Ammonia Adsorption Research Articles

Removal of ammonia nitrogen from wastewater using activated carbon prepared from waste tyres

Abstract In this work, the removal of ammonia nitrogen (NH4-N) on activated carbon prepared from waste tyres was conducted in batch studies as a function of adsorbent dosage, pH, temperature, contact time and initial concentration. The pore structure of activated carbon was characterized by N2 adsorption. The optimal conditions for the efficient adsorption of ammonia nitrogen onto waste tyre-activated carbon were found to be an adsorbent dosage of 0.4 g/L, pH 9.0, temperature of 20 °C, contact time of 90 min and initial ammonium nitrogen concentration of 50 mg/L. The kinetics studies showed that the pseudo-second-order model offered the best connection of the adsorption data. The Langmuir model was found to provide the best fit for the experimental data. The thermodynamic results showed that the adsorption of ammonia onto waste tyre-activated carbon was exothermic, random and spontaneous in nature.

Unexpected promotional effects of HCl over CeO2-based catalysts for NOx reduction against alkali poisoning

In the flue gas of stationary NOx emission source, HCl was deemed to be one of the poisons of NOx reduction catalysts since it can react with ammonia to form NH4Cl and adhere to oxide surface, reducing the redox property and blocking the active sites of catalysts for selective catalytic reduction of NOx with NH3 (NH3-SCR). Herein, unexpected promotional effects of HCl over CeO2-based catalysts for NOx reduction against alkali poisoning have been unraveled. The modification of gaseous HCl on the surface of CeO2 constructed Cl-Ce-O-Ce-OH and Cl-Ce-O-Ce3+ sites, providing additional Brønsted and Lewis acid sites to facilitate ammonia adsorption. It is worth noting that HCl can not only directly neutralize alkali metal to reduce alkalinity, but also increase the acidity to offset the encroachment of acid sites by alkali metal poisoning. The lower NO adsorption energy and weaker oxidation property of Cl-Ce-O-Ce3+ sites also prevented the accumulation of inert nitrate on the surface of alkali metal poisoned catalyst. This work unveils multi-promotion mechanisms for the enhanced catalytic activity and anti-alkali poisoning of gaseous HCl modified cerium-based NOx reduction catalysts, providing a new thinking based on pollutant interaction for further development of highly efficient NOx reduction catalysts in multipollutant flue gas.

Selective catalytic reduction of nitric oxide with a novel Mn–Ti–Ce oxide core-shell catalyst having improved low-temperature activity and water tolerance

A novel core-shell-shell Mn–Ti–Ce oxide catalyst (MnOx@TiO2@CeO2) was synthesized by a three-step method and applied for the selective catalytic reduction of NOx with ammonia (NH3-SCR). The catalyst exhibited an excellent low-temperature activity with NOx conversion >80% in a broad temperature range under both dry (120–260 °C) and wet (180–255 °C) conditions with a weight hourly space velocity (WHSV) of 240,000 mL/(g·h). Nitrogen physisorption and X-ray photoelectron spectroscopy (XPS) results showed that the formation of the inner TiO2 shell significantly increased the specific surface area, surface Mn4+/Mn ratio and chemisorbed oxygen, which could provide more active sites and promote the oxidation of NO to NO2. Ammonia temperature-programmed desorption (NH3-TPD) results indicated that the formation of the outer CeO2 shell not only extensively increased the surface acid sites but also enhanced the acid strength, beneficial for the ammonia adsorption and resulting in a good water tolerance.

