Adsorption Of NH4 Research Articles

Modeling and Optimizing of NH4+ Removal from Stormwater by Coal-Based Granular Activated Carbon Using RSM and ANN Coupled with GA

As a key parameter in the adsorption process, removal rate is not available under most operating conditions due to the time and cost of experimental testing. To address this issue, evaluation of the efficiency of NH4+ removal from stormwater by coal-based granular activated carbon (CB-GAC), a novel approach, the response surface methodology (RSM), back-propagation artificial neural network (BP-ANN) coupled with genetic algorithm (GA), has been applied in this research. The sorption process was modeled based on Box-Behnben design (BBD) RSM method for independent variables: Contact time, initial concentration, temperature, and pH; suggesting a quadratic polynomial model with p-value < 0.001, R2 = 0.9762. The BP-ANN with a structure of 4-8-1 gave the best performance. Compared with the BBD-RSM model, the BP-ANN model indicated better prediction of the response with R2 = 0.9959. The weights derived from BP-ANN was further analyzed by Garson equation, and the results showed that the order of the variables’ effectiveness is as follow: Contact time (31.23%) > pH (24.68%) > temperature (22.93%) > initial concentration (21.16%). The process parameters were optimized via RSM optimization tools and GA. The results of validation experiments showed that the optimization results of GA-ANN are more accurate than BBD-RSM, with contact time = 899.41 min, initial concentration = 17.35 mg/L, temperature = 15 °C, pH = 6.98, NH4+ removal rate = 63.74%, and relative error = 0.87%. Furthermore, the CB-GAC has been characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET). The isotherm and kinetic studies of the adsorption process illustrated that adsorption of NH4+ onto CB-GAC corresponded Langmuir isotherm and pseudo-second-order kinetic models. The calculated maximum adsorption capacity was 0.2821 mg/g.

Corn cobs efficiently reduced ammonia volatilization and improved nutrient value of stored dairy effluents

Dairy farms produce considerable quantities of nutrient-rich effluent, which is generally stored before use as a soil amendment. Unfortunately, a portion of the dairy effluent N can be lost through volatilization during open pond storage to the atmosphere. Adding of covering materials to effluent during storage could increase contact with NH4+ and modify effluent pH, thereby reducing NH3 volatilization and retaining the effluent N as fertilizer for crop application. Here the mitigation effect of cover materials on ammonia (NH3) volatilization from open stored effluents was measured. A pilot-scale study was conducted using effluent collected at the Youran Dairy Farm Company Limited, Luhe County, Jiangsu, China, from 15 June to 15 August 2019. The study included seven treatments: control without amendment (Control), 30-mm × 25-mm corn cob pieces (CC), light expanded clay aggregate - LECA (CP), lactic acid (LA) and lactic acid plus CC (CCL), CP (CPL) or 20-mm plastic balls (PBL). The NH3 emission from the Control treatment was 120.1 g N m−2, which was increased by 38.1% in the CP treatment, possibly due to increased effluent pH. The application of CC reduced NH3 loss by 69.2%, compared with the Control, possibly due to high physical resistance, adsorption of NH4+ and effluent pH reduction. The lactic acid amendment alone and in combination with other materials also reduced NH3 volatilization by 27.4% and 31.0–46.7%, respectively. After 62 days of storage, effluent N conserved in the CC and CCL treatments were 21.0% and 22.0% higher than that in the Control (P < 0.05). Our results suggest that application of corn cob pieces, alone or in combination with lactic acid, as effluent cover could effectively mitigate NH3 volatilization and retain N, thereby enhancing the fertilizer value of the stored dairy effluent and co-applied as a soil amendment after two months open storage.

Simultaneous recovery of ammonium and total phosphorus from toilet tail water by modified palygorskite-bentonite clay.

