Phosphate Adsorption Performance Research Articles

Facile and scalable synthesis of long-life porous MgO-nanofiber functionalized biochar adsorbent from magnesite for phosphate recycling

The recycling of phosphate from wastewater using regenerable and highly efficient MgO-modified biochar for Mg-P fertilizer application is of great interest. However, the practical application of MgO-modified biochar for the removal and recycling of phosphate is hindered by its short-recycled service-life. Herein, a facile yet scalable method is proposed to fabricate porous MgO nanofiber-functionalized biochar (PMgNF-BC) with enhanced phosphate adsorption and regeneration performances from wastewater using waste biomass and magnesite. The as-prepared PMgNF-BC exhibited the maximum phosphate adsorption capacities of 594.53, 661.57, and 725.43 mg/g at 298.15 K, 308.15 K and 318.15 K, respectively. More importantly, PMgNF-BC demonstrated excellent regeneration performance with the removal efficiency of 84.2 % after eight regeneration cycles. Furthermore, the regenerated PMgNF-BC exhibited the well-preserved fiber shape of MgO on BC, enabling splendid regeneration performance. This work validates PMgNF-BC as a sustainable adsorbent for recycling phosphorus from wastewater, addressing the urgent need for synthesizing biochar with high regeneration performance.

Development and validation of an adsorption process for phosphate removal and recovery from municipal wastewater based on hydrotalcite-related materials

In the current international context characterized by the tendency to stricter limits for P concentration in treated wastewater and a strong drive towards phosphate recovery, it is crucial to develop cost-effective technologies to remove and recover phosphate from municipal wastewater (MWW). In this study, an initial screening of the phosphate adsorption performances of 9 sorbents including several hydrotalcites led to the selection of calcined pyroaurite - an innovative material composed of mixed Mg/Fe oxides - as the best-performing one. The assessment of calcined pyroaurite by means of isotherms and continuous-flow adsorption/desorption tests conducted with actual MWW resulted in a high P sorption capacity (12 mgP g−1 at the typical phosphate concentration in MWW), the capacity to treat 730 BVs at the 1 mgP L−1 breakpoint imposed by the current EU legislation, and a 93 % phosphate recovery. Calcined pyroaurite resulted in satisfactory performances also in a test conducted with a saline MWW deriving from a hotspot of seawater intrusion, a rapidly increasing phenomenon as a result of climate change. Five consecutive adsorption/desorption cycles conducted in a 20-cm column at a 5-min empty bed contact time resulted stable in terms of P adsorption/recovery performances, specific surface area and chemical structure of calcined pyroaurite. In the perspective to apply phosphate recovery with calcined pyroaurite at full scale, the process scale-up to a 60-cm packed bed - close to the column heights of industrial applications - resulted in stable performances. Calcium phosphate, widely used to produce phosphate-based fertilizers, can be obtained from the desorbed product by precipitation with Ca(OH)2. These results point to calcined pyroaurite as a very promising material for phosphate removal and recovery from MWW and from other P-rich effluents in a circular economy perspective.

Liquidizing crystal MIL-100(Fe) to coating silica powder for purifying wastewater