The capacity of Polyurethane Sponge to Adsorb Nitrate, Ammonium, and Phosphate

Nitrate, ammonium, and phosphate are the main contaminants in agricultural runoff that can harm aquatic organisms if in high concentrations reaches water bodies, for that contamination must be controlled. Polyurethane sponge is a durable material and can be used for filtering those contaminants from wastewater, but studies on the mechanism of adsorption by this material are still rare. Therefore, the purpose of this study is to predict the adsorption capacity, removal efficiency, isotherm, and adsorption kinetics of polyurethane sponge on ammonium, nitrate, and phosphate removal. The results of the study show that polyurethane sponge can remove nitrate, ammonium, and phosphate by adsorption mechanism. The highest maximum adsorption capacity is nitrate in 5-hour mixing time, followed by ammonium in 2- hour mixing time, and the last one is phosphate in 3-hour mixing time. The isotherm that is suitable for presenting the removal of nitrate and ammonium is the Freundlich isotherm, while the Langmuir isotherm is more suitable for the removal of phosphate. The adsorption kinetics which fit to describe the mechanism of nitrate and ammonium adsorption is the intra-particle diffusion model, while the phosphate adsorption kinetics is more suitable to be described by the Pseudo first-order model.

Compositional characterization of nine agricultural waste biochars: The relations between alkaline metals and cation exchange capacity with ammonium adsorption capability

We converted different biochars from nine common feedstock were prepared for aqueous NH4+ adsorption. The biochars were classified into three groups: wood-like (B@A: wood chips, white popinac wood, pinecone), shell-like (B@B: rice husk, longan shell, water caltrop shell), and other agricultural wastes (B@C: corncob, sugarcane bagasse, and coconut fiber). We aimed to characterize the cation exchange capacity (CEC), alkaline metal composition, and other physicochemical properties of biochars and to examine their relation to NH4+ adsorption. Our as-prepared biochars were mesoporous with a large surface area of 142–371 m2/g and highly negatively charged surface (pHzpc of 0.91–1.64). The ash contents and contact angle characterization distinguished the three biochar groups into: hydrophilic, low-ash B@A; super hydrophilic, high-ash B@B; and hydrophobic, mid-ash B@C. Alkaline metals (K, Na, Ca, and Mg) were found up to 40 g/kg, while CEC varied from 27.80 to 292.63 meq/kg. At [NH4+]0 of 15 mM, NH4+ adsorption by biochars was mostly effective at pH∼7, following the order: B@B > B@C > B@A with sorption capacity qe of 0.04–0.15 mmol/g. The adsorption isotherms followed Langmuir model (R2 = 0.95–0.99), indicating the monolayer sorption process. From principle component analysis, we revealed that the ubiquitously-used physicochemical characterization, such as pHzpc, wettability, surface-pore characteristics, carbon and ash contents, presented minor roles in the NH4+-biochar adsorption, with statistically negative or insignificant correlations with qe. By contrast, CEC and alkaline metal contents strongly correlated to qe, with R2 > 0.9, p < 0.05, indicating the predominance of the cation exchange mechanism in this study.

Hybrid constructed wetlands amended with zeolite/biochar for enhanced landfill leachate treatment

Landfill leachate contains high concentrations of ammonia and recalcitrant organic compounds, which can interfere with wastewater treatment processes. Hybrid constructed wetlands (CWs), consisting of Vertical Flow (VF) CWs followed by Horizontal Flow (HF) CWs, are low cost technologies for onsite leachate treatment. This study investigated the potential of low-cost adsorbent materials, a natural zeolite mineral (clinoptilolite) and biochar, to enhance leachate treatment in hybrid CWs. Two mesocosm hybrid CWs were set up at a Florida (US) landfill. In the Adsorbent-CW 10% (v/v) of zeolite was added to the VF-CW to enhance nitrification and 13% (v/v) biochar was added to the HF-CW to increase microbial activity and plant growth. A Control-CW contained only gravel. Both systems were planted with cattails (Typha latifolia) and cordgrass (Spartina alterniflora) and operated at varying hydraulic loading rates for ~2 years. A HF-CW containing wood chips (Woodchip-CW) was added downstream of the Adsorbent-CW during the final 6-months of operation to enhance denitrification. Results showed that zeolite addition to the VF-CW significantly increased nitrification rates by 16–93% due to cycles of ammonium adsorption and bioregeneration under intermittent loading conditions. Biochar addition increased removal of organic matter (21–26% to 29–44%) and color (1–18% to 7–49%), and improved wetland plant growth and nitrogen removal due to enhanced plant growth and rhizosphere microbial activity. Addition of the Woodchip-CW reduced nitrate accumulation, resulting in total nitrogen removals of up to 79%.

