Phosphate Removal Efficiency Research Articles

Efficient removal and recovery of phosphate from wastewater by nano-CaO2/BFS sorbent and its potential as a slow-release phosphate fertilizer

Facing the dual pressure of eutrophication control and global phosphorus scarcity, the efficient removal and recovery of phosphate from wastewater has attracted growing attention in recent years. Herein, an efficient nanocomposite (nCaO2-BFS) was successfully synthesized through a facile coprecipitation method by loading nano-calcium peroxide (nCaO2) onto blast furnace slags (BFS) and used for phosphate removal and recovery from wastewater. Based on the preliminary screening of as-prepared nCaO2-BFS sorbents regarding phosphate removal efficiency, the nCaO2-BFS nanocomposite prepared with a CaCl2-to-BFS mass ratio of 0.6:1, NH3·H2O amount of 20 mL, and H2O2 amount of 12 mL was selected for further characterization and phosphate elimination. Results showed that the developed nCaO2-BFS sorbent exhibits a superior adsorption capacity of 67.48 mg·g-1, a broadly applicable pH range from 4 to 10, and strong selectivity for phosphate in the presence of competing anions including Cl-, NO3-, SO42-, HCO3-, and CO32-. Mechanistically, surface precipitation and inner-sphere complexation via ligand exchange were identified as the primary sorption mechanism for nCaO2-BFS in capturing phosphate. The plant growth test confirmed that the phosphate-laden nCaO2-BFS sorbent could be used as a slow-release fertilizer to promote the growth of Brassica rapa L. Therefore, applying nCaO2-BFS appears to be a promising method for remediating excessive phosphate and recovering the non-renewable phosphorus resource.

Endowing turbostratically porous carbon with rich edge nitrogen active sites for efficient capacitive removal of phosphate

The mitigation of phosphate in water is a pivotal concern for the prevention of eutrophication and enhancement of water quality. Capacitance deionization (CDI) technique possesses the merits of high removal efficacy, facile operation, and environmental friendliness, rendering it a promising strategy for phosphate elimination. Herein, the nitrogen-rich laminar porous carbon composites (NTPCs) prepared by direct pyrolysis of supermolecular precursor were utilized as phosphate capture electrodes. The resulting NTPC800 features a high nitrogen content turbostratically amorphous carbon framework, which facilitates efficient ion diffusion pathways and electron transfer. The abundant presence of edge nitrogen (pyridine and pyrrole nitrogen) optimizes the electronic structure of the carbon system and provides more active sites, thus leading to the boosted electrochemical activity and dephosphorization efficiency. Consequently, NTPC800 demonstrates a rapid phosphate removal capacity, achieving 73.51 mg g−1 within a mere 10 min at 1.2 V condition, which is nearly 6 times more efficient than that of the commercial activated carbon electrode. Moreover, it exhibited consistent phosphate removal efficiency across various pH ranges, coexisting ion interferences, and cyclic stability assessments. This study provides theoretical support for the utilization of edge nitrogen decorated carbonaceous electrodes to enhance charge transfer and provide additional active sites for efficient capacitive dephosphorization.

Lanthanum-modified tobermorite synthesized from fly ash for efficient phosphate removal.

Phosphate removal from water by lanthanum-modified tobermorite synthesized from fly ash (LTFA) with different lanthanum concentrations was studied. LTFA samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and Brunauer‒Emmett‒Teller specific surface area analysis. The results showed that the LTFA samples were mainly composed of mesoporous tobermorite-11Å, and LTFA1 with a lanthanum concentration of 0.15M had a high specific surface area (83.82 m2/g) and pore volume (0.6778 cm3/g). The phosphate adsorption capacities of LTFA samples were highest at pH 3 and gradually decreased with increasing pH. The phosphate adsorption kinetics data on LTFA samples were most accurately described by the Elovich model. The adsorption isotherms were in the strongest agreement with the Temkin model, and LTFA1 showed the highest phosphate adsorption capacity (282.51mg P/g), which was higher than that of most other lanthanum-modified adsorbents. LTFA1 presented highly selective adsorption of phosphate with other coexisting ions (HCO3-, Cl-, SO42-, and NO3-). In addition, phosphate was adsorbed onto LTFA samples by forming inner-sphere phosphate complexes and amorphous lanthanum phosphate. This study provides technical support for development of efficient fly ash-based phosphate adsorbents.