Suitable treatment of toilet sewage is a worldwide challenge. The anaerobic baffled reactor (ABR)-microbial fuel cell (MFC)-microbial electrolysis cell (MEC) (AMM) coupling treatment system has been constructed achieving effective removal of carbon, nitrogen, and phosphorus from toilet sewage and resource recovery; however, ammonium (NH4 + -N) and total phosphorus (TP) accumulation in tail water is a found problem of the system. In this study, acid-modified and alkali-heat modified palygorskite-bentonite (Pal-Ben) were used to recover NH4 + -N and TP from the AMM toilet tail water simultaneously. The higher adsorption capacity of the modified clay is attributed to the changes of surface structure of the material. The modified clay Pal-Ben (mass ratio 1:3) activated with alkali performed the highest NH4 + -N and TP recovery rates of 83.6% and 85.5%, respectively. The adsorption of NH4 + -N was more in line with the pseudo-second-order kinetic model and confirmed to be a chemical adsorption process, while the adsorption of TP was more in line with the pseudo-first-order kinetics and a physical adsorption process; the adsorption capacity of NH4 + -N accelerated with decrease of TP removal when pH increased. This study developed a low cost and high capacity of alkaline thermally modified clay removing/recovering NH4 + -N and TP from toilet tail water simultaneously. PRACTITIONER POINTS: A cheap composite clay was developed to recover nitrogen and phosphorus from toilet tail water simultaneously. The low costs and high capacity of alkaline thermally modified clay make it stand out in NH4 + -N and TP removal of toilet tail water. The process mechanism of simultaneous nitrogen and phosphorus recovery was clarified with characterization and kinetic model fitting. The used clay loaded with nutrients could be applied as a slow-release compound fertilizer for soil improvement.

Synthesis of adsorbent materials from FELDSPAR for removal of ammonium in water

In this study, adsorbent materials from natural feldspar were fabricated for application in +NH4 removal. Raw, pretreated by HCl 3M, and modified feldspar by NaOH and aluminum (Al powder, Al(OH)3, and AlCl3.6H2O) were used. Feldspar was modified under different experimental conditions including without calcination and calcinated at 500ºC and 700ºC. The influence of various operating parameters consisting of material size, adsorption time, +NH4 initial concentration and material dosage were investigated. Adsorbent materials &lt; 0.1 mm in size showed the highest adsorption efficiency. Subsequently materials with size of &lt; 0.1 mm were used for the following studies to investigate the affect of other parameters on +NH4 adsorption process. The highest removal efficiency (31.10%) and removal capacity (21.80 mg/g) were obtained by modified feldspar by NaOH and AlCl3.6H2O with calcination at 700ºC at +NH4 initial concentration of 5 ppm. Results from the scanning electron microscope (SEM) showed the differences on surfaces of adsorption materials. Modified feldspar had a clean surface and more tiny pores compared to those of raw and pretreated feldspar resulting in an increased surface area. Consequently +NH4 adsorbent efficiency and removal capacity were increased. By BET (Brunauer, Emmett and Teller) the specific surface areas of adsorbent materials were analyzed and the surface areas of raw, pretreated and modified feldspar were 0.484 m2/g, 0.988 m2/g and 2.024 m2/g, respectively. +NH4 adsorbent mechanisms of all raw, pretreated, and modified feldspar materials were found to follow the Langmuir adsorption isotherm with the correlation coefficient R2 = 0.989 which described the monolayer type of the adsorption.

In vitro and in vivo Evaluation of Succinic Acid-Substituted Mesoporous Silica for Ammonia Adsorption: Potential Application in the Management of Hepatic Encephalopathy.

PurposeHepatic encephalopathy (HE) is a critical situation in which liver failure affects brain function. HE could result in a state of coma and death. The liver is the main organ for ammonium ion (NH4+) metabolism. Hence, acute and/or chronic liver failure could lead to hyperammonemia. NH4+ is the most suspected neurotoxic agent in HE. Thus, finding new therapeutic options to decrease plasma and brain NH4+ levels has a significant clinical value. Mesoporous silica (MS) particles have revolutionized many aspects of pharmaceutical sciences, including drug delivery systems. Moreover, recently, MS has been applied as agents for the detoxification of chemicals (eg, drugs and poisons).MethodsFirst, MS particles containing amine groups (MS-NH2) were synthesized in co-condensation processes. Then, the structure was modified by succinic anhydride to have MS-SA. The MS-SA was characterized (FT-IR, XRD, X-ray photoelectron spectroscopy (XPS), DLS-Zeta FESEM-EDX, and HRTEM). Then, the potential of MS-NH2 and MS-SA particles in adsorption of NH4+ was investigated in vitro and in vivo. MS-NH2 and MS-SA were incubated with increasing concentrations (0.1–10 mM) of NH4+, and the scavenging capacity of the investigated particles was evaluated. On the other hand, different doses (1 and 5 mg/kg per day) of nanoparticles were administered to a hyperammonemia animal model.ResultsIt was figured out that both MS-NH2 and MS-SA significantly scavenged NH4+ in the in vitro model. However, the NH4+ scavenging capability of MS-SA was more significant. Administration of MS-NH2 and MS-SA also considerably decreased the level of ammonium in plasma and brain and improved cognitive and locomotor activity in hyperammonemic animals. The effects of MS-SA were more significant than MS-NH2 in the HE animal model.ConclusionCollectively, our data suggest that MS particles, especially succinic acid-functionalized MS, could act as special ancillary treatment in HE as a critical clinical complication.