Nutrient Recovery from Poultry Wastewater by Modified Biochar: An Optimization Study

In this work, we proposed and tested a method for utilizing agricultural waste and alum sludge as an effective adsorbent to treat poultry wastewater. The product was also targeted to be used as fertilizer for agriculture. Modified biochar was produced from crop residues, sludge from a water treatment plant, and magnesium salt. The produced biochar was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller analysis, and X-ray diffraction. The adsorption of ammonia and phosphate in both synthetic and actual poultry wastewater by the produced biochar was conducted. The effect of experimental conditions such as N to P ratio, initial concentrations of ammonium and phosphate, pH, and the amount of biochar on the adsorption capacity for ammonia and phosphate were also investigated. The results from the experiment showed that the best adsorption capacities were 60.64 mgNH4+-N/g and 66.24 mgPO43--P/g, which were produced at the optimum conditions of N to P ratio of 1.25, initial concentration of 90 mg/L, pH 6, and biochar mass of 0.105 g. These results create an opportunity for the effective production of slow-release fertilizer from crop residues and alum sludge for ecological agriculture in the future.

Metal ion/metal hydroxide loaded resin for ammonia removal from solutions containing high salinity by ligand exchange: Stability of metal ions during decomplexation of ammonia ligand

Ligand exchange of ammonia with ammine-complexing transition metals loaded on the substrate has received more attention for removing ammonia from solutions containing high salinity. However, the stability between transition metal and substrate was destroyed by the desorbent in the process of the ligand exchanger recycling and ammonia ligand decomplexation, leading to metal elution and reducing the adsorption competency of the ligand exchanger. Herein, metal(ion)-loaded resins (Me(ion)-LR) were prepared and the stability of metal ions during the three-round ammonia adsorption–desorption process was studied. The results showed the ammonia adsorption capacity of Cu2+-D751, Cu2+/Ni2+-D751 and Cu2+/Zn2+-D751 resin were 5.39, 5.80 and 5.65 mg/g, respectively and the shedding percent of Cu2+ is lower than that of Ni2+ and Zn2+. Aimed for the high ammonia selectivity and low metal ion dissolution, metal(ion)-loaded resins were modified with NaOH to obtain metal(hydroxides)-loaded resins (Me(hydroxides)-LR). The stability of metal ions during the three-round ammonia adsorption–desorption process was also investigated. Meanwhile, the mechanism of the Me(hydroxides)-LR for ammonia removal was explored. The results suggested that the Cu(OH)x-D751, Cu(OH)x/Ni(OH)x-D751 and Cu(OH)x/Zn(OH)x-D751 resin have higher ammonia adsorption capacity and reached 5.79, 8.25 and 7.94 mg/g, respectively. The shedding percent of Cu2+ and Zn2+ decreased obviously. Experimental and characterization results show that the ammonia removal by Me(hydroxides)-LR was primarily due to coordination complexation and electrostatic interaction.

Co3O4 hollow nanotubes for the catalytic oxidation of C2-chlorinated VOCs

Structured Co3O4 catalysts with a hollow nanotube morphology were prepared by several synthesis routes based on the Kirkendall effect. The resulting samples were kinetically evaluated in the gas-phase oxidation of vinyl chloride and 1,2-dichloroethane, two model C2-chlorinated volatile organic compounds; and exhaustively characterised by means of BET measurements, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, thermogravimetry and temperature-programmed techniques (adsorption of ammonia and chlorinated VOC, O2-TPD, H2-TPR and TPO). The performance of the prepared nanotubes was essentially controlled by the presence of active oxygen species at the surface, which in turn depended on the Co2+/Co3+ molar ratio, and the adsorption capacity of the catalyst for the chlorocarbon. Both pollutants were efficiently converted to deep oxidation products at relatively low temperatures. In addition, the optimal catalyst exhibited an appreciable stability when operating during 120 h.