Although MIL-100(Fe) was regarded as an ideal material for the environmental remediation, it could not be applied in practical because of the potential eco-environmental risk and cost. In this work, a novelty strategy of liquidizing crystal MIL-100(Fe) was posted for the first time through inhibiting the crystallization process and forming physical MIL-100(Fe) gel. Due to this MIL-100(Fe) sol–gel, MIL-100(Fe) could easy cover on the surface of silica powder (SiO2) through simple soaking operation. MIL-100(Fe) covering on SiO2 (MIL-100(Fe)@SiO2) could be quickly separated from wastewater spontaneously owing to the carrier of SiO2, even in a tank of 2.0 m, which made it possible for purifying wastewater in practical. MIL-100(Fe)@SiO2 could remove phosphate with a removing ratio of closing 100 % at an initial concentration of 10 mg/L, while more than 95 % towards methyl orange (MO). The removing ratio of MO by MIL-100(Fe)@SiO2 did not obviously decrease when the concentration of MO increased to 100 mg/L. And the adsorption performance of phosphate did not affect by pH among 3.0–9.0. The adsorption amount exceeded 50 % of maximum adsorption capacity for phosphate within 30 min, while 90 % for MO. Monodentate mononuclear coordination could explain the adsorption of phosphate by MIL-100(Fe)@SiO2. The N atom in MO might be acted as Lewis acid to coordinate with MIL-100(Fe)@SiO2. After adsorption, the P-saturated and MO-saturated MIL-100(Fe)@SiO2 could be effectively regenerated by the dilute HCl and NaOH solution, respectively. The recovery ratio of adsorption capacity for phosphate and MO were up to 97.7 % and 71.6 %.

Innovative strategy of turning waste into treasure: High-efficiency adsorption of heavy metals pollutants by modified amorphous calcium phosphate prepared with phosphogypsum waste

In the present work, phosphogypsum (PG) waste was used as a calcium source, and integrated with 2-hydroxyphosphonoacetic acid (HPA) doping, modified inorganic-organic amorphous calcium phosphate hybrid composite was prepared, to remove Cd2+ and Co2+in aqueous solution. The study demonstrated that when pH=8, the equilibrium adsorption capacity of hydroxyapatite (HAP) for Cd2+ and Co2+ can reach 275.84 mg/g and 70.63 mg/g, respectively. After modification with HPA, the adsorption capacity of 20HPA-HAP for Cd2+ and Co2+ was higher at 468.92 mg/g and 171.38 mg/g, respectively. Regeneration experiments show that the adsorbent has good recycling performance, and the adsorbent has a good adsorption effect on low-concentration cadmium and cobalt ions in the actual hard gold electroplating wastewater. Meanwhile, the adsorption mechanism of 20HPA-HAP for Cd2+ and Co2+ was vividly visualized through Multiwfn wavefunction program and VMD program. Therefore, the reason why doping HPA greatly improves the adsorption performance of amorphous calcium phosphate on heavy metal ions was revealed from the atomic point of view. The findings suggest a promising approach for the effective utilization of discarded PG and the effective treatment of heavy metal pollution in industrial wastewater, highlighting the dual benefit of waste material repurposing and pollution control, which was an innovative strategy of turning waste into treasure.

Selective phosphate removal by lanthanum carbonate @ anion exchange resin with fixed-bed column: RSM for process optimization and DFT for mechanistic study

Lanthanum carbonate @ anion exchange resin (LC@AER) has shown promise in adsorption processes due to its high maximum adsorption capacity and excellent stability in comparison with other lanthanum-based adsorbents. Nevertheless, there is a lack of significant investigation in evaluating the collective effect of the most influential parameters and determining the molecular complexes between the adsorbent and phosphate. This work aims to comprehensively evaluate and optimize the phosphate adsorption performance in fixed-bed columns and to determine the most favourable molecular configurations. Firstly, a response surface model (RSM) was developed to describe the phosphate adsorption performance in fixed-bed columns under the collective effect of selected independent variables, including influent pH, co-existing sulfate concentration, and empty bed contact time (EBCT). The RSM analysis reveals the significant effects of influent pH and co-existing sulfate concentration on phosphate adsorption. Moreover, the model achieves a correlation coefficient of >0.9, demonstrating its suitability for describing the experimental data. Secondly, various phosphate-lanthanum carbonate configurations were formulated, and the respective adsorption energies were compared using density functional theory (DFT) calculations. Subsequently, bidentate mononuclear complexes are determined as the most favourable configurations. The successful matching of the simulated peak locations with the experimental deconvoluted spectra further confirms the presence of such complexes in the system. Overall, this work provides an improved foundation and underlayer theory for potential future scale-up work on phosphate adsorption over LC@AER.

