Adsorption of phosphate from aqueous solutions and sewage using zirconium loaded okara (ZLO): Fixed-bed column study

Nutrients recovery from livestock wastewater by batch and gas bubble-column studies with biochar, nano-composite material, and ammonium magnesium phosphate hydrate

The breeding of livestock raises substantial environmental concerns, especially the efficient management of nutrients and pollution. This research is designed to assess the potency of char and modified char in diluting nutrient concentrations in livestock wastewater. The characteristics of graphene oxide, struvite, and calcium-modified char were inspected, defining their efficacy in both batch and bed-column investigations of nutrient sorption. Various factors, including sorption capacity, time of contact, ion levels, a decrease in ion levels over time, and sorption kinetics, have been considered, along with their appropriateness for respective models. The first evaluation of the options concluded that 600 °C char was better since it exhibited higher removal efficiency. Modified char sorption data at 600 °C was used to adjust the models "PSOM, Langmuir", and "Thomas". The models were applied to both batch and bed-column experiments. The maximum phosphate sorption was 110.8 mg/g, 85.73 mg/g, and 82.46 mg/g for B-GO, B-S, and B-C modified chars respectively, in the batch experiments. The highest phosphate sorption in column experiments, at a flow rate of 400 μl/min, was 51.23 mg per 10 g of sorbent. This corresponds to a sorption rate of 5.123 mg/g. B-GO and B-S modified chars showed higher sorption capacities; this was observed in both the batch and bed-column studies. This displayed the capability of graphene oxide and struvite-modified chars for efficient ion and nutrient uptake, whether in single or multi-ion environments, making them a very good candidate for nutrient filtration in livestock wastewater treatment. Additionally, B-GO char enhanced the sorption of phosphate, resulting in augmented seed germination and seedling growth. These results reveal that B-GO char can be used as a possible substitute for chemical fertilizers.

Recycling and reuse of waste agricultural plastics with hydrothermal pretreatment and low-temperature pyrolysis method

Recycling and reuse of agricultural plastics is an urgent worldwide issue. In this work, it is shown that low-density polyethylene (PE) typically used in mulch films can be converted into high-capacity P and N adsorbents through a two-step method that uses hydrothermal pretreatment (180 °C, 24 h) followed by pyrolysis at 500 °C with Ca(OH)2 additive. CaPE@HC500 materials prepared with the proposed two-step method were found to have high adsorption capacities for phosphate (263.6 mg/g) and nitrogen (200.7 mg/g) over wide ranges of pH (3-11). Dynamic adsorption of phosphate by CaPE@HC500 material in a packed-bed had a half-time breakthrough of 210 min indicating the feasibility of continuous systems. Material stability, cost, environmental-friendliness, and recyclability of the CaPE@HC500 material were determined to be superior to literature-proposed Ca-containing adsorbents. The two-step method for converting waste agricultural plastic mulch films into adsorbents is robust and highly-applicable to industrial settings.

An overview on the key advantages and limitations of batch and dynamic modes of biosorption of metal ions

Water purification using adsorption is a crucial process for maintaining human life and preserving the environment. Batch and dynamic adsorption modes are two types of water purification processes that are commonly used in various countries due to their simplicity and feasibility on an industrial scale. However, it is important to understand the advantages and limitations of these two adsorption modes in industrial applications. Also, the possibility of using batch mode in industrial scale was scrutinized, along with the necessity of using dynamic mode in such applications. In addition, the reasons for the necessity of performing batch adsorption studies before starting the treatment on an industrial scale were mentioned and discussed. In fact, this review article attempts to throw light on these subjects by comparing the biosorption efficiency of some metals on utilized biosorbents, using both batch and fixed-bed (column) adsorption modes. The comparison is based on the effectiveness of the two processes and the mechanisms involved in the treatment. Parameters such as biosorption capacity, percentage removal, and isotherm models for both batch and column (fixed bed) studies are compared. The article also explains thermodynamic and kinetic models for batch adsorption and discusses breakthrough evaluations in adsorptive column systems. The review highlights the benefits of using convenient batch-wise biosorption in lab-scale studies and the key advantages of column biosorption in industrial applications.

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.

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 (1-9 mg L-1), initial ion concentration (1-9 mg L-1), pH value (2-10), and oak-nZVI dosage (2-16 mL). 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.

Thermally-activated gelatin-chitosan-MOF hybrid aerogels for efficient removal of ibuprofen and naproxen

Nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the most frequently used drugs and have been frequently detected in aquatic environments. This paper demonstrates a thermally-activated gelatin-chitosan and amine-functionalized metal-organic framework (UiO-66-NH2) aerogel (CGC-MOF), which was successfully synthesized for the efficient removal of ibuprofen (IBP) and naproxen (NPX). Various characterization tools were used to systematically analyze the microstructure and physicochemical properties of the synthesized aerogel. In addition, the effect of key reaction parameters as well as batch and continuous-flow fixed-bed column experiments were carried out to elucidate the adsorption process. Several functional groups in the biopolymer network, combined with excellent MOF properties, synergistically couple to form an adsorbent with great performance. The mesoporous aerogel activated at 200 °C (CGC-MOF200) exhibited a high specific surface area (819.6 m2/g) that is valuable in providing abundant adsorption active sites that facilitate the efficient adsorption of IBP and NPX. CGC-MOF200 exhibited an excellent removal of IBP and NPX, accounting to 99.28 % and 96.39 %, respectively. The adsorption process followed the pseudo-second-order kinetics and the Freundlich isotherm models, suggesting heterogeneous and chemisorption adsorption processes. Overall, this work provides new and valuable insights into the development of a promising biopolymer-MOF composite aerogel for environmental remediation.

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.

