Nitrate Adsorption Research Articles

Efficient nitrate adsorbent applicable to wide pH range derived from polyacrylonitrile (PAN) fiber

A thermally stabilized polyacrylonitrile (PAN) fiber was activated with sodium carbonate (Na2CO3) at 800 °C (PYR-8SC1) followed by annealing at 950 °C (PYR-8SC1-9.5HT30) to remove negatively charged surface oxygen and supplied for adsorption of nitrate in aqueous solution from acidic to weak basic range. Nitrogen adsorption-desorption analysis was conducted to examine the textural properties of PYR-8SC1-9.5HT30 sample comparing with the non-annealing sample of PYR-8SC1. Elemental analysis was performed to know the content of nitrogen and oxygen in the samples and X-ray photoelectron spectroscopy (XPS) was also applied to determine the amount of quaternary nitrogen (N-Q) species favorable for the nitrate adsorption. PYR-8SC1-9.5HT30 exhibited a stable high adsorption capacity in a wide equilibrium solution pH (pHe) range, particularly around neutral pHe, whereas PYR-8SC1 worked well only in acidic condition at pHe close to 3 or lower. Maintaining high adsorption capacities of nitrate on PYR-8SC1-9.5HT30 could be caused by not only surface exposure of positively charged graphitic N-Q species, but also the presence of positively charged oxygen and the absence of negatively charged pyridine N-oxide (N-X) and the other negatively charged nitrogen and oxygen species that might hinder the nitrate adsorption onto the surface of PAN activated carbon fiber (ACF).

Modified Grape Seeds: A Promising Alternative for Nitrate Removal from Water.

The aim of this work was to investigate grape seeds as a potential adsorbent for nitrate removal from water. Grape seeds were modified by quaternization and the applicability of the modified grape seeds (MGS) was evaluated in batch adsorption experiments. Fixed bed adsorption and regeneration studies were carried out to determine the regeneration capacity of MGS. The maximum adsorption capacity of 25.626 mg g−1 at native pH (6.3) for nitrate removal by MSG was comparable to that of the commercial anion exchange resin Relite A490 under similar conditions. The percent removal of nitrate from model nitrate solution was 86.47% and 93.25% for MGS, and Relite A490, respectively, and in synthetic wastewater 57.54% and 78.37%. Analysis of the batch adsorption data using isotherm models revealed that the Freundlich model provided a better fit to the data obtained than the Langmuir model, indicating multilayer adsorption. In kinetic terms, the results showed that the adsorption followed the pseudo-first order model. By investigating the adsorption mechanism, the results suggest that the intraparticle diffusion model was not the only process controlling the adsorption of nitrate on MGS. In column experiments (adsorption/desorption studies), three adsorption cycles were tested with minimal decrease in adsorption capacities, implying that this alternative adsorbent can be successfully regenerated and reused.

Computational prediction and experimental evaluation of nitrate reduction to ammonia on rhodium

We predicted the reaction energetics for nitrate reduction on rhodium surfaces in alkaline media using the density functional theory (DFT) in combination of implicit continuum solvation model. The study covered three typical facets including (111), (110) and (100) of Rh crystal, as well as the surface adsorption of five major chemical species (i.e., NO2−, NO, N2O, N2 and NH3) involved in nitrate reduction. Our calculation results reveal that Rh (110) exhibits activity for nitrate reduction towards ammonia with the widest potential range below 0.06 V, and Rh (100) has the best activity and selectivity towards ammonia above −0.57 V with the highest onset potential up to 0.15 V, the lowest activation energy at the rate-determining step from *N to *NH and the preferable configuration of nitrate adsorption at low surface coverage to suppress nitrogen formation. The optimal potential range for nitrate reduction towards ammonia on Rh (100) was predicted to be from 0.15 V to 0.09 V, which was further verified by our experimental evaluation of ammonia yield on commercial Rh/C electrocatalysts. The peak of ammonia yield rate of 34.4 μg·h−1·cm−2 as well as the faradic efficiency of 20.8% on the experimental sample exactly lie in the as-predicted potential range of Rh (100), hence consistently matching our computational predictions. Our study not only provides a detailed mechanistic understanding of nitrate reduction with quantified experimental detection of ammonia yield on rhodium, but also demonstrates reliable predictions via DFT in combined with implicit continuum solvation model for electrocatalysts.