Efficient phosphate adsorption in aqueous solution using nano-zirconia impregnated spent coffee grounds and preliminary application as a slow-release fertilizer

ABSTRACT In this study, the development of a nano-biocomposite adsorbent based on spent coffee grounds (SCG) and nano-Zirconia (n-ZrO2) was presented to meet the increasing demand for effective and low-cost phosphate adsorbents and contribute to sustainable development goals (SDGs). The adsorption performance of raw SCG and SCG modified with n-ZrO2 (n-ZrO2-mSCG) was tested. The characterization of materials was performed by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), BET surface area analysis, thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), Dispersive X-ray spectroscopy (EDS), and Transmission electron microscopy (TEM). The n-ZrO2-mSCG exhibited superior adsorption capacity compared to SCG. The influences on the adsorption of factors such as initial concentration, pH, stirring time, temperature, and coexisting ions were evaluated. The results showed the maximal adsorption capacity of modified SCG was 15.8 mg/g at pH 2, using a stirring time of 150 mins. Among investigated coexisting anions, sulfate (SO4 2-) and bicarbonate (HCO3 −) affected the phosphate adsorption performance of n-ZrO2-mSCG, when they existed in aqueous solution at predominant levels. The n-ZrO2-mSCG displayed high selectivity toward phosphate and sustained efficacious phosphate adsorption after three successive cycles of adsorption/desorption, proposing a prospective low-cost and reusable adsorbent material for phosphate removal and a potential alternative to conventional fertilizers.

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.

Low-cost eggshell-fly ash adsorbent for phosphate recovery: A potential slow-release phosphate fertilizer

Fly ash (FA) and eggshells (ES) are common solid wastes with significant potential for the recovery of phosphorus from water. This study focuses on synthesizing a low-cost and environmental-friendly phosphate adsorbent called eggshell-fly ash geopolymer composite (EFG) using eggshells instead of chemicals. The CaO obtained from the high-temperature pyrolysis of eggshells provides active sites for phosphate adsorption, and CO2 serves as a pore-forming agent. The phosphate adsorption performance of EFG varied with the eggshell-fly ash ratios and achieved a maximum of 49.92 mg P/g at an eggshell-fly ash ratio of 40 %. The adsorption process was well described by the pseudo-second-order model and the Langmuir model. EFG also exhibited a good regeneration performance through six-cycle experiments and achieved the highest phosphate desorption at pH 4.0. The results of the column experiment showed that EFG can be used as a filter media for phosphorus removal in a real-scale application with low cost. Soil burial test indicated saturated EFG has a good phosphate slow-release performance (maintained for up to 60 days). Overall, EFG has demonstrated to be a promising adsorbent for phosphorus recovery.

MgO-modified biochar by modifying hydroxyl and amino groups for selective phosphate removal: Insight into phosphate selectivity adsorption mechanism through experimental and theoretical

Metal oxides-modified biochars have been widely studied as promising adsorbents for removing phosphate from wastewater discharge. Yet, the low adsorption selectivity towards phosphate severely limits its potential in practical applications. In this study, MgO-modified biochar modified by hydroxyl and amino groups (OH/NH2@MBC) is developed for selective phosphorus recovery from wastewater. As major results, the OH/NH2@MBC exhibits favorable phosphate adsorption performance is superior to that of MBC resin in the presence of co-existing anions (NO3−, Cl−, HCO3− and SO42−) and natural organic matter (humic acid) even actual wastewater, suggesting its superior selectivity towards phosphate. The OH/NH2@MBC shows an excellent phosphate adsorption capacity (43.27 mg/g) and desorption ratio (82.34 %) after five cycles under the condition of anion coexistence (100 mg/L). The experimental and DFT theoretical study reveals that attaching hydroxyl and amino groups onto the MBC surface, which facilitates to inhibiting the side effects of anions (NO3−, Cl−, HCO3−, and SO42−) through Lewis acid-base sites, hydrogen bonds, and metal affinity, and preferentially select adsorption P, contributing greatly to improve phosphate adsorption selectivity. Importantly, the presence of amino and hydroxyl groups can reduce the Fermi level of OH/NH2@MgO(220) and OH/NH2@MgO(200) and improve the adsorption selection for HPO42−. This study provides an effective strategy for enhancing the adsorption selectivity of metal oxides-modified biochars towards phosphate through modifying functional groups.