Phosphorus removal from wastewater using Ca-modified attapulgite: Fixed-bed column performance and breakthrough curves analysis

The adsorbent calcium-modified attapulgite (Ca-GAT) prepared by calcium chloride modification and high temperature treatment (700 °C) has proved to remove phosphorus in low-concentration phosphorus wastewater in batch adsorption experiments. Dynamic adsorption performance and industrial application potential still need further determination. This study explored the effects of various parameters on the dynamic phosphorus adsorption, including initial phosphate concentration (2-10 mg/L), flow rate (1-3 mL/min) and adsorption bed height (2-6 cm). Phosphorus adsorption ability improved and the breakthrough time increased with the increase of bed height, flow rate, and a decrease in initial phosphorus concentration. Breakthrough curves fitted four models, the Adams-Bohart, Thomas, Yoon-Nelson and Bed depth service time (BDST). The maximum adsorption amount determined by the Thomas model obtained 13.477 mg/g. The saturated fixed-bed column were regenerated with NaOH, NaOH + NaCl and HCl, among which 0.5 mol/L NaOH had the best regeneration effect. During the utilization of a large fixed-bed to treat the actual membrane bioreactor (MBR) effluent, the breakthrough point (0.5 mg/L) was obtained after 177 h. These results implied that Ca-GAT had an application potential for the treatment of low-concentration phosphorus wastewater (2 mg/L).

Removal of copper ions from alembic cachaça using agro-industrial residues as biosorbents

Cachaça is a typical Brazilian distilled beverage made from fermented sugarcane juice. The copper levels in alembic cachaça are of great concern among producers, and the removal of this contaminant is important for the quality of the product. The present study aimed to remove copper ions from alembic cachaça by adsorption. Sugarcane bagasse, okara, Moringa oleifera Lam., three different types of zeolites, and two types of commercial charcoal were tested as biosorbents. The heat-treated sugarcane bagasse removed 100% of the copper present in a cachaça sample, while other low-cost natural adsorbents had close to 50% removal as was observed for M. oleifera seeds and okara. All adsorbents had porous and fibrous structures, favorable to adsorption. A kinetic study showed that a pseudo-second-order model was appropriate, with equilibrium times of 15 h for heat-treated sugarcane bagasse, okara, and M. oleifera seeds used as adsorbents. The Langmuir model better fitted the experimental data, indicating monolayer adsorption. The maximum adsorption capacity was 17.00, 0.77, and 5.33 mg of Cu g^-1 for the heat-treated sugarcane bagasse, M. oleifera seeds, and okara, respectively. The results presented here are promising indicating three agro-industrial residues were favorable to the adsorption of copper ions from alembic cachaça.

Easily synthesized mesoporous aluminum phosphate for the enhanced adsorption performance of U(VI) from aqueous solution

High-yield selective adsorbents and suitable modification methods are both significant for the efficient treatment of U-contaminated wastewater. In this work, a rich-mesoporous aluminum phosphate adsorbent (APO-10) was synthesized by simply increasing the mass of reactants under a fixed solvent volume. After increasing the mass of reactants ten times, APO-10 has the added defect level, the increased specific surface area, and mesoporous structure, and the increased number and enhanced adsorption ability of adsorption active sites (phosphorus-oxygen groups) on the surface, resulting in an enhanced adsorption performance of U(VI) in various environmental conditions. Its ultrahigh adsorption capacity calculated by the Langmuir model can reach 826.44 mg g^-1 at pH = 5.5 and T = 298 K. Its crystal structure did not change after adsorption and remained at 584.40 mg g^-1 after 6 cycles. Additionally, APO-10 shows an excellent uranium-selectivity over 68% from a mixed aqueous solution and has excellent applicability in the acidic and alkaline environment based on dynamic adsorption and desorption column experiments. This study not only provides a high-yield efficient selective adsorbent (APO-10) with excellent anti-radiation structure stability for the treatment of radioactive contamination but also provides a feasible modification method by simply increasing the mass of reactants.

Removal of phosphate at low concentration from water by porous PVA/Al2O3 composites

The porous polyvinyl alcohol (PVA)/Al₂O₃ composite by supporting activated alumina on the cross-linked network of PVA has been successfully prepared and its property for the removal of phosphate in aqueous solution was also evaluated. The structure of the PVA/Al₂O₃ was examined by scanning electron microscopy. It showed that the activated alumina particles with an average size of 1 μm were evenly dispersed and fixed in the cross-linked network structure of PVA. The effects of adsorption time, solution temperature, pH, initial concentration of phosphate, Al₂O₃ loading rate, dosage and coexisting ions on the phosphate removal were further studied. The results showed that the highest removal phosphate efficiency of 95% can be obtained with the Al₂O₃ loading rate of PVA/Al₂O₃ being 60 wt.% at pH of 4 at 30 °C. The maximum adsorption capacities of PO43- by PVA/Al₂O₃ suggested by the Langmuir isothermal model was 10.12 mg/g. The adsorption process of phosphate can be fit well with a pseudo-second-order model (R² = 0.9900). The PVA/Al₂O₃ composite exhibited a high selective adsorption of phosphate in the presence of commonly coexisting anions except the obvious effect of CO32- in water. Meanwhile, the PVA/Al₂O₃ composite can be easily separated and recovered due to the granulation of adsorbent. PVA/Al₂O₃ composite also shows the excellent properties of regeneration and recycling use with the removal efficiency of phosphate was 88.93%, 88.38% and 94.34% after three cycles, respectively. It can be proposed that the PVA/Al₂O₃ composite is a promising recyclable adsorbent for removing phosphate at low concentration from aqueous solution.

Development of porous material via chitosan-based Pickering medium internal phase emulsion for efficient adsorption of Rb+, Cs+ and Sr2

The radioactive Rb⁺, Cs⁺ and Sr²⁺ have serious threat for the aquatic life and human health, its removal has been granted increasing concern. Hence the adsorbent with excellent adsorption performance and favourable reusability is strongly demanded. This work prepared a novel porous polymer of chitosan-g-polyacrylamide (CTS-g-PAM) by grafting the acrylamide (AM) onto the chitosan (CTS) with sufficient pore structure via an eco-friendly surfactant-free (corn oil)-in-water Pickering medium internal phase emulsion (O/W Pickering MIPE), solely stabilized by CTS. Interestingly, its pore structure could be tuned by varying the emulsion character via changing the molecular weight and concentration of CTS, as well as the pH values. Due to the abundant -COO^- and -NH₂ functional groups in the porous material of CTS-g-PAM, the high adsorption capacities of 195.43, 237.44 and 185.63 mg/g for Rb⁺, Cs⁺ and Sr²⁺ could be reached within 40, 30 and 20 min, respectively. Moreover, the CTS-g-PAM had excellent regeneration ability and reusability. Herein, we provided a feasible and low-cost pathway for preparation of the porous adsorbent with tunable porous structure for adsorption and separation application.