Removal of nitrate from radioactive wastewater using magnetic multi-walled carbon nanotubes

In the solidification process using asphalt as a medium, nitrate oxidizes the medium and makes it unstable. Therefore, in order to efficiently remove nitrate from wastewater, a magnetic adsorbent was synthesized (m-MWCNTs), and physicochemical properties of m-MWCNTs were confirmed by SEM, TEM, XRD, FT-IR, BET, and VSM analyses. In the process of synthesizing m-MWCNTs, the amount of magnetite introduced on the surface of MWCNTs could be controlled by increasing the concentration of the chemical agent that becomes the Fe precursor. In addition, the amount of nitrate adsorption increased with higher magnetite content on the surface of MWCNTs. The adsorption process followed the Langmuir model and pseudo-second-order kinetics. In nitrate adsorption using m-MWCNTs, pH was the main condition to determine the adsorption amount, and as the pH increased, the amount of nitrate adsorption decreased. Thermodynamic experiments revealed that the adsorption of nitrate by m-MWCNTs is an endothermic and spontaneous process.

Recycling rice husk for removal of phosphate and nitrate from synthetic and swine wastewater: Adsorption study and nutrient analysis of modified rice husk

The objective of this study was to determine the adsorbent potential of rice husk and its modified form for phosphate and nitrate removal from synthetic and swine-farm wastewater. The mechanism of adsorption as well as the potential of phosphate-/nitrate- adsorbed rice husk as nutrient rich residue was also investigated. Two-step modification of RH (using base-washing (BW) and chemical modification (CM) was conducted to compare the phosphate and nitrate removal. The effects of several factors (pH, sorbent dosage, contact time, initial concentration, and coexistence of both ions) were investigated to gain insight into the adsorption rate, behavior, and mechanism of the modified RH regarding phosphate and nitrate removal. The results of Fourier-transform infrared spectroscopy showed that the modification was successful by crosslinking with the amine group of the chemical agent. Fitting the adsorption kinetic data of phosphate showed physical adsorption, intraparticle diffusion, and chemisorption, whereas for nitrate, the data indicated mainly chemisorption. Fitting the adsorption isotherm data of phosphate and nitrate together showed adsorption on a monolayer coating of anions on the homogeneous sorbent’s surface. The maximum phosphate and nitrate adsorption capacities were 6.94 and 2.46 mg/g, respectively, for a single adsorbate and 11.14 and 1.76 mg/g, respectively, for the binary solution. In real swine wastewater, removal efficiencies of phosphate, nitrite, nitrate, sulfate, and ammonia were 83.8%, 65.0%, >45.0%, 36.6%, and 2.6%, respectively, indicating that the modified RH would be effective for phosphate and nitrate removal from real wastewater. Finally, nutrient analysis of the phosphate- and nitrate-sorbed RH showed increases in nitrogen and phosphorus, which would be beneficial for further use of the RH as nutrient or fertilizer after adsorption.

Development and tailoring of amino-functionalized activated carbon based Cucumerupsi manni Naudin seed shells for the removal of nitrate ions from aqueous solution

The removal of nitrate ions with ethylenediamine (EDA)-functionalized activated carbon (AC-NH2) was studied in this work. Activated carbon prepared from Cucumerupsi manni Naudin seed shells using ZnCl2 (ACZ) was functionalized with EDA via a nitric acid oxidation followed by acyl chlorination and amidation process. The effect of pH, contact time, initial concentration and co-existing ions on the adsorption of nitrate ions have been investigated. The FTIR and elemental analysis revealed that amino groups were successfully grafted onto the ACZ after functionalization. The surface area and average pore of ACZ were found to be 1008.99 m2/g and 2.02 nm respectively. However, it was noticed that, after functionalization (AC-NH2), its surface area decreases to 113.43 m2/g meanwhile, its pore diameter increases to 2.48 nm. The experimental results of adsorption showed that AC-NH2 exhibit excellent nitrate ions uptake performance compared to ACZ which is attributed to the presence of the grafted amino groups on the ACZ. Nitrate adsorption follows pseudo-first-order kinetic model while the equilibrium adsorption data was best fitted the Freundlich isotherm suggesting that the adsorption process was predominated by physisorption. This study demonstrates that the prepared AC-NH2 is a promising adsorbent for nitrate ions removal from aqueous media.