Recovering Phosphate from Complex Wastewater Using Macroporous Cryogel Composited Calcium Silicate Hydrate Nanoparticles.

Since currently used natural, nonrenewable phosphorus resources are estimated to be depleted in the next 30-200 years, phosphorus recovery from any phosphorus-rich residues has attracted great interest. In this study, phosphorus recovery from complex wastewater samples was investigated using continuous adsorption on cryogel column composited calcium silicate hydrate nanoparticles (CSH columns). The results showed that 99.99% of phosphate was recovered from a synthetic water sample (50 mg L-1) using a 5 cm CSH column with a 5 mL min-1 influent flow rate for 6 h while 82.82% and 97.58% of phosphate were recovered from household laundry wastewater (1.84 mg L-1) and reverse osmosis concentrate (26.46 mg L-1), respectively. The adsorption capacity decreased with an increasing flow rate but increased with increasing initial concentration and column height, and the obtained experimental data were better fitted to the Yoon-Nelson model (R2 = 0.7723-0.9643) than to the Adams-Bohart model (R2 = 0.6320-0.8899). The adsorption performance of phosphate was decreased 3.65 times in the presence of carbonate ions at a similar concentration, whereas no effect was obtained from nitrate and sulfate. The results demonstrate the potential of continuous-flow phosphate adsorption on the CSH column for the recovery of phosphate from complex wastewater samples.

Synthesis of Al-modified hydrochar from corn stover for efficient phosphate removal

The development of a simple and feasible process for preparing adsorbent materials to recover phosphorus resources would have significant environmental and social benefits. In this study, the Al-modified hydrochar was synthesized for phosphate adsorption by hydrothermal carbonization in one pot using corn stover as raw material. The results showed that phosphate adsorption mainly depended on the precipitation reaction between Al element and phosphate, in which the hydrochar carrier played a synergistic role. Al element through the hydrothermal treatment loaded on hydrochar expressed a much higher phosphate adsorption performance than that on pyrochar. When the concentration of AlCl3 solution added in the hydrothermal process was 2 mol·L−1 and the hydrothermal temperature exceeded 180 ℃, Al element could transform from the amorphous state, which was less effective for phosphate adsorption, to Al24O11(OH)44Cl6 crystal with high adsorption performance and could be more stably loaded onto the hydrochar. Although the preparation process was simple, the adsorption performance of hydrochar is good. The phosphate adsorption capacity and removal efficiency by the hydrochar prepared at 260 °C reached to 114.40 mg·g−1 and 76.27%, which could be further increased by adjusting the dosage of adsorbent and pH of water. The pseudo-second-order kinetic model and Langmuir isotherm model could better describe the phosphate adsorption process on Al-loaded hydrochar. Phosphate was rapidly adsorbed on the surface of the hydrochar rich in mesoporous structure and bound to the surface-active sites. This study could transform agricultural waste into a functional hydrochar-based adsorbent and provide a low-cost, simple operation and efficient phosphate removal technology.