Preparation and Adsorption Properties of Soybean Dreg/Hydrocalumite Composites

The application of biomass-based composites in the field of adsorption has attracted extensive attention. Herein, soybean dreg/hydrocalumite composites were prepared by in situ self-assembly from soybean dregs and applied to the adsorption of Congo Red (CR). The composites were characterized by scanning electron microscopy, X-ray diffraction, Fourier infrared spectroscopy, and N₂ physical adsorption-desorption. The results showed that the adsorption property of soybean dregs/hydrocalumite for CR was better than that of soybean dregs or hydrocalumite. Effects of preparation and adsorption conditions on the adsorption of CR by soybean dregs/hydrocalumite were also investigated. The removal rate of soybean dregs/hydrocalumite (30%BD-LDH) prepared under the optimized conditions reached 97.4% with a 486.8 mg·g^-1 adsorption capacity. Also, the adsorption capacity of 30%BD-LDH was about 2.4 times and 3.0 times that of hydrocalumite and soybean dregs, respectively. In addition, the adsorption process of CR by 30%BD-LDH was more in line with the pseudo-second-order kinetic and Langmuir isothermal models.

Fixed-Bed Column Technique for the Removal of Phosphate from Water Using Leftover Coal

The excessive discharge of phosphate from anthropogenic activities is a primary cause for the eutrophication of aquatic habitats. Several methodologies have been tested for the removal of phosphate from aqueous solutions, and adsorption in a flow-through reactor is an effective mechanism to reduce the nutrient loading of water. This research aimed to investigate the adsorption potential of leftover coal material to remove phosphate from a solution by using continuous flow fixed-bed column, and analyzes the obtained breakthrough curves. A series of column tests were performed to determine the phosphorus breakthrough characteristics by varying operational design parameters such as adsorbent bed height (5 to 8 cm), influent phosphate concentration (10–25 mg/L), and influent flow rate (1–2 mL/min). The amorphous and crystalline property of leftover coal material was studied using XRD technology. The FT-IR spectrum confirmed the interaction of adsorption sites with phosphate ions. Breakthrough time decreased with increasing flow rate and influent phosphate concentration, but increased with increasing adsorbent bed height. Breakthrough-curve analysis showed that phosphate adsorption onto the leftover coal material was most effective at a flow rate of 1 mL/min, influent phosphate concentration of 25 mg/L, and at a bed height of 8 cm. The maximal total phosphate adsorbed onto the coal material’s surface was 243 mg/kg adsorbent. The Adams–Bohart model depicted the experimental breakthrough curve well, and overall performed better than the Thomas and Yoon–Nelson models did, with correlation values (R²) ranging from 0.92 to 0.98. Lastly, leftover coal could be used in the purification of phosphorus-laden water, and the Adams–Bohart model can be employed to design filter units at a technical scale.

Comparative research on selective adsorption of Pb(II) by biosorbents prepared by two kinds of modifying waste biomass: Highly-efficient performance, application and mechanism

In this study, we used xanthate to modify two waste biomass materials (corn cob and chestnut shell) and prepared them as biosorbents in one step for effectively removing Pb(II) from aqueous solutions containing only Pb(II) or Pb(II), Cu(II) and Cd(II). The two biosorbents were characterized by SEM, EDS, FTIR and Zeta potential analysis, and the results of the characterization were used to explore the adsorption mechanism of Pb(II) on biosorbents. We compare the Pb(II) removal ability of the two biosorbents and the investigated factors that affect Pb(II) removal. The results show that the adsorption capacity of xanthate modified corn cob (X-CC) and xanthate modified chestnut shell (X-CS) for Pb(II) is related to pH, reaction time, temperature and initial concentrations of both adsorbent and adsorbate. The adsorption of Pb(II) on X-CC and X-CS follows Langmuir isotherm equation and quasi-secondary kinetic equation, and their fitted q_m values are 166.39 and 124.84 mg g^-1, respectively. The analysis shows that the biosorbent has high selectivity to Pb(II) rather than Cu(II) and Cd(II), and still maintains a high removal rate of Pb(II) in actual wastewater. The biosorbents remove metal ions mainly through ion exchange reaction and the functional group in the material complexes with the metal to form micro-precipitation. The high adsorption capacity in aqueous solution and low costs in the manufacturing process of the present biosorbents ensure that they have great potential in practical applications for treating heavy-metal contaminated surface water.

Lignin-based nanoparticles for recovery and separation of phosphate and reused as renewable magnetic fertilizers

In this work, magnetic lignin-based nanoparticles (M/ALFe) were developed and used to adsorb phosphorus to obtain phosphorus-saturated nanoparticles (M/ALFeP). The nanoparticles were then used as renewable slow-release compound fertilizers. First, aminated lignin was synthesized via Mannich reaction, and then Fe₃O₄ nanoparticles were loaded and Fe³⁺ was chelated on the aminated lignin to prepare M/ALFe. Finally, M/ALFeP were obtained after adsorption of phosphorus. The effects of nanoparticle dosage, solution pH and adsorption time on adsorption efficiency were determined. Adsorption isotherm and adsorption kinetics results suggested that the adsorption was coincided with the pseudo-second-order and Temkin model, respectively. The cumulative release of Fe and phosphorus from M/ALFeP increased gradually and reached to 67.2% and 69.1% in soil after 30 days, respectively. After the release of nutrients, M/ALFeP can be separated by a magnet with a high recovery ratio from water or soil and regenerated for phosphate recovery again. Therefore, the magnetic lignin-based nanoparticles have a promising application potential as an efficiently separated and renewable nanomaterial for removal of low concentration phosphate in wastewater treatment and as a slow-release fertilizer in sustainable agriculture.