Interpretation of Isotherm Models for Adsorption of Ammonium onto Granular Activated Carbon

High amounts of ammonium (NH4+) discharged in receiving water can lead to eutrophication. The adsorption of NH4+ from synthetic solution onto granular activated carbon (GAC) was scrutinized with respect to initial solute concentration (10 mg L−1), solution volume (0.2 L), adsorbent dosage (4 – 20 g), and contact time. Experimental data can be well described by the pseudo-second-order kinetic model (R2 &gt; 0.994) and Freundlich isotherm model (R2 = 0.936), suggesting that chemisorption and multilayer adsorption occurred. Furthermore, this study explored the feasibility of using the Freundlich isotherm model to estimate the removal efficiency or required amount of adsorbent. The result findings indicated that GAC has a good potential to adsorb NH4+ from water and thus giving new insights into environmental engineering practices.

The biodiversity - N cycle relationship: a 15N tracer experiment with soil from plant mixtures of varying diversity to model N pool sizes and transformation rates

We conducted a 15N tracer experiment in laboratory microcosms with field-fresh soil samples from a biodiversity experiment to evaluate the relationship between grassland biodiversity and N cycling. To embrace the complexity of the N cycle, we determined N exchange between five soil N pools (labile and recalcitrant organic N, dissolved NH4+ and NO3− in soil solution, and exchangeable NH4+) and eight N transformations (gross N mineralization from labile and recalcitrant organic N, NH4+ immobilization into labile and recalcitrant organic N, autotrophic nitrification, heterotrophic nitrification, NO3− immobilization, adsorption of NH4+) expected in aerobic soils with the help of the N-cycle model Ntrace. We used grassland soil of the Jena Experiment, which includes plant mixtures with 1 to 60 species and 1 to 4 functional groups (legumes, grasses, tall herbs, small herbs). The 19 soil samples of one block of the Jena Experiment were labeled with either 15NH4+ or 15NO3- or both. In the presence of legumes, gross N mineralization and autotrophic nitrification increased significantly because of higher soil N concentrations in legume-containing plots and high microbial activity. Similarly, the presence of grasses significantly increased the soil NH4+ pool, gross N mineralization, and NH4+ immobilization, likely because of enhanced microbial biomass and activity by providing large amounts of rhizodeposits through their dense root systems. In our experiment, previously reported plant species richness effects on the N cycle, observed in a larger-scale field experiment within the Jena Experiment, were not seen. However, specific plant functional groups had a significant positive impact on the N cycling in the incubated soil samples.

Biochar produced from the co-pyrolysis of sewage sludge and walnut shell for ammonium and phosphate adsorption from water

Pyrolysis of sewage sludge to obtain biochar is an environmentally friendly method of sewage sludge utilization. In this study, sewage sludge and walnut shell were co-pyrolyzed to produce biochar, which was utilized in the adsorption of ammonium and phosphate from water. Brunauer–Emmett–Teller analysis, X-ray diffraction spectroscopy, scanning electron microscopy, and Fourier transform infrared techniques were applied to analyze the physical and chemical properties of the biochar. The sewage sludge-based biochar consisted of rich metal oxides and functional groups, and the addition of walnut shell was beneficial for the development of porous structure. When the mixing ratio of sewage sludge and walnut shell was 3:1, the derived biochar (MBC3-1) showed a high adsorption capacity for NH4+ in neutral or weak alkaline water. Pure sewage sludge biochar (SBC) was the best option for the adsorption of PO43− in a wide pH range of water. The adsorption of NH4+ and v on MBC3-1 and SBC were controlled by intraparticle diffusion and pseudo-second-order kinetic models, respectively. Isothermal studies indicated that multiple adsorption processes occurred in the adsorption of NH4+ and PO43−, and the maximum adsorption capacity of NH4+ and PO43− reached 22.85 mg/g and 303.49 mg/g on MBC3-1 and SBC, respectively. Thermodynamic analysis confirmed the exothermic and endothermic nature for NH4+ and PO43− adsorption on biochar, respectively.