Efficient phosphate removal by Mg-La binary layered double hydroxides: synthesis optimization, adsorption performance, and inner mechanism.

Layered double hydroxides (LDH) hold great promise as phosphate adsorbents; however, the conventional binary LDH exhibits low adsorption rate and adsorption capacity. In this study, Mg and La were chosen as binary metals in the synthesis of Mg-La LDH to enhance phosphate efficient adsorption. Different molar ratios of Mg to La (2:1, 3:1, and 4:1) were investigated to further enhance P adsorption. The best performing Mg-La LDH, with Mg to La ratio is 4:1 (LDH-4), presented a larger adsorption capacity and faster adsorption rate than other Mg-La LDH. The maximum adsorption capacity (87.23 mg/g) and the rapid adsorption rate in the initial 25 min of LDH-4 (70 mg/(g·h)) were at least 1.6 times and 1.8 times higher than the others. The kinetics, isotherms, the effect of initial pH and co-existing anions, and the adsorption-desorption cycle experiment were studied. The batch experiment results proved that the chemisorption progress occurred on the single-layered LDH surface and the optimized LDH exhibited strong anti-interference capability. Furthermore, the structural characteristics and adsorption mechanism were further investigated by SEM, BET, FTIR, XRD, and XPS. The characterization results showed that the different metal ratios could lead to changes in the metal hydroxide layer and the main ions inside. At lower Mg/La ratios, distortion occurred in the hydroxide layer, resulting in lower crystallinity and lower performance. The characterization results also proved that the main mechanisms of phosphate adsorption are electrostatic adsorption, ion exchange, and inner-sphere complexation. The results emphasized that the Mg-La LDH was efficient in phosphate removal and could be successfully used for this purpose.

Analysis of coconut shell adsorption capability as greywater waste adsorbent

As coconut plantations increase in Indonesia, coconut shell waste has the potential to damage the environment if it is not processed properly. Various studies state that coconut shell waste can be used as a greywater adsorbent. Greywater is a domestic waste that is much less polluted than domestic wastewater because it does not contain urine, feces, and toilet paper, and only contains about 30% of the total organic load. Therefore, it is important to determine the right adsorbent for appropriate processing. So this research will test the adsorption capacity of coconut shell waste as a greywater adsorbent using iodine absorption analysis. In the analysis of iodine absorption capacity, coconut shell adsorbents have high adsorption capabilities in absorbing adsorbate (iodine molecules) with high molecular concentrations. Based on iodine absorption analysis data, it is known that the coconut shell waste adsorbent has a maximum adsorption capacity of 2.86 x 10-3 mg g-1 by following the Langmuir isotherm model. The coconut shell waste adsorbent used as a medium in the adsorption column was able to reduce total dissolved solids by 3.7 %, total suspended solids by 23.3 %, and phosphate removal efficiency by 6.3 % in greywater waste samples. This proves that coconut shell waste can act as an adsorbent in managing greywater waste.

Ca–Mg modified attapulgite for phosphate removal and its potential as phosphate-based fertilizer

The urgent concerns of controlling water body eutrophication and the alleviating phosphorus shortage have led to an urgent need for action. The removal of phosphate from polluted waters and its reuse are essential for the prevention of eutrophication and for the sustainable utilization of phosphate resources. In this study, modified attapulgite with different Ca:Mg molar ratios was synthesized to facilitate the recovery of phosphate, with subsequent use of soil fertilizer. Ca–Mg modified attapulgite with the optimal ratio (ACM-5:3) exhibited an exceptional adsorption quality, achieving a maximum adsorption capacity of 63.2 mg/g. The pseudo-second-order model and Langmuir model could well describe the adsorption kinetics and isotherms, respectively. The adsorption mechanism analyses suggested that the interaction between ACM-5:3 and phosphate depended mainly on ion exchange and electrostatic attraction. Moreover, phosphate-laden-ACM-5:3 demonstrated a significant potential as a phosphorus-releasing fertilizer. It could promote corn growth by ensuring a continuous supply of phosphorus and minimizing phosphorus runoff losses. The above results suggested that ACM-5:3 was a potential adsorbent for efficient phosphate removal and recovery.