Efficient Adsorption of Tetracycline from Aqueous Solutions by Modified Alginate Beads after the Removal of Cu(II) Ions

This work dealt with a potential and effective method to reuse modified alginate beads after the removal of Cu(II) ions for efficient adsorption of tetracycline (TC) from aqueous solutions. The modified alginate beads were fabricated by a polyacrylamide (PAM) network interpenetrated in alginate-Ca2+ network (PAM/CA) decorated with polyethylene glycol as a pore-forming agent. The porous PAM/CA was characterized using scanning electron microscopy, Brunauer-Emmett-Teller, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analysis. The adsorption kinetics, isotherms, adsorption stability, and reusability studies of the adsorbent toward Cu(II) ions were scrutinized. The column performance of porous PAM/CA was tested with Cu(II)-containing electroplating wastewater. After Cu(II) adsorption, the Cu(II)-adsorbed PAM/CA (PAM/CA@Cu) was applied to remove TC from aqueous solutions without any regeneration process. The effects of pH, initial TC concentration, ionic strength, and coexisting ions on the adsorption were also discussed in detail. Compared with many reported adsorbents, the PAM/CA@Cu exhibited an excellent adsorption performance toward TC with a maximum adsorption capacity of 356.57 mg/g predicted by the Langmuir model at pH 5.0 and 30 °C with the absence of coexisting ions. The possible adsorption mechanism of TC onto the PAM/CA@Cu was revealed.

Application of iron [Fe(0)]-rich substrate as a novel capping material for efficient simultaneous remediation of contaminated sediments and the overlying water body

Release of contaminants from sediments has been one of the main pollution sources causing eutrophication and malodorous black of ponds. In this study, an iron-rich substrate (IRS) was developed based on iron‑carbon micro-electrolysis and applied for simultaneous sediments and overlying water remediation. IRS obtained high ammonia and phosphate adsorption capacities (Langmuir isotherm) of 13.02 and 18.12 mg·kg^-1, respectively. In the 90-day long-term remediation, IRS reduced NH₄⁺-N, PO₄^3--P, organic-N, organic-P, TN and TP in overlying water by 48.6%, 97.9%, 34.2%, 67.1%, 53.2% and 90.4%, respectively. In sediments, IRS reduced NO₃^--N, NH₄⁺-N and organic-N by 98.5%, 26.5% and 6.3%, respectively. The unstable P-compounds (i.e., organic-P, Ca-bounded-P and labile-P) were effectively transferred (20.1%, 54.3% and 98.2%, respectively) into inert P-compounds (i.e., Fe-bounded-P and residual-P). Meanwhile, flux rates of nitrogen and phosphorus from sediments to overlying water were reduced from 7.02 to 4.92 mg·m^-2·d^-1 (by 29.9%) and from 7.42 to 2.21 mg·m^-2·d^-1 (by 70.2%), respectively. Due to micro-electrolysis, Fe²⁺/Fe³⁺/[H] were in-situ generated from IRS and NO₃^--N was effectively reduced. Additionally, the generation of O₂^· was promoted by Fe²⁺/[H] and strengthened the NH₄⁺-N, organic-N/P oxidation. Fe³⁺ enhanced the immobilization of PO₄^3- (e.g., as FePO₄·H₂O and Fe_nPO₄(OH)_3n-3). The released Fe²⁺/Fe³⁺ from IRS were finally stabilized as poorly reactive sheet silicate (PRS)-Fe and magnetite-Fe in the sediments and hardly showed side effect to sediments and water body. The developed IRS obtained advantages of high efficiency, ecologically safe and cost-effective in contaminated sediments and overlying water remediation.

Development of polyaminated chitosan-zirconium(IV) complex bead adsorbent for highly efficient removal and recovery of phosphorus in aqueous solutions

The aim of this work is to examine the adsorption performance and mechanism of phosphorus (P) onto polyethyene polyamine (PEPA) grafted chitosan-zirconium(IV) composite beads (CS-Zr-PEPA) from aqueous solutions. The morphology, functional groups, and surface area of the CS-Zr-PEPA beads were characterized by SEM, FTIR, and BET analysis. Batch adsorption experiments were conducted via different operating parameters such as solution pH, initial phosphate concentration, co-existing anions and temperature. The adsorption kinetics, equilibrium isotherms and adsorption stability of the adsorbent were scrutinized. In comparison with other CS-based beads, the CS-Zr-PEPA had a greater affinity towards P and exhibited a maximum adsorption capacity of 103.96 mg-P/g predicted by Langmuir mode. The reusability studies of CS-Zr-PEPA beads were carried out. The CS-Zr-PEPA beads exhibit preferable sequestration of P through specific interactions, as further demonstrated by studying physicochemical characteristics of the virgin beads and P-adsorbed beads using X-ray photoelectron spectroscopy (XPS). The column performance of CS-Zr-PEPA beads was tested with P-containing wastewater. Results indicated that the developed CS-Zr-PEPA composite beads could be utilized as a promising adsorbent for effective removal and recovery of P from water and wastewater.

Performance analysis of hydrated Zr(IV) oxide nanoparticle-impregnated anion exchange resin for selective phosphate removal

The superior removal selectivity of hydrated zirconium oxide nanoparticle-impregnated porous anion exchange resin (ZAE) highlights its use as phosphate removal adsorbent. However, most research examines selective phosphate removal performance using randomly determined single content of hydrated zirconium oxide, and thus the use of the ZAE in real applications remains limited. Therefore, this study aimed to investigate the selective phosphate removal performance of ZAE with different content of hydrated zirconium oxide nanoparticle (HZO NP, represented by zirconium content) by considering various conditions. A molybdate intermediate method was devised to fabricate ZAE with high loaded HZO by weakening the Donnan exclusion to HZO precursors produced from the fixed positively charged host. Consequently, the resultant ZAE was characterized by 17.8 wt% of zirconium. ZAE exhibited an increased selectivity to phosphate against competing ions in the synthetic and simulated real water matrices for both batch and fixed-bed modes as the zirconium content of ZAE increased. High performance was retained, and regeneration led to possible reusability. The linear correlation between selective phosphate removal performances and zirconium content indicates that the zirconium content is a fundamental factor determining the ZAE phosphate adsorption removal. The HZO NPs within ZAE slow adsorption kinetics by blocking AE pores and provide specific adsorption sites for phosphate removal by inner-sphere complexation.