NH4+-K+ co-loaded clinoptilolite as a binary fertilizer

ABSTRACTUnderstanding the potential of clinoptilolite (CLI) for adsorption of NH4+ and K+, providing appropriate fertilizer formula, and evaluation of the produced zeolitic nutrient sources (ZNSs) to meet the plant need are the main objectives of this study. Three ZNSs (NH4+-saturated, K+-saturated and dual-purpose NH4+-K+ saturated CLI) were produced, assessed, and compared with commercial N and K fertilizers (CFs) on corn growth in a greenhouse. The results indicated that CLI can potentially adsorb both NH4+ and K+ to the maximum values of 25.00 mg-NH4+ g−1 and 47.61 mg-K g−1, respectively, and chemisorptions mainly followed the process of adsorption. Saturation of zeolite by NH4+ and K+ occurred after 10 and 15 d which lead to ZNSs with 2% and 5% of N and K, respectively. NH4+-K+ saturated CLI contained 1% N and 1% K. The greenhouse experiment showed no significant difference between ZNSs and CFs on plant growth. However, the application of both N and K in the form of zeolitic sources significantly increased the uptake of N by the plant. The highest uptake of K (2.05 g pot−1) occurred in plants supplied with both natural zeolite and CFs. The present results may benefit the future utilization of ZNSs in environmental friendly farming practices.

Rapid recovery of nitrogen retention capacity in a subtropical acidic soil following afforestation

Understanding soil nitrogen (N) dynamic and availability during afforestation (the conversion of cropland to forest plantations) is critical to maintain forest growth and long-term productivity, especially in rainfall-rich, subtropical region. However, only few studies have investigated the inherent N transformation processes involved in N availability in subtropical acidic soils. In a 15N tracing study, nine soils from croplands, 10-y and 50-y afforested woodlands were sampled to investigate the changes in soil gross N transformation rates in humid subtropical China. Gross N transformation rates were not significantly different in soils under 10- and 50-y after afforestation. Compared to cropland, however, afforestation stimulated the rates of mineralization, microbial NH4+ immobilization and adsorption of NH4+, leading to a faster turnover of NH4+ pool in afforested soils. Moreover, afforestation inhibited autotrophic nitrification and resulted in NO3− production dominated by heterotrophic nitrification. Furthermore, afforestation significantly enhanced NO3− consumption mainly through the increase in microbial NO3− immobilization rather than dissimilatory NO3− reduction to NH4+ in soil. These differences in gross N transformation rates resulted in low net NO3− production and strong NO3− retention capacity in afforested soils, similar to that found in undisturbed natural forest. Our results suggest a rapid recovery (several years) of soil N retention following afforestation. Soil NO3− retention capacity was correlated positively with TOC, TN, WHC, CEC, Al, free Al oxide and exchangeable Al3+, but negatively with pH, Ca and exchangeable Ca2+, indicating that the absence of agricultural management (e.g., N fertilizer and liming) and alteration in soil environment by tree establishment are responsible for the recovery of N retention capacity in subtropical acidic soils during afforestation.

Microwave-Assisted Synthesis of a Novel Biochar-Based Slow-Release Nitrogen Fertilizer with Enhanced Water-Retention Capacity

Biochar-based slow-release nitrogen fertilizers (BSRFs) have been arousing a great deal of interest from researchers and academics, but many of these fertilizers do not possess water-retention capacity. In this work, a polymer matrix has been introduced into NH4+-loaded biochar (N-BC), using microwave (MW) irradiation, for the purpose of acting as a superabsorbent polymer to improve soil water-retention capacity. The polymer matrix is composed of cotton stalks (CSs), acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and bentonite (bent.). N-BC was prepared via the adsorption of NH4+ onto BC, and its adsorption behavior was investigated. The structure and properties of the resulting samples were characterized using various characterization methods. Results suggest that BSRFs could significantly improve the water-holding and water-retention capacity of soil. BSRFs effectively reduced the nitrogen-release rate (69.8% of nitrogen was released after 30 days), and possessed low nitrogen-leaching-loss amounts (10.3%), low nitrogen migrate-to-surface-loss amounts (7.4%), and high nitrogen-use efficiency (64.27%), as compared to NH4Cl and N-BC, consequently effectively promoting cotton plant growth. The soil burial degradation test of BSRFs indicated that BSRFs possessed good degradability. BSRFs may therefore have promising applications in modern, sustainable agriculture, while MW irradiation is an important strategy with which to produce BSRFs.