Fabrication of lanthanum linked trimesic acid as porous metal organic frameworks for effective nitrate and phosphate adsorption

The potable water crisis worldwide may lead to the detoxification of aquatic pollutants which becomes the research hotspot. The construction of metal-organic frameworks (MOFs) serves as the promising adsorbent material for the efficient removal of toxic ions from aqueous solution. Hence, the present research article covers the development of lanthanum linked trimesic acid (LTA) based MOFs for soluble nitrate (NO3−) and phosphate (PO43−) adsorption from water. The developed LTA MOFs were characterized by numerous instrumentation techniques like FTIR, SEM, EDAX, XRD, TGA, DTA and BET studies. The function of LTA MOFs declares the enhanced removal properties on NO3−/PO43− adsorption at batch condition. The adsorption mechanism of LTA MOFs was explored along with kinetics, isotherms and thermodynamic studies. The emerging trends of LTA MOFs for controlling the water quality parameters were also discussed at field level. The synthesized LTA MOFs could be reused many cycles for adsorption technique.

Biochar-supported polyaniline hybrid for aqueous chromium and nitrate adsorption

Biochar adsorbents can remove environmental pollutants and the remediation of Cr(VI) and nitrate are considered. Cr(VI) is a proven carcinogen causing serious health issues in humans and nitrate induced eutrophication causes negative effect on aquatic systems around the world. Douglas fir biochar (DFBC), synthesized by fast pyrolysis during syn gas production, was treated with aniline. Then, a polyaniline biochar (PANIBC) composite containing 47 wt% PANI was prepared by precipitating PANI on DFBC surfaces by oxidative chemical polymerization of aniline in 2M HCl. PANIBC exhibited a point of zero charge (PZC) of 3.0 and 8.2 m2/g BET (N2) surface area. This modified biochar was characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM) morphology and surface elements, and oxidation states by X-ray photoelectron spectroscopy (XPS). PANIBC exhibited positive surface charge below pH 3, making it an outstanding adsorbent, for Cr(VI) removal. Cr(VI) and nitrate removal mechanisms are presented based on XPS analysis. DFBC and PANIBC Cr(VI) and nitrate adsorption data were fitted to Langmuir and Freundlich isotherm models with maximum Langmuir adsorption capacities of 150 mg/g and 72 mg/g, respectively. Cr(VI) and nitrate removal at pH 2 and 6 were evaluated by reducing the amount of PANI (9 wt%) dispersed on to DFBC. Adsorption capacities verses temperature studies revealed that both Cr(VI) and nitrate adsorption are endothermic and thermodynamically favored. Regeneration studies were conducted on both DFBC and PANIBC using 0.1M NaOH and PANIBC exhibited excellent sorption capacities for Cr(VI) and nitrate in lake water samples and in the presence of competitive ions.

Kinetic and Isotherm Studies of Nitrate Adsorption in Salt Water Using Modified Zeolite

Nitrate is the main form of nitrogen species in natural waters. Excessive nitrate concentration in water is highly undesirable, so that removal of the excessive nitrates in waters is very important. However, the challenge is purposed to remove the excessive nitrates in sea waters by considering anions-rich sea water. Adsorption is a favorable method for the nitrate removal process. Therefore, this research was aimed to study the kinetics and isotherm of nitrates adsorption in salt water. The adsorbent preparation was done by modifying natural zeolite with iron oxide. The adsorbent characterization was carried out by FT-IR spectroscopy and Gas Sorption Analyis methods. The results showed that the modified zeolite have Fe−O group vibrations as indicated by a peak at a wave number of 1404.18 cm−1 and an increased specific surface area. The modified zeolite is capable of adsorbing nitrate ions. The adsorption isotherms studies indicated that the modified zeolite is appropriate to the Dubinin-Radushkevich model. The average adsorption energy value (ED), obtained based on the Dubinin-Radushkevich isotherm <2 kJ/mole, showed that the nitrate adsorption on zeolite surface occurred physically. The most suitable adsorption kinetics model is the pseudo second order with the rate constant of 1.80´10−2 g/mg.min. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Adsorption of nitrate and nitrite from aqueous solution by magnetic Mg/Fe hydrotalcite