Continuous adsorption of ammonium from primary and digester effluents using biosolids-derived biochar and cation exchange resin

Conventional biological treatment of wastewater can remove ammonium in the form of nitrogen gas, thus the opportunity of recovering the nutrient is lost. This study explored the continuous adsorption of ammonium from wastewater (primary and digester effluents) using biochar and cation exchange resin. The biochar was produced via the pyrolysis of biosolids (stabilised sewage sludge), and its ammonium adsorption performance was compared with a commercial cation exchange resin. Adsorption studies suggested that ammonium removal from synthetic wastewater was higher than from real effluents due to the competitive uptake of other components in the stream. Biochar with 100–500 μm particle size gave an ammonium adsorption capacity of 0.17 and 0.53 mg g−1 for primary and digester effluents, respectively. However, resin outperformed biochar with an estimated adsorption capacity of 17.96 and 28.38 mg g−1 for primary and digester effluents, respectively. Furthermore, the biochar bed was saturated in a few seconds, while the resin bed had a breakthrough time of 3 and 21 h, depending on the conditions applied. Therefore, it was proposed to treat the wastewater with biochar to obtain N-laden biochar and then send the resulting effluent to a series of resin columns for complete ammonium removal. The economic analysis of the process generated a net present value of $6 M and $0.6 M and a payback period of 6 and 10 years using primary and digester effluents, respectively. The profitability result is highly sensitive to the products sale price, the number of regeneration cycles of resin, and biosolids management cost.

Remarkable N2-selectivity enhancement of NH3-SCR over HPMo modified MnCo-BTC@SiO2 catalyst

In this work, the phosphomolybdate (HPMo) modification strategy was applied to improve the N2 selectivity of MnCo-BTC@SiO2 catalyst for the selective catalytic reduction of NOx, and further, the mechanism of HPMo modification on enhanced catalytic performance was explored. Among MnCo-BTC@SiO2-x catalysts with different HPMo concentrations, MnCo-BTC@SiO2-0.75 catalyst exhibited not only the highest NH3-SCR performance (∼95% at 200-300°C) but also the best N2 selectivity (exceed 80% at 100-300°C) due to the appropriate redox capacity, greater surface acidity. X-ray photoelectron spectrometer (XPS) and temperature programmed reduction of H2 (H2-TPR) results showed that the modification with HPMo reduced the oxidation-reduction performance of the catalyst due to electron transfer from Mo5+ to Mn4+/Mn3+ and prevent the excessive oxidation of ammonia adsorption species. NH3 temperature-programmed desorption of (NH3-TPD) results showed that the modification with HPMo could significantly improve the surface acidity and NH3 adsorption, which enhance the catalytic activity and N2 selectivity. In-situ diffused reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS) revealed that modification with HPMo increased significantly the amount of adsorbed NH3 species on the Bronsted acid site and CB/CL, it suppressed the production of N2O by inhibiting the production of NH species, the deep dehydrogenation of ammonia adsorption species. This study provided a simple design strategy for the catalyst to improve the low-temperature catalytic performance and N2 selectivity.

Efficient adsorption of ammonia on activated carbon from hydrochar of pomelo peel at room temperature: Role of chemical components in feedstock