Environmental-friendly montmorillonite-biochar composites: Facile production and tunable adsorption-release of ammonium and phosphate

The cleaner production of environmentally friendly materials for the controlled adsorption and desorption of ammonium and phosphate in wastewater treatment and soil fertility maintenance is a challenge. Here we show that a class of clay mineral-biochar composites which were produced via a facile cleaner pyrolysis process starting from two abundant natural materials (montmorillonite and bamboo powder). The montmorillonite-biochar composites (MBC) were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, N2 adsorption/desorption isotherms, thermogravimetric analysis, and scanning electron microscopy. The adsorption and slow-release characteristics of MBC samples for NH4+ and PO43− in aqueous solution were evaluated. Montmorillonite (Mt) acted as a solid acidic catalyst and catalyzed the pyrolysis of bamboo powder to biochar and lower the pyrolysis temperatures. Both biochar and Mt contributed to the texture and structure, which provided varied surface and various adsorptive sites. The Langmuir maximum adsorption capacity of MBC samples for NH4+ and PO43− was 12.52 mg·g−1 and 105.28 mg·g−1. The adsorption of NH4+ onto the MBC sample was primarily controlled by surface adsorption and partially by a CEC process. The adsorption capacity of PO43− resulted from the electrostatic attraction or ionic bonding between PO43− and cations in the MBC samples such as Ca2+, Mg2+, Al3+ and Fe3+. The release of NH4+ and PO43− from the NH4+- and PO43−-laden MBC samples was merely 0.30–4.92% and 2.63–5.09% within 2–88 h. These findings implied that the MBC samples prepared from low-cost Mt and bamboo can remove NH4+ and PO43− from aqueous solution by adsorption and the resultant NH4+- and PO43−-laden MBC samples can be used as an effective slow-release fertilizer of N and P.

Synthesis of pure NaA zeolites from coal fly ashes for ammonium removal from aqueous solutions

The pure NaA zeolites used as adsorbents for ammonium removal were successfully synthesized from coal fly ash by means of alkaline fusion followed by hydrothermal treatment. The experiment samples were characterized in terms of X-ray diffraction, X-ray fluorescence, Scanning electron microscopy, Fourier transform infrared spectroscopy, and Automated specific surface area and pore size analyzer. The results showed that the NaOH solution’s concentration, reaction temperature, and reaction time had significant effects on the species of the zeolite phases. Well-ordered cubic NaA zeolite with Brunauer–Emmett–Teller specific surface areas of 41.6 m2/g was prepared in 3 M NaOH solution at 353 K for 3 h. The adsorption behavior of NH4 + from aqueous solution onto NaA zeolites was investigated at different initial concentrations, pH values, and contact times. The adsorbent equilibrium could be reached within 60 min, and the maximum removal efficiency of NH4 + was achieved at pH 7.0. The Langmuir and Freundlich adsorption models were also applied to describe the equilibrium isotherms. The obtained results show that the experimental data have a better (R 2 = 0.99) fit to Freundlich model and the adsorption of NH4 + ions using synthesized NaA zeolite is favorable.

Calcium-Ammonium Selectivity of Two Benchmark Soils from Botswana as Assessed by Competing Semi-empirical Ion Exchange Equations

The effectiveness of lime-ammonium-nitrate (LAN) as a nitrogen (N) fertilizer in weathered soils depends on the respective selectivity for ammonium (NH4) and calcium (Ca) by the soils. The study assessed Ca2+/NH4+ exchange selectivity of two benchmark soils from Botswana and examined the soil fertility management implications. Surface horizons (0–20 cm) of Pellustert and Haplustalf were equilibrated with 50 ml stock solution containing variable concentrations of Ca2+ and NH4+. The Ca2+/NH4+ exchange data were fitted into the Vanselow (KV), Gaines and Thomas (KGT), Davies (KD), and the regular solution (KRS) equations. The selectivity coefficients for the Ca2+/NH4+ exchange reactions varied widely with the soil exchanger composition except for the relatively stable KRS. The selectivity coefficients indicated strong preference for NH4+ to Ca2+. The thermodynamic exchange constant, Kex, was 5.75 ± 1.24 in the Pellustert, indicating preferential adsorption of NH4+, but not in the Haplustalf with Kex = 0.92 ± 0.27. The free energy for Ca2+/NH4+ exchange (ΔG°ex) was negative (−4.26 ± 0.59 kJ mol−1) in the Pellustert but slightly positive in the Haplustalf (0.34 ± 0.87 kJ mol−1). In conclusion, the soil-NH4 complex was more stable than soil-Ca complex in the Pellustert, indicating LAN as a N fertilizer would have greater potential effectiveness in the Pellustert than in the Haplustalf.