Abstract In this study, magnetic Mg/Fe hydrotalcite calcined material (M-CHT) was synthesized through the co-precipitation and calcination method, and was used to effectively remove nitrate and nitrite from water. M-CHT can restore its original layered structure after the adsorption of nitrate or nitrite, and can be easily separated by an applied magnetic field. The first-order and pseudo-second-order kinetic models (R2 ≥ 0.97) can better describe the adsorption kinetic process. The equilibrium isotherm showed that the Langmuir model provided a better fit to the experimental data than the Freundlich model for nitrates and nitrites. With temperature increased from 298 to 308 K, the maximum adsorption capacity obtained by the Langmuir model increased from 10.60 to 16.90 mg-N/g for nitrate and 7.89 to 14.28 mg-N/g for nitrite, respectively. The adverse effect of coexisting anions ranked in the order of ClO4− > Cl− > SO42− > F− > CO32− > PO43−. The actual Fe2+/Fe3+ value of M-CHT (0.56) is nearly consistent with the theoretical value of 0.5, and the saturation magnetic strength value of M-CHT is 9.15 emu/g, greatly contributing to the solid–liquid separation. Overall, M-CHT with features of magnetic properties and satisfactory adsorption capacity exhibits great promise for application in wastewater purification.

Covalently-bonded quaternized activated carbon for selective removal of NO3– in capacitive deionization

Nitrate pollution has become an increasingly serious water pollution problem worldwide. Capacitive deionization (CDI) technology is an emerging water treatment technology that can efficiently remove nitrate in water with advantages of simple process, high water recovery rate, low cost and energy consumption. In this work, we engineer a covalently bonded quaternized activated carbon (QRAC) material by silanization and investigate its selective adsorption of nitrate in mixed solution with extended voltage capacitive deionization (eV-CDI) mode. The results show that (1) the QRAC electrodes achieve selective adsorption due to the different adsorption binding energies of the quaternary ammonium group with Cl- and NO3–. The selectivity coefficient of QRAC-5 to NO3– reaches 2.7 at 0.4 V and the electrosorption capacity is 140% higher than that of AC in 5/5 mM KCl/KNO3 solution. (2) The electrosorption of QRAC electrodes are dominated by two aspects: physical adsorption by external electric field which occurs in the incipient stage and ion exchange adsorption by quaternary ammonium groups occurring in the following stage. (3) CDI experiments in simulated municipal wastewater show that SO42- had a negative effect on the adsorption capacity of NO3–, but QRAC electrode can still achieve separation effect in Cl-/NO3– solution system. These results show that covalently bonded quaternized activated carbon can achieve the effective separation and removal of NO3– in polluted water, and our work provides new insights into the selective electrosorption of CDI technology.

Optimization of Nitrate and Nitrite Anions Adsorption on Modified Silica using Batch Method

Ammonia inorganic compounds are compounds that are often found because it is soluble in ground water which causes health hazards that are carcinogenic, mutagenic, tetratogenic and cause metamoglobinemia. Ammonia compounds that have negative effects on humans are nitrate and nitrite anions. Disposal of liquid waste and the use of fertilizers cause nitrates and nitrites to dissolve so that it has a negative impact on groundwater. One of the efforts to overcome nitrate and nitrite in waste is by adsorping with adsorbent., where the adsorbent used is DMA modified silica. Characterization by adsorption of nitrites and nitrates from aqueous solution at various pH, concentrartions, and contact times. The result showed that silica modification with DMA increased the adsorption capacity of nitrates and nitrtites. The Langmuir isotherm yields a regression coefficient R2 = for 0.9809 for nitrate and 0.9469 for nitrite. Nitrate adsorption capacity of 0.1669 mg g-1 with an initial nitrate concentration of 60 ppm at pH 8 with stirring for 120 minutes while the maximum adsorption capacity of nitrite was 0.1669 mg g-1 with an initial nitrite concentration of 40 ppm at pH 6 with stirring for 120 minutes.

Enhanced adsorption and reduction performance of nitrate by Fe–Pd–Fe3O4 embedded multi-walled carbon nanotubes

Multi walled carbon nanotubes (MWCNTs) have attracted more and more attention as adsorbents due to their excellent adsorption properties. By loading metal particles on MWCNTs, the chemical reduction ability of adsorbed pollutants could be provided, so as to achieve the purpose of adsorption and degradation of pollutants. Therefore, the removal process of NO3−-N by Fe–Pd–Fe3O4/MWCNTs was studied, including rapid adsorption of initial pollutants, gradual reduction of intermediate products and re-adsorption of final products. The results showed that Fe–Pd–Fe3O4/MWCNTs completely removed NO3−-N within 2 h, 39% and 25% of which were converted into NO2−-N and NH4+-N. The adsorption efficiency, kinetics, capacity and adsorption energy all followed the order of NH4+-N > NO2−-N > NO3−-N. With the recoverability and reusability of Fe–Pd–Fe3O4/MWCNTs having been confirmed in 5 consecutive cycles, the removal rate of NO3−-N still reached 43%. It has been shown that MWCNTs prolonged the reducing power for NO3−-N, due to avoiding the aggregation of metal particles. The rapid adsorption of initial pollutants, effective stepwise reduction and convenient recovery processes were of great value for the rehabilitation of polluted water.

