar. The adsorption was well described by the pseudo second-order model and Langmuir isotherm model. According to the adsorption thermodynamic parameters, the phosphate adsorption was spontaneous (ΔG⁰ < 0) and endothermic (ΔH⁰ > 0) so that increasing the temperature was beneficial to adsorption. Characterization analysis by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscope-energy dispersive spectrometer (SEM-EDS) proved that electrostatic attraction, surface complexation and brushite (CaHPO₄^.2H₂O) precipitation were the dominant mechanism. The P-laden biochar exhibited an excellent ability to be reused as a new slow-release P fertilizer for soil. Pot experiment results showed that the treatment of P-laden LB 3:1 (P content of 22.8%) addition (1 wt%) significantly promoted Indian Lettuce germination (increasing by 14.4%), plant height (increasing by 18.6%), and dry biomass (53.0%) compared with the control, though it underperformed compared to commercial fertilizer.

Biochar affects the fate of phosphorus in soil and water: A critical review

Biochar is a promising novel material for managing phosphorus (P), a nutrient often limiting for primary production but can also be a pollutant, in the environment. Reducing P input to the environment and finding cost-effective approaches to remediate P contamination are major challenges in P management. There is currently no review that systematically summarizes biochar effects on soil P availability and its P removal potential from water systems. In this paper, we comprehensively reviewed biochar effects on soil P availability and P removal from water systems and discussed the mechanisms involved. Biochar affects soil P cycling by altering P chemical forms, changing soil P sorption and desorption capacities, and influencing microbial population size, enzyme activities, mycorrhizal associations and microbial production of metal-chelating organic acids. The porous structure, high specific surface area, and metal oxide and surface functional groups make biochars effective materials for removing P from eutrophic water via ligand exchange, cation bridge, and P precipitation. Because soil and biochar properties are widely variable, the effect of biochar on the fate of P in soil and water systems is inconsistent among different studies. Knowledge gaps in the economic practicability of large-scale biochar application, the longevity of biochar benefits, and the potential ecological risks of biochar application should be addressed in future research.

Recent advances and challenges on removal and recycling of phosphate from wastewater using biomass-derived adsorbents

As the severe damage of phosphate enrichment in the water ecosystem and the supply shortage of phosphate rock, developing an efficient method for the removal and recycling of phosphate from wastewater is of great significance. To achieve this goal, adsorption technology has been widely investigated, and various adsorbents were developed. Among them, the biomass-derived adsorbents including biomass-derived carbon-based materials, biomass-based anion exchangers and metal-biomass composites have attracted increasing attention over the past years due to the low cost, abundant renewable raw materials and environmental friendliness. However, different adsorbents usually exhibit variable adsorption performances for phosphate, which highly depends on their design strategies, preparation methods and potential adsorption mechanisms. Thus, this review comprehensively summarizes the recent researches on the removal and recycling of phosphate from wastewater using the biomass-derived adsorbents. Especially, the design strategies, preparation methods, adsorption performances and mechanisms of these reported biomass-derived adsorbents are discussed in detail. Moreover, as the significant strategies to recover and recycling phosphate, the elution and direct use of phosphate-loaded adsorbents as fertilizers are also presented. Although the excellent adsorption performance has been obtained, some challenges are still existing, which should be given more attention in the following researches to facilitate the development and industrial application of biomass-derived adsorbents.

Degradation of diclofenac sodium using Fenton-like technology based on nano-calcium peroxide

A nano-calcium peroxide (nCaO₂) powder with a purity of 89.1% was prepared using an improved traditional method. Then, the as-prepared nCaO₂ was used as the source of hydrogen peroxide (H₂O₂) for the Fenton-like degradation of diclofenac sodium (DCF). The results showed that nCaO₂ performed better for DCF removal when compared to nCaO₂ prepared by a conventional method and commercial calcium peroxide (CaO₂). Further experimental results indicated that 97.5% of DCF could be removed in 180 min at a nCaO₂/Fe²⁺-EDTA/DCF molar ratio of 16/8-8/1, which was more efficient than in the H₂O₂/EDTA-Fe²⁺/DCF and nCaO₂/Fe²⁺/DCF systems. The best removal rate of DCF was at pH 6.0, unlike previous claims that stated that the lower the pH in the buffer system, the better the degradation of DCF. In addition, the influence of water quality parameters, such as Cl^-, NO₃^-, SO₄^2-, HCO₃^-, and humic acid (HA), on DCF removal were evaluated. A free radical masking experiment revealed the existence of hydroxyl radical (OH), superoxide radical (O₂^-) and singlet oxygen (¹O₂), and indicated that the degradation of DCF was mainly due to oxidation caused by OH. Electron paramagnetic resonance (EPR) studies for different systems and different active oxygen species were carried out, and it was further confirmed that OH radicals have high intensity in the Fenton-like system based on nCaO₂. EPR results also showed that the addition of EDTA can promote the production of OH. According to the identification of the dominant reactive species and GC-MS, the possible theoretical DCF degradation pathways were proposed.

Formation and mechanisms of nano-metal oxide-biochar composites for pollutants removal: A review

Biochar, a carbon-rich material, has been widely used to adsorb a range of pollutants because of its low cost, large specific surface area (SSA), and high ion exchange capacity. The adsorption capacity of biochar, however, is limited by its small porosity and low content of surface functional groups. Nano-metal oxides have a large SSA and high surface energy but tend to aggregate and passivate because of their fine-grained nature. In combining the positive qualities of both biochar and nano-metal oxides, nano-metal oxide-biochar composites (NMOBCs) have emerged as a group of effective and novel adsorbents. NMOBCs improve the dispersity and stability of nano-metal oxides, rich in adsorption sites and surface functional groups, maximize the adsorption capacity of biochar and nano-metal oxides respectively. Since the adsorption capacity and mechanisms of NMOBCs vary greatly amongst different preparations and application conditions, there is a need for a review of NMOBCs. Herein we firstly summarize the recent methods of preparing NMOBCs, the factors influencing their efficacy in the removal of several pollutants, mechanisms underlying the adsorption of different pollutants, and their potential applications for pollution control. Recommendations and suggestions for future studies on NMOBCs are also proposed.

Computational study of phosphate adsorption on Mg/Ca modified biochar structure in aqueous solution

Phosphate removal in water using biochar is widely investigated. Density functional theory was used to study the adsorption of phosphate (H₂PO₄^-) on biochar in water after metal modification. Two types of metals, Mg and Ca, were used to modify the biochar structure, and the edge and metal adsorptions of H₂PO₄^- were investigated on the modified biochar structure. Results were analyzed from the aspects of structural stability, adsorption energy, change in dipole moment, density of electronic states, and atoms in molecules analysis. The overall effect of metal-modified biochar materials on phosphate adsorption was stronger than that of unmodified biochar materials in terms of molecular level. The stability of the metal-modified structure by adding metal was low, and adsorption was prone to occur in this situation. The Ca-modified biochar showed better phosphate adsorption than the Mg-modified structure. Metal adsorption performed better than edge adsorption, proving that the modified metal in the biochar structure played a leading role in H₂PO₄^- adsorption. Metal adsorption was mainly caused by electrostatic attraction, and edge adsorption was mainly caused by covalent bonding.