Hydrothermal synthesis of lanthanum oxide nanoparticles modified pumice: High lanthanum oxide loading ratio and efficiency phosphate removal

Efficient and less restrictive phosphorus pollution treatment methods are required to treat water eutrophication. Lanthanum oxide nanoparticles modified pumice (LOMP) with a high loading ratio was prepared by a simple hydrothermal synthesis method which adjusted the synthesis conditions. The XRD, SEM, and TEM results show that the lanthanum oxide nanoparticles have successfully modified on the surface of the pumice, forming a disordered hierarchical structure. The adsorption kinetics results showed that phosphate adsorption was more consistent with the pseudo-second-order model. The adsorption isotherm was more consistent with the Sips model, and the theoretical adsorption capacity was 82.77 mg P/L. The results of the effects of the initial pH and the coexisting anions indicate that LOMP has a good phosphate removal efficiency in a wide range of pH and a strong ability to resist the competition of anions. The superior phosphate adsorption performance can be ascribed to the ligand exchange, which also can be promote by hydrogen ions.

Prediction of phosphate adsorption amount, capacity and kinetics via machine learning: A generally physical-based process and proposed strategy of using descriptive text messages to enrich datasets

The use of machine learning to predict phosphate adsorption performance by specific adsorbent holds great promise due to its ability to save time and reveal underlying mechanisms. However, the small size of the dataset, caused by the insufficient detailed information, limits the ability to fully train the model and obtain accurate and generalizable results. To address this issue, we employ a fuzzing strategy that substitutes detailed numeric information with descriptive text messages on the physiochemical properties of adsorbents (such as using “Porous Carbon” to substitute the adsorbent with 100 < SBET < 500 m2⋅g−1 and with C content > 10 wt%). This strategy allows the recovery of the discarded samples that are short in detailed information, which delivers the enrichment of dataset and the accurate prediction of adsorption amount, capacity, and kinetics. The adsorption amount is determined by environmental pressures, while adsorption capacity and kinetics are subject to a synergism of environmental pressures and physicochemical properties of adsorbents. Comprehensive analysis finds that phosphate uptake by adsorbents is generally via physisorption, although chemisorption also plays a role. This study has constructed a framework that requires only the input of common and easily accessible information to quickly predict phosphate adsorption performance by specific adsorbent, which is highly practical, especially in urgent scenarios. Additionally, our strategy provides useful guidelines for recovering discarded samples and enriching the dataset by fuzzing detailed information.

Effect of Modified Biochar Prepared by Co-pyrolysis of MgO on Phosphate Adsorption Performance and Seed Germination.

Biochar is currently used as a phosphate adsorbent in water and subsequently as a soil amendment. In this study, modified biochar was prepared directly by co-pyrolysis of MgO and rice straw, and a preliminary ecotoxicological assessment was performed before the application of modified biochar to soil. The effects of single factors, such as pyrolysis temperature, dosage, pH, and coexisting ions, on phosphate adsorption performance were investigated. In addition, after phosphate adsorption, the effects of modified biochar leachate on the germination of corn and rice seeds were examined. The results showed that phosphate adsorption by the modified biochar first increased and then decreased as the pyrolysis temperature increased, with modified biochar prepared at 800 °C showing the greatest adsorption. In addition, a comprehensive cost analysis showed that the best phosphate adsorption effect of modified biochar was achieved at a dosage of 0.10 g and a solution pH of 3. In contrast, the presence of competitive coexisting ions, Cl- , NO3 - , CO3 2- , and SO4 2- , reduced the phosphate adsorption capacity of the modified biochar. The adsorption kinetics results revealed that the process of phosphate adsorption by the modified biochar was more in line with the pseudo-second-order model and dominated by chemisorption. Moreover, the adsorption isotherm results indicated that the process was more in line with the Langmuir model and dominated by monomolecular layer adsorption, with a maximum adsorption of 217.54 mg/g. Subsequent seed germination tests showed that phosphate-adsorbed modified biochar leachate had no significant effect on the germination rate of corn seeds, whereas it improved the germination rate of rice seeds. Together, these results provide guidance for the application of modified biochar firstly as an adsorbent of phosphate and subsequently as a soil remediator.