Activated carbon derived from the organic solid waste is a promising material for ammonia removal. The components in the feedstock would affect the performance of activated carbon, but the detailed effect mechanism remains unknown. To reveal the correlations between the components of the feedstock and different ammonia adsorption styles of activated carbon, this study used pomelo peel to prepare ZnCl2-loaded activated carbon for ammonia adsorption via hydrothermal carbonization and KOH activation, focusing on the effect of the chemical components (cellulose, xylan, pectin, and lignin) on the physicochemical properties and adsorption performance of activated carbon. For raw activated carbon in moist conditions, ammonia was mainly adsorbed in the form of Lewis/Brønsted acid-base (37.8 mg/g), followed by the ZnCl2 coordination compound and organic amine forms (22.3 mg/g). Lignin-added activated carbon had the highest adsorption capacity, 91.2 mg/g in moist conditions, followed by cellulose-added and xylan-added activated carbon. The presence of lignin was beneficial for the formation of the phenolic group of activated carbon (increased by 111.3%), which promoted ammonia adsorption in the form of Lewis acid-base, especially in dry condition. Cellulose and xylan enhanced the formation of carboxylic (i.e., increased by 53.0% for cellulose) and lactonic groups (i.e., increased by 73.4% for cellulose) of activated carbon, leading to an increase of ammonia adsorption in the form of Brønsted acid-base and organic amines in moist conditions. The results illustrated the detailed effect of the chemical components in the feedstock on the ammonia adsorption styles, which could guide the selection of appropriate materials to prepare activated carbon for highly efficient ammonia adsorption under various situation.

Simultaneous ammonium and phosphate removal with Mg-loaded chitosan carbonized microsphere: Influencing factors and removal mechanism

A novel Mg-loaded chitosan carbonized microsphere (MCCM) was prepared for simultaneous adsorption of ammonium and phosphate in this study, through the investigation of preparation procedures, addition ratio, and preparation temperature. Pollutants removals by MCCM were more acceptable with 64.71% for ammonium and 99.26% for phosphorus, compared with chitosan carbonized microspheres (CCM), Mg-loaded chitosan hydrogel beads (MCH) and MgCl2·6H2O. Addition ratio of 0.6:1 (mchitosan: mMgCl2) and preparation temperature of 400 °C in MCCM preparation were responsible for pollutant removal and yield. The effect analysis of MCCM dosage, solution pH, pollutant concentration, adsorption mode and coexisting ions on the removal for both ammonium and phosphate indicated that pollutants removals were increased with increasing MCCM dosages, and achieved the peak at pH 8.5, but presented to be stable with Na+, K+, Ca2+, Cl−, NO3−, CO32− and SO42−, except for Fe3+.Adsorption mechanisms discussion implied that simultaneous ammonium and phosphate removal with MCCM was attributed to struvite precipitation, ion exchange, hydrogen bonding, electrostatic attraction and Mg–P complexation, suggesting that MCCM presents a new way for simultaneous concentrated ammonium and phosphate removal in wastewater treatment.

Ionic liquid hybrid metal–organic frameworks for efficient adsorption and selective separation of ammonia at high temperature

Efficient adsorption and selective separation of ammonia at high temperature is a crucial and challenging issue. In this work, a series of stable ionic liquid hybrid materials have been developed by simple impregnation of ionic liquids into stable metal–organic framework Al-fum with 1D pores. The hybrid material [C2N][Zn3Cl7]@Al-fum-60% exhibited an exceptionally high uptake (9.9 mmol/g at 80 °C, 8.8 mmol/g at 100 °C) at high temperature, excellent uptake (9.8 mmol/g at 25.0 °C) at low ammonia concentration (100,000 ppm), and remarkable selective separation performance (selectivity factor is 25.1) of NH3 from NH3/CO2 mixture at high temperature. The NH3 uptake of [C2N][Zn3Cl7]@Al-fum-60% at 100 °C was higher than the capacity of most of typical porous NH3 adsorbents at room temperature. It is revealed that such superior NH3 capacity and selective separation performance are mainly attributed to coordination interactions of NH3 to Zn centre of the ionic liquids and the hydrogen bonding interactions of NH3 with Cl of the ionic liquids and NH3 with μ-OH of Al-fum.