Phosphate adsorption performance and mechanisms by nanoporous biochar-iron oxides from aqueous solutions

To evaluate the adsorption mechanism and performance of phosphate onto the composite of low-cost biochar and iron oxide, four biochar-iron oxides, namely biochar-magnetite (BC-M), biochar-ferrihydrite (BC-F), biochar-goethite (BC-G), and biochar-hematite (BC-H), were prepared by fabricating iron oxide to porous biochar. The biochar-iron oxides had huge surface areas of 691-864 m²/g and average pore diameters of 3.4-4.0 nm. Based on the characterization analysis of FTIR, XRD, XPS, and zeta potential, the interactions of electrostatic attraction, ligand exchange, and deposition dominated the phosphate adsorption onto biochar-iron oxides. The maximum adsorption capacity of phosphate followed the order of BC-G > BC-F > BC-H > BC-M. The isotherm data of BC-M and BC-H were well fitted by the Langmuir and Freundlich models, while those of BC-G and BC-F followed the Langmuir model. In addition, BC-M, BC-F, BC-G, and BC-H owned excellent regeneration ability and adsorption performance in practical (simulated) wastewater environment. Then the biochar-iron oxides exerted extensive and satisfactory prospect in wastewater remediation and recycling application in soil.

Phosphorus removal from secondary wastewater effluent using copper smelter slag

This study investigated the use of copper smelter slag for the removal of phosphorus from secondary wastewater effluent through batch tests. The media was physically and chemically characterized and showed presence of Fe2O3 (45.22%), SiO2 (14.98%), Al2O3 (3.21%), CaO (1.99%), SO3 (1.77%) and MgO (1.33%). Scanning electron microscopy monographs revealed smooth and flat surface and no heterogeneity on the surface of the slag with visible micro pores before the experiment and less visible after the experiment. The point of zero charge of the media was 5.0. Equilibrium was reached after 4 h at 29.5 ± 0.71% phosphorus removal efficiency and media dosage of 0.4/100 mL. The kinetic data was best described by Pseudo second order equation. More than one mechanisms were involved in the adsorption of phosphorus onto copper smelter slag as suggested by multi-linearity of intra particle diffusion model. Ninety seven percent (97.5 ± 0.0%) removal efficiency was achieved at an equilibrium dosage of 160 gL-1. The equilibrium isotherm was described better by Langmuir equation with observed maximum adsorption capacity of 0.16 mg P g-1 media and the experimental maximum adsorption capacity was 0.26 mg P g-1 media. Regeneration studies showed low performance with maximum efficiency of 11.7% revealed during the first regeneration trial therefore low practical benefits. Copper smelter slag is a poor adsorbent for phosphorus and further studies on the media should be conducted.

Low-cost chitosan-calcite adsorbent development for potential phosphate removal and recovery from wastewater effluent

Phosphorous (P) recovery from wastewater will become increasingly vital in the future as terrestrial rock phosphate deposits are expended. Effective management of P as a critical resource will require new techniques to recover P from wastewater, ideally in a form that can be used in agriculture as fertiliser. In this study, batch and fixed-bed column conditions were tested using a novel KOH deacetylated calcite-chitosan based adsorbent (CCM) for P removal from aqueous solutions and wastewater effluents. The unique characteristics of this adsorbent as a phosphate adsorbent were the result of rich surface functionality (amine and sulphur functional groups of the chitosan and proteins) and the CaCO₃ content (providing donor ligands; and additionally beneficial if the material were used as fertiliser, buffering soil acidification caused by nitrogen application). The maximum P adsorption capacity was determined to be 21.36 mgP/g (at 22 °C) and the endodermic process reached equilibrium after 120 min. The experimental data was best described using a Langmuir isotherm and a pseudo-second order kinetic model. The diffusion kinetic analysis highlighted the importance of both film and intraparticle mass-transport. Material characterisation suggested that the adsorption process involved interactions between P and functional groups (mostly -NH₃⁺) due to electrostatic interaction on the chitosan chain or involved ligand exchange with CO₃^2-. Analysis of materials using X-Ray Powder Diffraction (XRPD) and Thermogravimetric Analysis (TGA) indicated a microprecipitation-type mechanism may occur through the formation of hydroxylapatite (Ca₅(PO₄)₃(OH)). Desorption studies demonstrated that the P-laden CCM (derived from crab carapace) had the potential to be reused in soil amendment as a slow-release P fertiliser. The effects of different operating parameters were explored in a fixed-bed column, and the experimental data fitted well to the Clark model (R² = 0.99). The CCM also showed excellent P adsorption potential from secondary and final wastewater effluent in dynamic conditions, even at low P concentrations. Finally, a scale-up approach with cost analysis was used to evaluate the price and parameters needed for a potential large-scale P recovery system using this adsorbent.

Phosphate recovery with granular acid-activated neutralized red mud: Fixed-bed column performance and breakthrough curve modelling

Granular acid-activated neutralized red mud (AaN-RM) has been successfully prepared with good chemical stability and physical strength. However, its potential for industrial application remains unknown. Therefore, the performance of granular AaN-RM for phosphate recovery in a fixed-bed column was investigated. The results demonstrated that the phosphate adsorption performance of granular AaN-RM in a fixed-bed column was affected by various operational parameters, such as the bed depth, flow rate, initial solution pH and initial phosphate concentration. With the optimal empty-bed contact time (EBCT) of 24.27 min, the number of processed bed volumes and the phosphate adsorption capacity reached 496.95 and 84.80 mg/g, respectively. Then, the saturated fixed-bed column could be effectively regenerated with a 0.5 mol/L HCl solution. The desorption efficiency remained as high as 83.45% with a low weight loss of 3.57% in the fifth regeneration cycle. In addition, breakthrough curve modelling showed that a 5-9-1 feed-forward artificial neural network (ANN) could be effectively applied for the optimization of the fixed-bed adsorption system; the coefficient of determination (R²) and the root mean square error (RMSE) evaluated on the validation-testing data were 0.9987 and 0.0183, respectively. Therefore, granular AaN-RM fixed-bed adsorption exhibits promising potential for phosphate removal and recovery from polluted water.