Study on adsorption of nitrate ion from biogas effluent by melaleuca biochar

Contamination of water resources by nitrate has become an important problem in recent decades. Although nitrate is not toxic, it can be converted into nitrite and cause serious harm to human health. One of the most effective methods of nitrate removal is the use of adsorbents. The objective of this study was to evaluate the nitrate adsorption efficiency from biogas solution by using melaleuca biochar that was pyrolysed at 700oC. Physical and chemical characteristics of melaleuca biochar were determined using a variety of methods including scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) test. Nitrate concentration was measured using a UV spectrophotometer with a wavelength of 660 nm. The results showed that the optimum conditions for the effective adsorption of nitrate ion onto melaleuca biochar were found to be pH 4, biochar dosage of 1 g L-1, and retention time of 15 min. The experimental data were fitted to different adsorption isotherms models (Langmuir, Freundlich models). The maximum nitrate adsorption capacity of melaleuca biochar was 15.5 mg g−1.

Adsorption of Nitrate and Ammonium from Water Simultaneously Using Composite Adsorbents Constructed with Functionalized Biochar and Modified Zeolite

The functionalized biochar was assembled on modified zeolite to synthesize a novel modified composite adsorbent. The latter was applied to simultaneous adsorption of ammonium and nitrate. The Box–Behnken design (BBD) in response surface methodology (RSM) was applied to optimize the parameters, which included ratio of raw materials, adsorbent dose, pH, and temperature. The chemical functional groups were determined by Fourier transform infrared adsorption (FT-IR). Stronger absorption peaks of amine groups indicated that the functionalized adsorbent could enhance the adsorption of contaminants. The composite adsorbent effectively increased NH4+ and NO3− adsorption capacity by porous structure recombination, change of surface morphology and further exposure of surface functional groups. The kinetic results indicate that the adsorption of both NH4+ and NO3− follows a pseudo-second-order nonlinear model. The Langmuir isotherm model fitted well the experimental data with a maximum adsorption capacity of 24.45 mg/g for nitrate and 24.63 mg/g for ammonium at 25°C. Nitrate was absorbed by electrostatic interactions with grafted amine groups and, in contrast, the ammonium adsorption was mainly related to ion exchange with Na+. The adsorption process of both nitrate and ammonium were spontaneous and exothermic. The adsorbents can be regenerated effectively in NaCl and NaOH mixed solutions, and the desorbed adsorbents are of high reusability and can be applied effectively at least for five cycles. Therefore, it has a great potential for nitrate and ammonium simultaneous removal from water environment.

Nitrate Adsorption capacity of Activated Gamalama Volcanic Ash

<p>The adsorption process of nitrate from an aqueous solution by using activated Gamalama volcanic ash was investigated. Gamalama volcanic ash (VA) was activated with HNO3 2M. The effect of adsorbent mass and initial nitrate concentration on nitrate adsorption were observed in this study. The adsorption process was conducted using a various mass of adsorbent (1 g, 2 g, 4 g, 6 g, and 8 g), various initial concentrations of nitrate (20 mg/L, 30 mg/L,40 mg/L, 50 mg/L, and 60 mg/L). The increasing of adsorbent mass decreased the adsorption capacity was observed. It was also found that the increase in initial concentration increased the adsorption capacity. The highest nitrate adsorption capacity showed by 1 gram adsorbent for 0.167 mg/g, and at nitrate initial concentration 80 mg/L, for 1.831 mg/g. Adsorption isotherm of nitrate on activated VA was determined and figured. These isotherms were modelled according to Freundlich and Langmuir adsorption isotherm.</p>

Synthesis and surface-functionalizing of ordered mesoporous carbon CMK-3 for removal of nitrate from aqueous solution as an effective adsorbent