Adsorption Studies of Ammonia, Protein, and Phytic Acid Using Chitosan Fiber Coated with Oxidized Cellulose Nanofiber

Herein, chitosan (CS) fibers coated with TEMPO-oxidized cellulose nanofibers (CS/TOCN fibers) were successfully prepared using a wet spinning technique; CS was dissolved in acetic acid to obtain a CS doping solution. The tensile strength and ammonia adsorption percentages increased with increasing TOCN concentration. The maximum ammonia adsorption percentage (41.39%, 8.3 mg/g) was obtained when 2% NaOH and 0.01% TOCN were used as the coagulation solution. Additionally, the adsorption of model proteins, including lysozyme (Lz), cytochrome C (Cyt C), and bovine serum albumin (BSA), were studied. In water, the CS/TOCN fibers with negative charges adsorbed more Lz with positive charges than CS fibers containing positive charges. Contrastingly, CS fibers adsorbed more Cyt C and BSA containing negative charges in phosphate-buffered saline solutions than CS/TOCN fibers. Furthermore, the adsorption percentage of phytic acid using the CS/TOCN fibers reached 64.18% (288 mg/g) within 60 min. Thus, TOCNs improved the tensile properties of CS fibers and preferred positively charged materials contaminated in water, such as ammonia, Lz, and phytic acid.

The transformation of amorphous aluminum oxide during the catalytic dehydration of aromatic alcohol

A wide application of aluminum oxides in the synthesis of heterogeneous catalysts for petrochemistry and oil refining makes it necessary to reveal factors determining the efficiency of the catalytic systems. However, the literature provides no data concerning the effect produced by the amorphous phase in aluminum oxide catalysts on characteristics of the catalytic reaction. Usually the content of amorphous phase is not categorized; however, its presence may significantly deteriorate the catalyst efficiency. X-ray diffraction analysis, low-temperature nitrogen adsorption, electron microscopy and temperature-programmed desorption of ammonia were used in this work to examine samples of the amorphous aluminum oxide obtained from two different precursors. Catalytic properties of the samples were investigated during the vaporphase dehydration of 1-phenylethanol to styrene. It was shown for the first time that the transformation of amorphous aluminum oxide in the catalytic reaction decreased the conversion of alcohol from 84 (for the fresh catalyst) to 64 % (for the regenerated sample). Crystallization of amorphous aluminum oxide by the high-temperature treatment enhanced the catalytic performance, but it did not reach the desired values due to a considerable deterioration of the textural characteristics and acidic properties of the aluminum oxide surface.

Adsorption and quantitative fluorescence-based measurement of ammonium ions using a chitosan-based hydrogel combined with p-hydroxybenzoic acid

Ammonium removal in high-density fish cultures is highly reliant on time-consuming and costly biological treatment methods. Therefore, the development of cheap and rapid chemical methods has recently garnered increasing attention. Our study developed a dissolved ammonium removal method using a chitosan-based hydrogel (Cht-HG) modified with 0.3 mM of p-hydroxybenzoic acid (Cht-0.3PHBA-HG). Our proposed method enabled the adsorption and measurement of dissolved ammonium via fluorescence detection. In the ammonium adsorption test, the maximum adsorption capacities (qm) of Cht-HG and Cht-0.3PHBA-HG were 11.6 mg g−1 and 19.9 mg g−1, respectively. Cht-0.3PHBA-HG exhibited a relatively elevated adsorption capacity (i.e., 1.71-fold higher adsorption efficiency) due to the morphological and chemical modifications attributed to p-hydroxybenzoic acid (PHBA). These findings were confirmed by our chemical characterization and adsorption test results. Particularly, the adsorbed ammonium atomic percentages (at.%) of Cht-HG-NH4 and Cht-0.3PHBA-HG-NH4 were 6.33 % and 15.2 %, respectively. Compared to Cht-HG, the adsorption properties of Cht-0.3PHBA-HG were more stable in a pH range of 2–8. Moreover, we quantitatively analyzed the oxidation of the combined PHBA at different dissolved ammonium concentrations (0.1–5.0 mM) using fluorescence detection. The fluorescence sensitivity of ammonium was maintained, even in high concentrations of common electrolytes (Ca2+, K+, Mg2+, Na+, and PO43-). The ammonium adsorption mechanisms of Cht-0.3PHBA-HG were strongly consistent with the pseudo-first order (PFO), pseudo-second order (PSO), and Langmuir models. In addition to its role as an adsorbent, Cht-0.3PHBA-HG could also be used to detect ammonium in real time.