Effective phosphorus removal using chitosan/Ca-organically modified montmorillonite beads in batch and fixed-bed column studies

In this study, phosphorus removal from aqueous solution was investigated using chitosan/Ca-organically modified montmorillonite (chitosan/Ca-OMMT) beads in batch and fixed-bed column systems. The XPS spectra confirmed that the calcium ions on the surface of the beads play a dominant role in capturing phosphate ions through surface complexation. The batch adsorption experimental data were fitted with pseudo-second-order kinetics and the Langmuir isotherm. The maximum adsorption capacity of the chitosan/Ca-OMMT beads was found to be 76.15 mg/g at an initial phosphate concentration of 100 mg/L at 25 °C. High phosphate uptake is achieved over the wide pH range 3-11, as well as in the presence of competing anions such as Cl^-, NO₃^-, SO₄^2-, and HCO₃^-. Furthermore, the chitosan/Ca-OMMT beads can be easily regenerated using 0.1 mol/L NaOH as a desorption agent with more than 83.97% adsorption capacity remaining after five adsorption/desorption cycles. The Thomas, Yoon-Nelson, and Adams-Bohart models were applied to the experimental data to predict the breakthrough curves using non-linear regression; the Yoon-Nelson model showing the best agreement with the breakthrough curves. These findings demonstrate that chitosan/Ca-OMMT beads can be used as a cost-effective and environment-friendly adsorbent for the removal of phosphate from wastewater.

The adsorption of phosphate using a magnesia-pullulan composite: kinetics, equilibrium, and column tests

A magnesia-pullulan (MgOP) composite has been developed to remove phosphate from a synthetic solution. In the present study, the removal of phosphate by MgOP was evaluated in both a batch and dynamic system. The batch experiments investigated the initial pH effect on the phosphate removal efficiency from pH 3 to 12 and the effect of co-existing anions. In addition, the adsorption isotherms, thermodynamics, and kinetics were also investigated. The results from the batch experiments indicate that MgOP has encouraging performance for the adsorption of phosphate, while the initial pH value (3-12) had a negligible influence on the phosphate removal efficiency. Analysis of the adsorption thermodynamics demonstrated that the phosphate removal process was endothermic and spontaneous. Investigations into the dynamics of the phosphate removal process were carried out using a fixed bed of MgOP, and the resulting breakthrough curves were used to describe the column phosphate adsorption process at various bed masses, volumetric flow rates, influent phosphate concentrations, reaction temperatures, and inlet pH values. The results suggest that the adsorption of phosphate on MgOP was improved using an increased bed mass, while the reaction temperature did not significantly affect the performance of the MgOP bed during the phosphate removal process. Furthermore, higher influent phosphate concentrations were beneficial towards increasing the column adsorption capacity for phosphate. Several mathematic models, including the Adams-Bohart, Wolboska, Yoon-Nelson, and Thomas models, were employed to fit the fixed-bed data. In addition, the effluent concentration of magnesium ions was measured and the regeneration of MgOP investigated.

Effect of phosphate concentration, anions, heavy metals, and organic matter on phosphate adsorption from wastewater using anodized iron oxide nanoflakes

Phosphorus is a necessary nutrient for the growth and survival of living beings. Nevertheless, an oversupply of phosphorus in wastewater results in eutrophication. Therefore, its removal from wastewater is important. However, coexisting components, such as anions, heavy metals, and organic matter, might inhibit the phosphate-adsorption mechanism by competing for the active surface sites of the adsorbent. In this study, iron oxide nanoflakes (INFs) were fabricated on iron foil via anodization. The rate of phosphate adsorption from wastewater onto INFs in the presence of three different coexisting components-anions, heavy metals, and organic matter-was evaluated. The morphology of the INFs was analyzed by X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. The phosphate adsorption equilibrium time using INFs was found to be 1 h. The Elovich model (R² > 0.99) and the Langmuir model (R² >0.95) respectively provided the best description of the adsorption kinetics and isotherm, suggesting the chemisorption nature of adsorption. The estimated adsorption capacity of the INFs was 21.5 mg-P g^-1. The effect of anions (chloride, sulfate, nitrate, and carbonate) and heavy metals (Cd, As, Cr, and Pb) was studied at three different molar ratios (0.5:1, 1:1, and 1.5:1). The effect of different types of organic matter, such as citric acid, humic acid, and oxalic acid at concentrations of 100 and 200 mg L^-1, was also examined. In five regeneration cycles, the total amount of phosphate adsorbed and desorbed, and the recovery percentage were 6.51 mg-P g^-1, 5.16 mg-P g^-1, and 79.24%, respectively.

Adsorption of lead (Ⅱ) from aqueous solution by modified Auricularia matrix waste: A fixed-bed column study

In this study, Auricularia Matrix Waste (AMW) was modified by sodium hydroxide and immobilized into granular adsorbent with sodium alginate to remove lead ions from aqueous solution through a fixed-bed column. The results of Scanning Electron Microscope-Energy Dispersive X-ray (SEM-EDX) and Fourier Transform Infrared Spectroscopy (FTIR) illuminated that immobilization greatly changed the structure, elements, polarity and functional groups of the adsorbent. Amino, hydroxyl, carboxyl groups on the adsorbent actively participated lead(II) adsorption and cation exchange also played an important role in adsorption process. The effects of bed length, flow rate and lead ions concentration determined the breakthrough characteristics and remarkably impacted lead(II) adsorption. The maximum adsorption capacity of lead(II) was 151.7 mg/g, when the influent bed, bed height and initial concentration were 15 mL/min, 25 mL/min and 150 mg/L, respectively. Thomas model was more suitable than the Bohart-Adams model to describe the performance of lead(II) adsorption onto IMAMW.