In this study, the adsorption of nitrate onto ordered mesoporous carbon CMK-3 was investigated. First, CMK-3 was synthesized and then directly amino-functionalized by 3-aminopropyl trimethoxysilane (APTMS). The physicochemical properties of as-prepared adsorbent were characterized by XRD, EDS-SEM, FT-IR and N2 adsorption-desorption. Ultraviolet/visible spectroscopy was used to evaluate the adsorbent ability for nitrate reduction. In batch experiments, the influence of effective parameters such as contact time, adsorbent dosage, solution pH, initial concentration and temperature was investigated on the nitrate adsorption capacity. The obtained results indicated 100% removal efficiency for initial nitrate concentration of 50 mg l−1 and 78% for the concentration of 100 mg l−1, at low adsorbent dosage (3 g l−1) and very fast equilibrium attainment (5 min) without pH dependency (in the range of 2.0–8.0). The maximum nitrate adsorption capacity of Amino-CMK-3 was 48.78 mg g−1 in the concentration range of 50–250 mg g−1. Kinetic studies confirmed that the process followed a pseudo-second-order and that the Langmuir isotherm best fitted the equilibrium adsorption of nitrate. Nitrate desorption occurred after a reasonable time (3 h) and confirmed the adsorbent reusability without further treatment. The higher adsorption capacity of CMK-3 stemmed from its incredible mesoporous structure, including nano-channels that were completely functionalized by amino groups. Grafting aminopropyl groups potentially turned the CMK-3 to a promising adsorbent for nitrate removal.

Investigation of the removal and recovery of nitrate by an amine-enriched composite under different fixed-bed column conditions

Continuous adsorption of nitrate in a fixed-bed column can be an effective method for its removal from water. In this study, an amine-rich polymer composite adsorbent was prepared by crosslinking chitosan (CS) and polyethyleneimine (PEI) with glutaraldehyde (GLA). The CS-PEI-GLA was packed into columns and the effect of flow rate, influent concentration, bed height, and other ionic species on the column performance was investigated. The highest adsorption capacity was achieved at the lowest flow rate and highest influent concentration and bed height. Maximum adsorption capacity of 137.62 mg NO3−-N/g was determined from the Thomas model. The column had acceptable nitrate removal in the presence of 1000 ppm chloride but poor performance in the presence of 1000 ppm sulfate due to the competitive effect of sulfate for binding sites. The best recovery agent was 0.5 M NaCl as it could regenerate the column to <90 % of its capacity after 10 adsorption-desorption cycles. The adsorbent effectively removed nitrate as well as phosphate and total organic carbon from a real water sample. This study suggests that amine rich polymers can be good candidates for the removal of nitrate in contaminated water.

Nitrate removal from aqueous solution by way of adsorption on modified sheep wool

Acid modification of sheep wool changed the surface charge from a negative to a positive one as demonstrated by means of zero-charge point determination. The positive surface facilitated the adsorption of nitrate (NO3 −) anions. The amount of nitrates in solution within 20–100 mg/dm3 was determined applying a home-developed ultraviolet spectrometry method. A little more effective modifier was 0.01 M hydrochloric acid (HCl) than the 0.1 M one. In the case of citric acid concentration, the effect was opposite. Wool modified with hydrochloric acid showed higher nitrate adsorption (up to 5 mg/g) compared with the sample modified with citric acid, (up to 1.7 mg/g of nitrate and 3, respectively). Testing eight adsorption isotherm models indicated inhomogeneity of the adsorbed layer from chemical as well as physical aspects. The Freundlich, Temkin and Halsey models fitted best. The study demonstrated that biopolymer modified using a suitable acid has the potential to remove nitrates from an aquatic environment.

Comparative study of anion removal using adsorbents prepared from a homoionic clay

The adsorption capacity of adsorbent materials (organophilic clays) prepared from a homoionic clay was compared for the removal of nitrates and nitrites present in aqueous solution in batch systems at room temperature.The organophilic clays were obtained by replacing the exchange cations present in the precursor clays with quaternary ammonium cations. For this purpose, two precursor clays were used, a natural clay (FS) and the same clay exchanged with sodium (CP) and two ammonium cations with different structure: hexadecyltrimethylammonium (HDTMA) and benzyltriethylammonium (BTEA) with amounts equivalent to 1.5, 2.5 and 4.0 cation exchange capacity (C.E.C.). Ion exchange is important to obtain a good affinity between organoclay and anionic contaminants. The clays were characterized by XRD, FTIR and SEM-EDX. The maximum adsorption capacities of the CP-HDTMA-4.0 clay for nitrate and nitrite ion were 7.23 and 0.65 mg g−1, respectively, indicating that the organophilic clay obtained from the homoionic clay with 4 C.E.C. ion exchange and the surfactant HDTMA had significant effects on the adsorption of nitrate and nitrite ions.Finally, the possible mechanisms and implications of the results for the use of these organophilic clays as adsorbent materials for the removal of the ions under study are discussed.