Efficient capture and storage of ammonia in robust aluminium-based metal-organic frameworks

The development of stable sorbent materials to deliver reversible adsorption of ammonia (NH3) is a challenging task. Here, we report the efficient capture and storage of NH3 in a series of robust microporous aluminium-based metal-organic framework materials, namely MIL-160, CAU-10-H, Al-fum, and MIL-53(Al). In particular, MIL-160 shows high uptakes of NH3 of 4.8 and 12.8 mmol g−1 at both low and high pressure (0.001 and 1.0 bar, respectively) at 298 K. The combination of in situ neutron powder diffraction, synchrotron infrared micro-spectroscopy and solid-state nuclear magnetic resonance spectroscopy reveals the preferred adsorption domains of NH3 molecules in MIL-160, with H/D site-exchange between the host and guest and an unusual distortion of the local structure of [AlO6] moieties being observed. Dynamic breakthrough experiments confirm the excellent ability of MIL-160 to capture of NH3 with a dynamic uptake of 4.2 mmol g−1 at 1000 ppm. The combination of high porosity, pore aperture size and multiple binding sites promotes the significant binding affinity and capacity for NH3, which makes it a promising candidate for practical applications.

Zeolites for Nitrogen Recovery from the Anaerobic Membrane Bioreactor Permeate: Zeolite Characterization

Anaerobic Membrane Bioreactor technology has great advantages for treating wastewater, including energy recovery from organic matter. However, when the legislation requires that effluent standards be met in sensitive areas, this treatment cannot remove the nutrients, thus the permeate generated needs post-treatment. Apart from the biological processes, ion exchange is an alternative treatment for this stream since it can remove nutrients and concentrate them for later recovery as fertilizers. In this work, the feasibility of using a natural zeolite (clinoptilolite) for treating NH4 from AnMBR permeate was studied and tests were carried out on the adsorption kinetics of ammonium. Isotherm tests verified that activating natural zeolite to its -Na form improves its performance by 20% and increases qe from 2.37 to 2.86 mg NH4-N/g for a Co of 30 mg NH4-N/L. It was also found that the cations present in the water (especially Ca2+ and Na+) caused a 22% reduction in ammonium adsorption while organic matter was responsible for improving the retained ammonium by 22%. It was also found that the working pH (7.2 ± 0.2) is close to the optimal pH range (6–7) for zeolite performance. The tests on the AnMBR permeate indicate that clinoptilolite is a suitable material since treating this stream can retain up to 7.44 mg NH4-N/g.

Ammonia capture by adsorption on doped and undoped activated carbon: Isotherm and breakthrough curve measurements

Doped and undoped activated carbons were characterized by scanning electron microscopy, energy dispersive spectrometry, helium pycnometry, mercury intrusion porosimetry, and adsorption isotherms of nitrogen and carbon dioxide. The adsorption isotherms of ammonia were measured at 278, 293, 303, and 318 K and pressures up to 105 kPa using a manometric system on both activated carbons. These measurements showed that the doped activated carbon had the highest ammonia adsorption capacity, especially at low ammonia partial pressures. The Toth isotherm model was used to correlate the adsorption isotherms and estimate the isosteric heats of adsorption at 278 K and at zero fractional loading that were 25.6 and 41.9 kJ.mol−1 for undoped and doped activated carbon, respectively. Ammonia breakthrough curves were measured with both activated carbons in a pilot column. The behavior of doped and undoped activated carbon during adsorption/desorption cycles shows that despite the possibility of regeneration and enhancement of undoped activated carbon, the doped activated carbon provides better single use performance. A study of the operating parameters of doped activated carbon was conducted to evaluate the effects of ammonia concentration, gas flow rate, operating temperature, and relative humidity. The occurrence of two independent ammonia adsorption mechanisms (chemical and physical) on the doped activated was demonstrated.