Fixed bed column evaluation of phosphate adsorption and recovery from aqueous solutions using recycled steel byproducts

Excessive phosphorus loading from anthropogenic sources is a major cause of eutrophication of natural waters. Phosphorus is also a non-renewable natural resource that cannot be substituted with other sources. The objective of this study was to determine the feasibility of using recycled steel byproducts to remove and recover phosphate from aqueous solutions. Laboratory fixed bed column experiments were conducted with recycled steel chips of different sizes to evaluate phosphate adsorption characteristics and phosphate recovery efficiencies using alkaline solutions. The results showed that phosphate adsorption onto steel chip filters was characterized by an initial fast breakthrough followed by a stable removal phase. The cumulative phosphate adsorption capacities of the steel chips were 8.43-10.4 mg P/g following 4800 empty bed volumes with a 3 min contact time and an initial concentration of 10 mg P/L. The phosphate adsorption onto steel chips was favored at low flow rates, low pH values, and low organic carbon concentrations. Sodium hydroxide solutions effectively desorbed phosphate from the steel chips. The total phosphate desorption percentages were 58.9%, 64.2%, and 83.4% after 120 empty bed volumes using 0.05 M, 0.10 M, and 0.20 M NaOH solutions, respectively. Steel chips also exhibited high phosphate adsorption and desorption capacities when treating agricultural subsurface drainage water, municipal wastewater, and stormwater runoff. Overall, the results of this study suggest that recycled steel byproducts are efficient and promising low-cost phosphate capturing materials for sustainable phosphorus management.

Ammonium removal from aqueous solutions by fixed-bed column using corncob-based modified biochar

This study investigated the potential of removing ammonium ([Formula: see text]) from aqueous solutions using corncob based on modified biochar (MBCC) in the fixed-bed column. Corncob biochar was soaked in a mixture of HNO₃ 6.0 M and NaOH 0.3 M to prepare active binding sites for ammonium removal. The effect of initial ammonium concentrations (10-40 mg/L), flow rates (1-9 mL/min) and MBCC fixed-bed heights (8-24 cm) on the breakthrough characteristics of the adsorption system were studied. The results showed that the highest adsorption capacity of fix-bed column, the breakthrough time and value of C_t/C_o were 12.83 mg/g, 480 min and 0.862 ± 0.025 at 10 mg/L of initial ammonium concentration, 8 cm of MBCC fixed-bed height and 3 mL/min of flow rate, respectively. The breakthrough curve model in this study also indicated that all Yoon-Nelson, Thomas and Adam-Bohart models well fit with the experimental data with a high R². The results also proved that MBCC can be used as a potential adsorbent for eliminating [Formula: see text] in the fixed-bed column. The saturated MBCC was also regenerated and reused consecutively for four cycles. The usage of mixture of NaOH and NaCl in recovering MBCC was better than NaCl only.

Utilizations of agricultural waste as adsorbent for the removal of contaminants: A review

In recent years, various industrial activities have caused serious pollution to the environment. Due to the low operating costs and high flexibility, adsorption is considered as one of the most effective technologies for pollutant management. Agricultural waste has loose and porous structures, and contains functional groups such as the carboxyl group and hydroxyl group, so it can be invoked as biological adsorption material. Agricultural waste gets the advantages of a wide range of sources, low cost, and renewable. It has a good prospect for the comprehensive utilization of resources when used for environmental pollution control. This article summarized the current research status of agricultural waste in adsorbing pollutants, which pointed out the influencing factors of adsorption, expounded the adsorption mechanism of biological adsorption and introduced the related parameters of adsorption, proposed the application of adsorbents in engineering including adsorption in liquid and gas phases, at the same time it gave the future development prospect of agricultural waste as adsorbent.

Adsorption of phosphorus by alkaline Tunisian soil in a fixed bed column

The present study evaluates the phosphorus (P) adsorption by alkaline soil in fixed bed column mode operation. The effects of flow rate, bed height, and initial P concentration on breakthrough curves were evaluated. Data confirmed that both the breakthrough and exhaustion time increased in parallel with the rise in bed height and the decline in flow rate and initial P concentration. The adsorption capacity was observed to increase with decreasing flow rate and bed height and increasing initial concentration. Moreover, continuous adsorption experiments were conducted using three salts (NaCl, KCl and CaCl₂) with the same concentration (0.01 M) to investigate the P adsorption behavior in saline conditions. The results showed that all three salts improve the P adsorption in the soil column. Consequently, the bed performance was significantly enhanced with salts addition. The maximum adsorption capacity of 13.47 mg g^-1 for P, 16.13 mg g^-1 for P-NaCl, 22.10 mg g^-1 for P-KCl, 30.05 mg g^-1 for P-CaCl₂ was attained at an initial influent concentration of 300 mg g^-1, bed height of 22 cm, and flow rate of 10 mL min^-1. TheCaCl₂ addition was therefore the most effective in increasing P adsorption. Thomas, Yoon-Nelson and Clark models were applied to experimental results to forecast the breakthrough curves by nonlinear regression analysis. Meanwhile, the bed depth service time model was employed to examine the effective model parameters in scaling up the process using linear regression analysis. The values of correlation coefficient (R²) and the sum of squared error evidenced that the Thomas model is the most appropriate model to fit the experimental data. The reusability experiment showed that the adsorbent material still had high P adsorption capacity, and tolerable desorption efficiency.

Water decontamination containing nitrate using biosorption with Moringa oleifera in dynamic mode

This study was conducted to assess the feasibility of using Moringa oleifera Lam. (MO) seeds in the biosorption of nitrate present in aqueous solutions by means of batch and fixed-bed column biosorption processes. The batch assays showed that nitrate biosorption is enhanced under experimental conditions of pH 3 and a biosorbent mass of 0.05 g. For the experiments in dynamic mode, the results obtained from the statistical parameters showed that lesser pH, lesser feed flow rate, and higher initial concentration will result in an increase of the maximum capacity of the bed. These conditions were confirmed by experimental analysis. The best experimental conditions, according to the values for percentage removal (91.09%) and maximum capacity (7.69 mg g^-1) of the bed, were those used in assay 1, which utilized pH 3, feed flow rate of 1 mL min^-1, and initial nitrate concentration of 100 mg L^-1.