Enhanced removal of phosphate from aqueous solutions by oxygen vacancy-rich MgO microspheres: Performance and mechanism

The efficient removal of phosphate from water environments was extremely significant to control eutrophication of water bodies and prevent further deterioration of water quality. In this study, oxygen vacancy-rich magnesium oxide (OV–MgO) microspheres were synthesized by a simple solvothermal method coupling high-temperature calcination. The effects of adsorbent dosage, contact time, initial pH and coexisting components on phosphate adsorption performance were examined. The physicochemical properties of OV-MgO microspheres and the phosphate removal mechanisms were analyzed by various characterization techniques. The maximum adsorption capacity predicted by the Sips isotherm model was 379.7 mg P/g for OV-MgO microspheres. The phosphate adsorption in this study had a fast adsorption kinetics and a high selectivity. OV-MgO microspheres had a good acid resistance for phosphate adsorption, but their adsorption capacity decreased under alkaline conditions. The electrostatic attraction, ligand exchange, surface precipitation, inner-sphere surface complexation and oxygen vacancy capture were mainly responsible for efficient removal of phosphate from aqueous solutions. This study probably promoted the development of oxygen vacancy-rich metal (hydr)oxides with potential application prospects.

Sub-pilot scale sequential microalgal consortium-based cultivation for treatment of municipal wastewater and biomass production

Municipal wastewater (MWW) was treated by a sequential pilot microalgal cultivation process. The cultivation was performed inside a specifically designed low-cost photobioreactor (PBR) system. A microalgal consortium 2:1 was developed using Tetraselmis indica (TS) and Picochlorum sp. (PC) in the first stage and PC:TS (2:1) in the second stage and the nutrient removal efficiency and biomass production and biomolecules production was evaluated and also compared with monoculture in a two-stage sequential cultivation system. This study also investigated the effect of seasonal variations on microalgae growth and MWW treatment. The results showed that mixed microalgal consortium (TS:PC) had higher nutrient removal efficiency, with chemical oxygen demand (COD), total phosphate (TP), and total nitrate (TN) removal efficiencies of 78.50, 84.49, and 84.20%, respectively, and produced a biomass of 2.50 g/L with lipid content of 37.36% in the first stage of cultivation under indoor conditions. In the second stage of indoor cultivation, the PC:TS consortium demonstrated maximum COD, TP, and TN removal efficiencies of 92.49, 94.24, and 94.16%, respectively. It also produced a biomass of 2.65 g/L with a lipid content of 40.67%. Among all the seasonal variations, mass flow analysis indicated that the combination of mixed consortium-based two-stage sequential process during the winter season favored maximum nutrient removal efficiency of TN i.e. 88.54% (84.12 mg/L) and TP i.e., 90.18% (43.29 mg/L), respectively. It also enhanced total biomass production of 49.10 g in 20-L medium, which includes lipid yield ∼15.68 g compared to monoculture i.e., 82.06% (78.70 mg/L) and 82.87% (40.26 mg/L) removal of TN and TP, respectively, and produced biomass 43.60 g with 11.90 g of lipids.

Influence of toilet flushing water when using an on-site faecal sludge treatment combining electrocoagulation-flotation and anaerobic digestion

Addressing the need for sustainable sanitation in public transport and tourism, this study evaluates electrocoagulation-flotation (ECF) combined with anaerobic digestion (AD) for treating synthetic human faecal sludge (FS). Especially the effects of influent aeration and the use of either rainwater or tap water for flushing on the efficiency of pollutant removal and methane production were investigated. In detail, flushing with rainwater combined with influent aeration resulted in the highest removal efficiency of total COD (tCOD), non-soluble COD (nsCOD), total nitrogen (TN), and total phosphate (TP) of 55 %, 27 %, 22 %, and 75 %, respectively, during ECF treatment, compared to 48 %, 15 %, 14 %, and 63 %, respectively, when tap water was used. As such, post-treatment is mainly necessary for the removal of TN. Combining flushing with rainwater and influent aeration also resulted in the highest faradeic efficiency (107 %) and the most insoluble iron coagulant formation. In contrast, the application of influent aeration during ECF of FS produced using rainwater flushing led to a decrease in methane production from 354 mL/g VS (when no aeration is applied) to 281 mL/g VS during subsequent AD. In conclusion, this study demonstrates that ECF can be applied as a good pre-treatment for sanitation water due to the high nsCOD and TP removal, by which ECF could replace, e.g., a septic tank. Furthermore, the potential of combining ECF with AD is demonstrated in view of energy recovery.