Surfactant-free fabrication of SiO2-coated negatively charged polymer beads and monodisperse hollow SiO2 particles

Abstract SiO2 coating on the surface of negatively charged polymer beads (n-PBs) succeeded in a typical Stober process with tetraethyl orthosilicate (TEOS). The core–shell structure of the resulting particles was confirmed by TEM observation and EDS mapping. Hollow SiO2 particles (HSPs) with monodisperse size and high dispersibility were further fabricated by calcining the obtained SiO2-coated n-PBs in air at 600 °C. Two advantages of using n-PBs for the fabrication of SiO2-coated polymer beads and HSPs were revealed as (1) lower cost with respect to positively charged polymer beads (p-PBs) and (2) improving the dispersibility of the obtained HSPs. According to our observations, there are two prerequisites for the formation of SiO2 shells on n-PBs, as (1) the high surface charge density of n-PBs and (2) low water concentration in reaction system. A mechanism was proposed for explaining the coating of SiO2 on the like-charged polymer beads. In that mechanism, the adsorption of NH4+ ions on the surface of n-PBs played a critical role for SiO2 coating, as it not only screened the surface charge of n-PBs to reduce the energetic barrier for SiO2 deposition, but also caused the accumulation of OH− ions to restrict the location where SiO2 nucleated to the surface of n-PBs.

Biochar produced from oak sawdust by Lanthanum (La)-involved pyrolysis for adsorption of ammonium (NH4+), nitrate (NO3−), and phosphate (PO43−)

A series of biochars were prepared by pyrolyzing oak sawdust with/without LaCl3 involvement at temperature of 300–600°C, and approximate and ultimate analyses were carried out to check their basic characteristics. Meanwhile, the releases of readily soluble NH4+, NO3− and PO43− from biochars and the adsorption of NH4+, NO3− and PO43− by biochars were investigated. Results indicated that the involvement of LaCl3 in pyrolysis could advance the temperature of maximum mass loss by 10°C compared with oak sawdust (CK), and potentially promoted biochar yield. Overall, the releases of readily soluble NH4+, NO3− and PO43− from biochars were negatively related to pyrolysis temperature, and the releases were greatly weakened by La-biochars. Additionally, the adsorption to NH4+ can be promoted by the biochars produced at low temperature. On the contrary, the NO3− adsorption can be improved by increasing pyrolysis temperature. The highest PO43− adsorption was achieved by the biochars produced at 500°C. According to the results of adsorption isotherms, the maximum adsorption capacity of NH4+, NO3− and PO43− can be significantly promoted by 1.9, 11.2, and 4.5 folds using La-biochars. Based on the observations of FT-IR, SEM–EDS, and surface functional groups, the improvement of NH4+ adsorption was potentially associated with the existing acidic function groups (phenolic-OH and carboxyl CO). The increased basic functional groups on La-biochars were beneficial to improve NO3− and PO43− adsorption. Besides, PO43− adsorption was also potentially related to the formed La2O3.

Investigation of ammonium ion removal from aqueous solutions using arene- and propylsulfonic Acid functionalized mesoporous silica adsorbents.