Submerged membrane adsorption hybrid system using four adsorbents to remove nitrate from water

Nitrate contamination of ground and surface waters causes environmental pollution and human health problems in many parts of the world. This study tests the nitrate removal efficiencies of two ion exchange resins (Dowex 21K XLT and iron-modified Dowex 21K XLT (Dowex-Fe)) and two chemically modified bio-adsorbents (amine-grafted corn cob (AG corn cob) and amine-grafted coconut copra (AG coconut copra)) using a dynamic adsorption treatment system. A submerged membrane (microfiltration) adsorption hybrid system (SMAHS) was used for the continuous removal of nitrate with a minimal amount of adsorbents. The efficiency of membrane filtration flux and replacement rate of adsorbent were studied to determine suitable operating conditions to maintain the effluent nitrate concentration below the WHO drinking standard limit of 11.3 mg N/L. The volume of water treated and the amount of nitrate adsorbed per gramme of adsorbent for all four flux tested were in the order Dowex-Fe > Dowex > AG coconut copra > AG corn cob. The volumes of water treated (L/g adsorbent) were 0.91 and 1.85, and the amount of nitrate removed (mg N/g adsorbent) were 9.8 and 22.2 for AG corn cob and Dowex-Fe, respectively, at a flux of 15 L/(m²/h).

Development, modification, and application of low-cost and available biochar derived from corn straw for the removal of vanadium(v) from aqueous solution and real contaminated groundwater

In this work, a low-cost and available material for use as a permeable reactive barrier (PRB) to prevent vanadium in groundwater from leaking into river water was developed. Three modified biochars were prepared from available corn straw pretreated with CsCl, Zn(ii), and Zr(iv) to enhance ion exchange capacity (IEC) and specific surface area, and were designated as Cs-BC, Zn-BC, and Zr-BC, respectively. These materials were characterized via IEC, N₂ adsorption–desorption, Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analyses. The Langmuir isotherm model could be applied for the best fit for the adsorption data of Cs-BC and Zr-BC, indicating that vanadium(v) sorption occurred in a monolayer. The vanadium(v) adsorption capacities of Cs-BC, Zn-BC, and Zr-BC were 41.07, 28.46, and 23.84 mg g⁻¹, respectively, which were 3.22–5.55 times higher than that of commercial activated carbon (AC) (7.40 mg g⁻¹), probably because of their higher IECs and specific surface areas after modification. In addition, no heavy metal leaching was found from the modified biochars during the adsorption processes when pH > 2. According to the FTIR and XRD patterns, the adsorption mechanism of Cs-BC and Zr-BC was ion exchange, whereas for Zn-BC, it was mainly surface precipitation and electrostatic attraction. The adsorption of vanadium(v) onto the modified biochars was independent of pH in the range of 4.0 to 8.0. Furthermore, the removal efficiency of the vanadium(v) in real contaminated groundwater from the catchment of the Chaobei River by Zn-BC reached 100% at a dose of 4 g L⁻¹. Hence, modified biochars are promising PRB filling materials for removing vanadium(v) from contaminated groundwater.

In this work, a low-cost and available material for use as a permeable reactive barrier (PRB) to prevent vanadium in groundwater from leaking into river water was developed.

Removal of Tetrabromobisphenol A by adsorption on pinecone-derived activated charcoals: Synchrotron FTIR, kinetics and surface functionality analyses

This study explored the adsorption of Tetrabromobisphenol A (TBBPA) on pinecone-derived activated charcoal. The interactions between TBBPA and activated-charcoal surface, as well as the corresponding effects of functionality and adsorption capacities, were investigated through synchrotron FTIR, kinetics and surface functionality analyses. It was found that multiple acid functional groups and their interactive effects played important roles. The adsorption on activated charcoal from Yellow pinecone was favored by the surface with high polarity, low aromaticity, and low surface area. In comparison, adsorption on activated charcoal from Scot pinecone was favored by the surface with high aromaticity and high surface area. The adsorption capacity and removal efficiency were significantly dependent upon the contents of acid functional groups on charcoal surface. This study showed that the newly presented evidence of interactions between oxygen-containing functional groups and TBBPA will be helpful for exploring the treatment and transport of such a contaminant in the environment.

Adsorption of phosphate from aqueous solution using electrochemically modified biochar calcium-alginate beads: Batch and fixed-bed column performance

Batch and continuous fixed-bed column studies were investigated using electrochemically modified biochar calcium-alginate beads (EMB-CABs) as an adsorbent for the removal of phosphate from aqueous solutions. Batch experiments revealed that the phosphate adsorption behavior of EMB-CABs and its structural characteristics were highly dependent on pH condition. Also, kinetics and equilibrium isotherms studies demonstrated that the experimental data correlated well with the pseudo-second-order and Sips isotherm models, respectively. The effects of different operating parameters such as bed height, initial phosphate concentration, and flow rate were investigated in a continuous fixed-bed column, and the experimental data were fitted to three different breakthrough models, the Adams-Bohart, Thomas, and Yoon-Nelson models. The results suggested that the Yoon-Nelson model showed better agreement with the breakthrough curves than other models. Lastly, the design parameters for a large-scale column were calculated via the scale-up approach using the breakthrough parameters obtained from lab-scale column tests.

Predicting the propagation of concentration and saturation fronts in fixed-bed filters

The phenomenon of adsorption is widely exploited across a range of industries to remove contaminants from gases and liquids. Much recent research has focused on identifying low-cost adsorbents which have the potential to be used as alternatives to expensive industry standards like activated carbons. Evaluating these emerging adsorbents entails a considerable amount of labor intensive and costly testing and analysis. This study proposes a simple, low-cost method to rapidly assess the potential of novel media for potential use in large-scale adsorption filters. The filter media investigated in this study were low-cost adsorbents which have been found to be capable of removing dissolved phosphorus from solution, namely: i) aluminum drinking water treatment residual, and ii) crushed concrete. Data collected from multiple small-scale column tests was used to construct a model capable of describing and predicting the progression of adsorbent saturation and the associated effluent concentration breakthrough curves. This model was used to predict the performance of long-term, large-scale filter columns packed with the same media. The approach proved highly successful, and just 24-36 h of experimental data from the small-scale column experiments were found to provide sufficient information to predict the performance of the large-scale filters for up to three months.