Eco-friendly nanoparticles: mechanisms and capacities for efficient removal of heavy metals and phosphate from water using definitive screening design approach.

Can nano-zero-valent iron, synthesized using oak leaf extract, be the key solution for water preservation, efficiently removing heavy metal ions and phosphate anions simultaneously? This research unveils how this technology not only promises high efficiency in the remediation of water resources, but also sets new standards for environmentally friendly processes. The high antioxidant capacity and high phenol content indicate suggest the possibility of oak-nZVI synthesis using oak leaf extract as a stable material with minimal agglomeration. The simultaneous removal of Cd and phosphates, as well as and Ni and phosphates was optimized by a statistically designed experiment with a definitive screening design approach. By defining the key factors with the most significant impact, a more efficient and faster method is achieved, improving the economic sustainability of the research by minimizing the number of experiments while maximizing precision. In terms of significance, four input parameters affecting process productivity were monitored: initial metal concentration (1-9mgL-1), initial ion concentration (1-9mgL-1), pH value (2-10), and oak-nZVI dosage (2-16mL). The process optimization resulted in the highest simultaneous removal efficiency of 98.99 and 87.30% for cadmium and phosphate ions, respectively. The highest efficiency for the simultaneous removal of nickel and phosphate ions was 93.44 and 96.75%, respectively. The optimization process fits within the confidence intervals, which confirms the assumption that the selected regression model well describes the process. In the context of e of the challenges and problems of environmental protection, this work has shown considerable potential and successful application for the simultaneous removal of Cd(II) and Ni(II) in the presence of phosphates from water.

Loofah sponge crosslinked polyethyleneimine loaded with biochar biofilm reactor for ecological remediation of oligotrophic water: Mechanism, performance, and functional characterization

The removal of complex pollutants from oligotrophic water is an important challenge for researchers. In this study, the HCl-modified loofah sponge crosslinked polyethyleneimine loaded with biochar (LS/PEI@biochar) biofilm reactor was adapted to achieve efficient removal of complex pollutants in oligotrophic water. On the 35 d, the average removal efficiency of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), calcium (Ca2+), and phosphate (PO43--P) in water was 51, 95, 81, and 77 %, respectively. Additionally, it effectively used a low molecular weight carbon source. Scanning electron microscopy (SEM) results showed that the LS/PEI@biochar biocarrier had superior biofilm suspension performance. Meanwhile, analysis of the biocrystals confirmed Ca2+ and PO43- removal through the generation of CaCO3 (calcite and vaterite) and Ca5(PO4)3OH. This study demonstrated that the system has great efficiency and application prospect in treating oligotrophic water on the laboratory scale, and will be further validated for practical application on large-scale oligotrophic water.

A Novel Method of Synthesizing Polymeric Aluminum Ferric Sulfate Flocculant and Preparing Red Mud-Based Ceramsite.

A synthetic flocculant of aluminum (Al) and iron (Fe) extracted from red mud (RM) has been widely used in sewage treatment, while the remaining RM residue has been ignored. This study aimed to synthesize polymeric aluminum ferric sulfate (PAFS) flocculant from RM by acid leaching and then use the acidified RM residue to produce an acid RM-based ceramsite (ARMC) by mixing bentonite, hydroxypropyl methylcellulose, and starch. Our results showed that sintering, reaction temperature, H2SO4 concentration, reaction time, and liquid-to-solid ratio had an obvious effect on the leaching of Al and Fe in RM, which was a necessary prerequisite for the efficient PAFS flocculants. At a PAFS dosage of 60 mg/L, turbidity and phosphate removal rates were 95.21 ± 0.64% and 89.17 ± 0.52%, respectively. When the pH value was 8.0, the turbidity and phosphate removal efficiency were 99.22 ± 0.66% and 95.98 ± 1.63%, respectively. Considering the adsorption capacity and mechanical properties, the best conditions for ARMC production included using 60% ARM and ceramsite calcination at 600 °C, with the BET surface area 56.16 m2/g and a pore volume of 0.167 cm3/g. Thermogravimetric analysis indicated that 400 °C was a reasonable preheating temperature to enhance the ARMC mechanical strength, as this temperature allows the removal of surface-adsorbed and constituent water. Under a scanning electron microscope, the ARMC appeared rough before adsorption, while relatively uniform pores occupied it after adsorption. Our conclusion will help to improve the zero-waste strategy of RM and speed up the industrial production of RM in flocculants as well as utilizing ARMC as a new type of adsorbent for phosphorus adsorption in sewage treatment.