To counter environmental threats to the water resources polluted by NH, which is common in wastewaters and agricultural runoff, adsorption using mesoporous functional materials represents a promising alternative to existing treatment methods. In this study, adsorption of NH ions from aqueous solutions was investigated on arene- and propylsulfonic acid functionalized SBA-15 mesoporous silica materials. The adsorbents were synthesized via co-condensation and post-synthesis grafting procedures. Adsorbents were characterized by means of X-ray diffraction, N physisorption, titration, and elemental analyses. The effects of pH, NH initial concentration, temperature, adsorbent loading, organosilane molar ratio, and presence of competitive species on the performance of the adsorbent materials were examined. All the adsorbents having an organosilane/silica molar ratio of 1:5 displayed maximum adsorption capacity around approximately 25 mg g NH at the lowest temperature investigated, 5°C. This capacity decreased with increasing temperature. For a given initial NH concentration, the removal efficiency () increased with increasing adsorbent loading. For instance, increased from 24 to 59% when the adsorbent loading was increased from 2 to 10 g L at 25°C. The adsorption isotherms were well described by a Langmuir model equation. Adsorption capacity improved with increasing organosilane/silica molar ratio, reaching 42 mg g NH with a ratio of 2:5 at 25°C. Arene- and propylsulfonic acid functionalized SBA-15 materials synthesized via co-condensation and post-synthesis grafting proved to be effective high-capacity adsorbents for the removal of NH ions from aqueous solutions.

Robust biological nitrogen removal by creating multiple tides in a single bed tidal flow constructed wetland

Achieving effective total nitrogen (TN) removal is one of the major challenges faced by constructed wetlands (CWs). To address this issue, multiple “tides” were proposed in a single stage tidal flow constructed wetland (TFCW). With this adoption, exceptional TN removal (85% on average) was achieved under a high nitrogen loading rate (NLR) of around 28gNm−2day−1, which makes the proposed system an adequate option to provide advanced wastewater treatment for peri-urban communities and rural area. It was revealed that the multiple “tides” not only promoted TN removal performance, but also brought more flexibility to TFCWs. Adsorption of NH4+–N onto the wetland medium (during contact period) and regeneration of the adsorption capacity via nitrification (during bed resting) were validated as the key processes for NH4+–N conversion in TFCWs. Moreover, simultaneous nitrification denitrification (SND) was found to be significant during the bed resting period. These findings will provide a new foundation for the design and modeling of nitrogen conversion and oxygen transfer in TFCWs.

The Synthesis of Titanium Dioxide (TiO2) Powder for Cold Spray Process

Titanium dioxide (TiO2) has attracted numerous attentions due to its high photocatalytic property. TiO2 as photocatalyst is best to be coated over large area substrate (walls, windows, etc.). In this case, cold spray process is the most suitable technique, not only because its simplicity and efficiency for large area deposition, but also because it is a low temperature process that would retain the high photocatalytic anatase phase of TiO2 in the coating. However, cold spraying of hard ceramic materials, such as TiO2, is widely known to be difficult. In this study, we are reporting a novel synthesis method of TiO2 powder for cold spray via the hydrolysis of titanyl sulphate (TiOSO4) with addition of ammonium sulphate ((NH4)2SO4). It is a relatively simple synthesis method that can obtain pure anatase structure even without high temperature treatment, although post treatments, such as hydrothermal and calcination further increase the crystallinity and change the morphology of synthesised TiO2. It is believed that the synergetic effect of post treatments and adsorption of NH4+ and SO42− ions on the surface of TiO2 causes the alteration in morphology of TiO2 powder. Finally, the cold spray spot test shows that the TiO2 powders can be cold sprayed. This is a remarkable finding as the difficulty of cold spraying TiO2 is widely known.

Pedotransfer Functions for Estimating Ammonium Adsorption in Soils

Urine depositions by grazing animals induce high concentration of ammonium (NH4+) in soils. The adsorption of NH4+ in the soil plays an important role in the fate of the urine deposited N. However, adsorption isotherms for a wide range of soils are not readily available. Pedotransfer functions (PTFs) that relate easily measurable and widely available soil properties to the NH4 adsorption capacity of soils might be a useful tool to help predict the fate of the urine if they are sufficiently accurate. To derive PTF's for NH4 adsorption by soils, batch experiments were performed with eight different soils from New Zealand. The adsorption data for the different soils were fitted with the Freundlich isotherm and the model parameters related to soil properties including total C content, clay and sand fractions, and cation‐exchange capacity (CEC). Clay fraction and CEC were found to be most related to the Freundlich model parameters, and were used to derive PTFs. The PTFs were validated using NH4+ sorption data from the literature spanning a range of soils with different textures and CEC. Agreement between literature NH4 adsorption data and those calculated using the PTFs were good, with R2 of 0.7, provided that only soils with similar clay contents and CECs as those used for their development. While this is a potential limitation of the derived PTFs, the range of clay and CEC used are relevant for a wide range of soils.