Phosphate adsorption by amino acids intercalated calcium aluminum hydrotalcites: Kinetic, isothermal and mechanistic studies

Phosphorus is widely used in agriculture and industry. However, excessive phosphorus can cause eutrophication in aquatic environment. Therefore, the development of an simple, efficient and economical method for phosphate removal from wastewater is urgently needed. In this study, calcium aluminum layered double hydroxides (CaAl-LDHs) and six amino acid intercalated calcium aluminum layered double hydroxides (CaAl-amino acid-LDHs) was prepared by a facile method. In order to identify optimal amino acid, the adsorption performance of phosphate for six CaAl-amino acid-LDHs were comparatively studied. A high phosphate adsorption capacity were observed for l-Aspartic acid intercalated calcium aluminum layered double hydroxides (CaAl-Asp-LDHs). Experimental results showed that CaAl-Asp-LDHs can achieve phosphate anion adsorption capacity of 569.95 mg/g, which is significantly higher than that of CaAl-LDHs (236.86 mg/g) at pH 6.0 and favorable selectivity was observed when compared with other common anions. CaAl-Asp-LDHs exhibited a faster phosphate removal than that of CaAl-LDHs. The adsorption data of aqueous phosphate anion using CaAl-LDHs and CaAl-Asp-LDHs could be well described by the Langmuir isotherm model and pseudo-second order kinetics. Furthermore, based on the structural and morphological features, as well as fourier transform infrared spectrometer (FT-IR), diffraction of x-rays (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscope with energy dispersive x-ray spectroscopy (SEM-EDS) and element mapping, the phosphate adsorption mechanism on CaAl-Asp-LDHs involved the electrostatic attraction, hydrogen bonds, complexation and ion exchange. Compared with the performance of other phosphate sorbents in other reported, CaAl-Asp-LDHs has the highest adsorption value. The synthesized CaAl-Asp-LDHs, therefore, would be a promising environmentally friendly material for the efficient removal of phosphate from aquatic environments.

Simultaneous removal of phosphate and tetracycline using LaFeO3 functionalised magnetic biochar by obtained ultrasound-assisted sol–gel pyrolysis: Mechanisms and characterisation

Excessive phosphate and tetracycline (TC) contaminants pose a serious risk to human health and the ecological environment. As such exploring the simultaneous adsorption of phosphate and TC is garnering increasing attention. In this study, an efficient lanthanum ferrate magnetic biochar (FLBC) was synthesised from crab shells using an ultrasound-assisted sol–gel method to study its performance and mechanisms for phosphate and TC adsorption in aqueous solutions in mono/bis systems. According to the Langmuir model, the developed exhibited a maximum adsorption capacity of 65.62 mg/g for phosphate and 234.1 mg/g for TC (pH:7.0 ± 0.1, and 25 °C). Further, it exhibited high resistance to interference and pH suitability. In practical swine wastewater applications, whereby the concentrations of phosphate and TC are 37 and 19.97 mg/L, respectively, the proposed material demonstrated excellent performance. In addition, electrostatic adsorption, chemical precipitation and ligand exchange were noted to be the main mechanisms for phosphate adsorption by FLBC, whereas hydrogen bonding and π-π interaction were the main adsorption mechanisms for TC adsorption. Therefore, this study successfully prepared a novel and efficient adsorbent for phosphate and TC.

Simple synthesis of mesoporous ferrite materials as magnetic adsorbents for phosphate removal

AbstractMesoporous MFe2O4 materials (M = Mn, Cu, and Co) as magnetic adsorbents for phosphate removal were synthesized by a simple coprecipitation method without annealing at high temperatures. Several techniques, including powder X‐ray diffraction, field emission electron scanning microscopy, nitrogen adsorption‐desorption and vibrating sample magnetometry were used to characterize the samples. The effects of M2+ ions on their point of zero charge and their phosphate adsorption capacity were investigated. All three samples consist of nanosized particles with cubic spinel structure and ferromagnetic properties, which allows them to be easily separated from aqueous effluents using a magnet. According to the batch experiments, the adsorption isotherms and the adsorption kinetics for these mesoporous materials are well fitted with the nonlinear Langmuir model and the nonlinear pseudo‐second‐order model, respectively. Among them, CuFe2O4 powder showed the best phosphate adsorption performance with the maximum P adsorption capacity of 27.49 mgP g‐1, which can be assigned to the highest surface area and the high pH value at its point of zero charge.