Characteristic and mechanism of efficient phosphate removal by Portland cement/slag powder/coal ash-hydrate (PC/SP/CA-H)

The excessive presence of phosphate in water leads to eutrophication, prompting us to develop a novel material named PC/SP/CA-H (Portland cement/slag powder/coal ash-hydrate). The experimental data accorded with the pseudo-second-order kinetics and Langmuir model, suggesting that chemical interactions predominated in the adsorption process. Within 4 hours, PC/SP/CA-H rapidly removed phosphate at a rate of 65%, which exceeded 90% after 12 hours with a material dosage of 30 g/L and a phosphate concentration of 30 mg/L. The maximum phosphate adsorption capacity of PC/SP/CA-H was 8.84 mg/g. The material exhibited effective phosphate removal capabilities across a wide pH range of 3.0–11.0. It demonstrated remarkable selectivity to phosphate in the presence of competitive anions, such as CO32-, HCO3-, NO3-, SO42-, and Cl-. Characterization analyses including SEM, BET, XRD, XRF, FTIR, and XPS were conducted to investigate the performance of PC/SP/CA-H and mechanisms of phosphate removal. The findings indicated that phosphate replaced hydroxyl groups on the material to form inner-sphere complexes through ligand exchange. Besides, phosphate was adsorbed onto the positively charged material via electrostatic attraction with protonated hydroxyl groups (-OH2+). It also reacted with metal cations (Ca2+) released by the material to form insoluble crystalline substances (Ca-P) through surface precipitation. This material holds promising prospects for efficiently removing phosphate from water or wastewater, while simultaneously enhancing the resource utilization of coal ash and slag powder.

Treatment of wet coffee processing wastewater using a pulsed-electrocoagulation process: optimization using response surface technique

In this study, the removal efficiency of chemical oxygen demand (COD), color, turbidity, phosphate, and nitrate from wet coffee processing wastewater by pulsed-electrocoagulation process (PECP) was examined with various factors such as pH: 3–11, reaction time: 15–75 min, current: 0.150–0.750 Amp, and electrolyte concentration: 0.25–1.25 g/L. Several operational parameters for the treatment of wet coffee processing wastewater utilizing the PECP have been optimized through the application of the surface response design technique, which is based on the central composite design. A quadratic model helped estimate the percentage removal of COD, color, turbidity, phosphate, and nitrate with power consumption under various situations. It also evaluated the significance and their interaction with independent variables using analysis of variance (ANOVA). Through the use of statistical and mathematical techniques, optimum conditions were determined in order to remove the maximum pollutant and nutrient while using the minimum of power. The results showed that the removal of COD—98.50%, color—99.50%, turbidity—99.00%, phosphate—99%, and nitrate—98.83%, with a power consumption of 0.971 kWh m−3 were achieved at pH-7, NaCl dose of 0.75 g/L, electrolysis duration of 45 min, and current of 0.45 Amp. Therefore, under the different operating conditions, the PECP demonstrated to be a successful technique for pollutant removal from wastewater and industrial effluent.

A green synthesis strategy toward calcined calcium-aluminum layered double hydroxide with sludge as aluminum source for efficient removal of phosphate from water

Layered double hydroxides promise efficient phosphorus removal from water, yet their preparation process inevitably leads to the consumption of metal minerals and incurs high material costs. The drinking water treatment aluminum sludge with high aluminum content is a suitable source for obtaining metal aluminum. Recognizing the environmental and economic challenges in traditional layered double hydroxides production, this research proposes a novel approach utilizing high-aluminum drinking water treatment aluminum sludge as an alternative aluminum source. Herein, calcium-aluminum layered double oxides with aluminum sludge as aluminum source (Ca/(Al-DWTAS)-LDOs) were prepared by co-precipitation and calcination method. The study meticulously examines the influence of variables such as dosage, initial pH, and the presence of coexisting ions on phosphorus removal efficiency: at the optimal dosage (0.5 g/L), the adsorption efficiencies of Ca/(Al-DWTAS)-LDOs for phosphate in the range of 2.0 < pH < 11.0 and in the environment of common anionic disturbances were maintained at more than 90%. After six adsorption-desorption tests, the phosphate removal efficiency of Ca/(Al-DWTAS)-LDOs only decreased from 98.85% to 74.38%. According to the Sips isotherm model, the maximal adsorption capacity of Ca/(Al-DWTAS)-LDOs at ambient temperature (25 °C) was determined to be 110.14 mg/g. Adsorption mechanism of Ca/(Al-DWTAS)-LDOs were explored through characterization, kinetic and thermodynamic studies, mainly involving electrostatic reactions, ion exchange reaction, surface complexation reaction, and surface precipitation. When 0.5 g/L Ca/(Al-DWTAS)-LDOs was added to the actual swine wastewater with phosphate content of 37.25 mg/L, the phosphate removal efficiency reached 86.19%. This study not only provides an alternative process method for the acquisition of layered double hydroxides, but also has wide applications for environmental protection.

Eichhornia crassipes Leaves as a Waste-derived Bio-Sorbent to Remove Organics and Nutrients from Rice Mill Wastewater

The increased rate of population growth resulted in the increased number of rice mill industries to fulfill the demand for rice. The rice mill wastewater contains a high load of organics and nutrients. Therefore, the direct discharge of wastewater into the environment may degrade the quality of the environment as well as causes adverse effects on human health. Among various methods to treat waste effluent, bio-sorption is a cheap and environmentally sound approach. Eichhornia crassipes is a noxious weed that spreads rapidly. Most of the tanks in Vavuniya are polluted by E. crassipes and it needs a sustainable solution. This study uses the leaves of E. crassipes to produce waste-derived bio-sorbent to treat rice mill wastewater. The wastewater was collected from one of the rice mills in the Vavuniya town area. The adsorption isotherm and adsorption kinetics experiments were conducted to find out the removal efficiencies of COD, nitrate, and phosphate from wastewater. The effect of the dosage of bio-sorbent (1-6 g/L) and the contact time (30-180 min) with the wastewater was studied to determine the optimum dosage and optimum contact time. The bio-sorbent showed maximum removal efficiencies of COD (54.5%), nitrates (58.1%), and phosphates (29.5%) at the optimum dosage of 4 g/L at 120 min. Based on the t-test, E. crassipes leaves significantly reduce COD, nitrate, and phosphate (p-value&lt;0.05). However, COD and nitrate showed higher removal rates than phosphate. Further, long-term column studies should be conducted to apply the above technique in wastewater treatment plants in treating the rice mill wastewater in the real world. This study emphasizes that E. crassipes leaves have the potential to remove contaminants from wastewater as well as this would also help to minimize the spread of the weed to safeguard the environment. &#x0D; Keywords: Eichhornia crassipes, Bio-sorption, Vavuniya tank, Water quality

Enhanced nutrient recovery from anaerobically digested poultry wastewater through struvite precipitation by organic acid pre-treatment and seeding in a bubble column electrolytic reactor

Limited mineralization of organic phosphorus to phosphate during the anaerobic digestion process poses a significant challenge in the development of cost-effective nutrient recovery strategies from anaerobically digested poultry wastewater (ADPW). This study investigated the influence of organic acids on phosphorus solubilization from ADPW, followed by its recycling in the form of struvite using a bubble column electrolytic reactor (BCER) without adding chemicals. The impact of seeding on the efficiency of PO43− and NH3-N recovery as well as the size distribution of recovered precipitates from the acid pre-treated ADPW was also evaluated. Pre-treatment of the ADPW with oxalic acid achieved complete solubilization of phosphorus, reaching ∼100% extraction efficiency at pH 2.5. The maximum removal efficiency of phosphate and ammonia-nitrogen from the ADPW were 88.9% and 90.1%, respectively, while the addition of 5 and 10 g/L struvite seed to the BCER increased PO43− removal efficiency by 9.6% and 11.5%, respectively. The value of the kinetic rate constant, k, increased from 0.0176 min−1 (unseeded) to 0.0198 min−1, 0.0307 min−1, and 0.0375 min−1 with the seed loading rate of 2, 5, and 10 g/L, respectively. Concurrently, the average particle size rose from 75.3 μm (unseeded) to 82.1 μm, 125.7 μm, and 148.9 μm, respectively. Results from XRD, FTIR, EDS, and dissolved chemical analysis revealed that the solid product obtained from the recovery process was a multi-nutrient fertilizer consisting of 94.7% struvite with negligible levels of heavy metals.