Screening optimal preparation conditions of low-cost metal-modified biochar for phosphate adsorption and unraveling their influence on adsorption performance

Abundant novel metal-modified biochars have been synthesized for phosphate removal under various preparation conditions, but optimal biochar adsorbents with low cost and high removal performance for application in real scenarios are still largely scarce. In this study, the optimal preparation conditions for metal-modified biochar were screened stepwise by determining their phosphate adsorption performance and cost with frequently used preparation conditions, including different feedstocks (total 7 biomass residues), pyrolysis temperatures (400 °C and 600 °C), modification methods (impregnation and coprecipitation), and modifying metals (Fe/La/Mg). Furthermore, the influences of preparation conditions on adsorption capacity and mechanisms were interpreted via multiple characterization methods by compared with the optimal preparation conditions. The results showed that Mg coprecipitated peanut shell biochar at 600 °C (denoted PS–600–C–Mg) was the optimal phosphate adsorbent with a maximum adsorption capacity of 50.58 mg g−1 and a cost benefit ratio (CBR) of 3.24 × 104 RMB t−1 based on adsorption capacity and cost‒benefit analysis via Monte Carlo simulations. The different mesoporous (2–50 nm) and macroporous structures (>50 nm), which were generated under various preparation conditions and favored the development of metal (hydr)oxides, could explain the greater adsorption capacity of this optimal biochar. Furthermore, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), zeta potential and Fourier transform infrared spectroscopy (FTIR) spectra jointly revealed that modification methods and modifying metal types changed adsorption mechanisms with phosphate significantly. The dominant role of electrostatic force in the adsorption of the optimal biochar towards phosphate was interpreted mainly by the unchanged FTIR spectra, negative surface charge, and further confirmed by the interaction region indicator (IRI) and localized orbital locator (LOL) at the molecular level by using density functional theory (DFT).

Adsorption Performance and Mechanism of Phosphate in Water by Magnesium Oxide-Corncob Biochar

Adsorption Performance and Mechanism of Phosphate in Water by Magnesium Oxide-Corncob Biochar

Porous La2O2CO3 derived from solvent-guided metal-organic frameworks for high-efficient phosphorus removal

La-based materials have garnered considerable attention as potential adsorbents for phosphate removal because they capture phosphate with high affinity, producing an ultralow phosphorous-concentration output. Herein, La-based metal–organic frameworks (La–MOFs, La-1,3,5-benzentricarboxylate) with tunable structures were fabricated by regulating the coordination solvent environment, which largely determines both the pore structure and chemical components of their corresponding La2O2CO3 derivatives and the phosphate adsorption performance. A porous La2O2CO3 derivative (W–D T500) derived from the water/N,N-dimethylformamide (DMF) guided La–MOF showed abundant mesopores and a high surface area, because the pore-opening degree under high-temperature pyrolysis is higher in W–D T500 than in the La2O2CO3 derivative obtained from the water/ethanol solvent–guided La–MOF. W–D T500 also had higher La (78.3%) and carbonate contents of the crystal structure owing to the higher efficiency of carbon conversion to carbonate-oxides in W–D T500. Consequently, the porous La2O2CO3 derivative W–D T500 exhibited superior phosphate adsorption capacity (91.6 mg P/g), high adsorption selectivity, and excellent recycling performance. Phosphate was attached to the La2O2CO3 adsorbents via a ligand-exchange mechanism between phosphate and CO32−/–OH. This study provides a solvent guidance strategy to construct functional La–MOFs and La2O2CO3 derivatives for excellent phosphate removal.