Efficient Removal of Phosphate from Aqueous Solutions Using Corundum- hollow-spheres Supported Caclined Hydrotalcite Porous Thin Films

Efficient Removal of Phosphate from Aqueous Solutions Using Corundum- hollow-spheres Supported Caclined Hydrotalcite Porous Thin Films

Efficient phosphate removal from water by multi-engineered PVA/SA matrix double network hydrogels: Influencing factors and removal mechanism

Development of environmentally friendly absorbent with superior adsorption performance and environmental adaptability is of great concern. In this study, multi-engineered polyvinyl alcohol (PVA)/sodium alginate (SA) matrix double network hydrogels (named as MGPA) were manufactured by freeze thawing and La(III)-ionic crosslinking and used for phosphate removal from water. Basic physicochemical parameters, swelling feature and other surface characters of as-prepared samples were firstly studied. The desired hydrogel displayed better mechanical properties, low swelling feature, and good separability, etc. Batch adsorption experiments have also shown that it has good adsorption performance at pH 3–12, making it widely operable. The adsorption behavior was further examined through adsorption kinetics and isotherms. The optimized MGPA-3 hydrogel (with 0.1 M La(III) in crosslinking) displayed the maximum experimental sorption capacity of ∼38.75 mg P/g and equilibrium time of 120 min, which was better than most of similar sorbents. It maintained good selectivity with the coexistence of anions and dissolved organic matters as well as in practical water treatment. Besides, superior environmental adaptability in dynamic adsorption studies and adsorption-desorption experiments were confirmed. Overall, electrostatic attraction, ligand/anion exchange, and Lewis acid-base interactions may jointly promote the pH-independent adsorption process for phosphate.

Performance of novel Ca-biocomposites produced from banana peel and eggshell for highly efficient removal and recovery of phosphate from domestic wastewater

Using biowaste-based adsorbents to remove phosphorus (P) from wastewater offers significant benefits concerning eutrophication mitigation and addressing waste management challenges. In this work, Ca-biocomposites were prepared by pyrolysis (700 °C) of a mixture of banana peel (BP) and eggshell (ES). The mass ratio of BP to ES was varied in 2:1, 1:1, and 1:2 ratios. Among the tested mixtures, the BPES-1:2 sample exhibited excellent P removal performance, reaching a maximum P adsorption capacity (Qmax) of 214 ± 5 mg P/g. The adsorption process fitted well with the Avrami order kinetic model (R2 > 0.996) and the Liu isotherms model (R2 > 0.997). The excellent fit of the experimental data to the Avrami model suggests that chemisorption is the dominant interaction mechanism, leading to precipitation through the formation of calcium phosphates. Additionally, the Liu model anticipates that the energetic characteristics of the adsorbent's active sites cannot be identical. This is in agreement with the presence of Ca(OH)2 and CaCO3 in the adsorbent material, where the Ca(OH)2 active sites are preferred by the adsorbate molecules (PO43−) for occupation. Furthermore, thermodynamic analysis revealed that P adsorption is a spontaneous process of exothermic nature (ΔH° < 0). The calculated activation energy for the process (72.81 kJ/mol) suggests the P adsorption mechanism involves strong chemical bonding between the adsorbent and P species. In addition, precipitation of apatite (Ca5(PO4)3OH), a vital component in fertilizer production, was observed during the adsorption process. In tertiary treated wastewater applications, the BPES-1:2 biocomposite demonstrated a P removal efficiency of 90%. The solubility of P in a 2% formic acid solution was 100%, while the water-soluble P content was measured at 5.6%. These findings highlight the product's sustainable and environmentally beneficial nature by demonstrating its potential as a slow-release fertilizer, contributing to the application of the 3R slogan: Reduce, Reuse, Recycle. This value-added product is promising in supplying nutrients to plants over an extended period while minimizing the risk of nutrients leaching into the environment.