Adsorption Study for the Removal of Nitrate from Water Using Local Clay

Ultrasonic-Assisted Nitrate Anion Incorporation in Triaminoguanidium Chloride Based Covalent Organic Polymer for Methylene Blue Dye Adsorption

Terephthalaldehyde-triaminoguanidium chloride covalent organic polymer, Te-TGCl COP can facilely be incorporated with NaNO3 by sonication. Te-TGCl COP incorporated with NaNO3 via ultrasonication adsorbs Methylene Blue (MB) dye. Te-TGCl COP alone shows negligible adsorption capacity for MB, however, when treated with NaNO3, its adsorption capacity emerges slightly. Moreover, ultrasonication of the NaNO3 treated COP, Te-TG-NaNO3 COP shows dramatic increase in its adsorption capacity for MB (qe for Te-TGCl COP ≈0 mg g-1; for Te-TG-NaNO3=17.65 mg g-1). Emergence of MB dye adsorption property in Te-TG-NaNO3 COP composite may be attributed primarily to the electrostatic interaction of MB dye molecules with nitrate anions and the sonochemical effect caused fibrous morphological structure of the adsorbent material. The kinetics of MB dye adsorption onto Te-TG-NaNO3 COP composite exhibits an excellent fit for the pseudo-second order model, suggesting the rate-determining step to be chemisorption. Homogeneous monolayer adsorption of MB dye onto Te-TG-NaNO3 COP composite can be suggested as the Langmuir isotherm model seemed to be fitted well.

Anion-Exchange Electrospun Mixed-Matrix Polymer Fibers of Colesevelam for Water Treatment

Novel anion-exchange electrospun fiber membranes of polycaprolactone doped with the cationic, cross-linked colesevelam polymer are reported. The weight fraction of cross-linked cationic colesevelam polymer, as the active phase within the PCL matrix, can readily be controlled in the synthesis of the mixed-matrix fibers (Cole@PCL), enabling optimization of the ion-exchange properties of the resulted membranes. This approach enabled adaptation of anion-exchange resins to a permeable, flexible membrane form, which is a significant advancement toward futuristic water treatment applications, demonstrated herein for the removal of trace contaminants, including nitrates and phosphates, as well as anionic dyes. The Cole@PCL membranes demonstrated the dependence of contaminant uptake on the weight percentage of colesevelam in the mixed-matrix membrane. An optimal 10 wt % of colesevelam was identified, demonstrating a staggering ion removal capacity of 155.8 mg/g for nitrate, 177.6 mg/g for phosphate, and 70 mg/g for Methyl Orange.

Removal of lead ions from aqueous solution using new magnetic metal-organic framework

In this research, new magnetic nanocomposites that consist of NH₂-MIL53 (Al) and Fe₃O₄ nanoparticles functionalized with cysteine were synthesized and characterized. The application of these nanocomposites was investigated to remove lead ions from the wastewater model. The concentration of metal ions was measured by the utilization of flame atomic absorption spectroscopy (FAAS). Also, XRD, SEM, EDX, and FTIR instruments were used to identification and characterization of the synthesized nanocomposites. The effect of operating parameters such as; pH, contact time and adsorbent dosage were investigated on lead removal. The synthesized nanocomposite showed great potential for lead removal. The maximum adsorption capacity of the nanocomposite was about 361.53 mg/g. Adsorption kinetic parameters well fitted with the pseudo-second order kinetic model. The reusability test of the synthesized magnetic absorbent showed good adsorption efficiency for at least three consecutive cycles.

Adsorption of nitrate from interflow by the Mg/Fe calcined layered double hydroxides

Nitrate loss in interflow caused serious nitrate pollution of neighboring water bodies in the purple soil region of China's Sichuan Province. In this study, Mg/Fe(Al)-calcined layered double hydroxides (Mg/Fe(Al)-CLDHs) with varied Mg/Fe(Al) ratios were synthesized for nitrate removal from interflow, and 3:1 Mg/Fe CLDH exhibited the best adsorption performance. The effects of initial pH, adsorbent dosage and co-existing anions on the adsorption performance were investigated by batch experiments. The best-fitting kinetic and isothermal models for nitrate adsorption were the pseudo-second-order model and Freundlich model, respectively, indicating that the adsorption process was a physical-chemical multilayer process. The maximum adsorption capacity of nitrate was 73.36 mg/g, which was higher than that of many other commonly used adsorbents. The adsorbents were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) techniques, and the XRD and FT-IR results revealed that the adsorption mechanism involved original layered structure reconstruction and ion-exchange interaction. Under the coexistence of SO₄^2- and Cl^-, 75.63% nitrate in interflow could be removed after 6 h of adsorption. Overall, the synthesized Mg/Fe CLDH is an effective and low-cost nitrate adsorbent for in-situ nitrate removal.

Attenuation of nitrate from aqueous solution using raw and surface modified biosorbents from Adansonia digitata fruit pericarp

The prevalence of nitrate in potable water is a serious environmental concern. Several methods for eliminating nitrate from water have been made and implemented. During the course of this research, raw (RADFP) and surface-modified fruit pericarp (SMADFP) biosorbents derived from the Adansonia digitata plant were applied in order to remove nitrate from an aqueous solution. The external features of the biosorbents were studied with the aids of SEM and BET. The FT-IR spectrometer was utilized for identification of the functional groups of the adsorbents. A UV-Vis device was used to quantify the nitrate concentration. The adsorbents under investigation exhibit a heterogeneous pore structure with a considerable number of mesopores, with surface areas of 361.527 and 379.877 m² per gram for RADFP and SMADFP, respectively. FT-IR spectra revealed the presence of carboxyl, hydroxyl, carbonyl, and halogen groups on the adsorbent. The maximum nitrate removal efficiencies of RADFP and SMADFP were 64.55 and 88.95%, respectively. The maximum adsorption efficiencies are achieved when the pH is 2, the starting concentration is 27.50 mg/L, the contact period is 75.00 min, and the amount of biosorbent is 5.50 g. RADFP and SMADFP have a removal capacity of 12.45 as well as 25.18 mg per gram and adsorption intensity of 3.2300 and 5.4500, respectively. The investigational values for the elimination of nitrate ions concurred well to both Freundlich and Langmuir models with R² values of 0.99917 and 0.99763 for RADFP and SMADFP, respectively, and pseudo-second-order kinetic model with R² values of 0.99817 and 0.99947, respectively for RADFP and SMADFP. It can be concluded that SMADFP is a relatively better biosorbent than RADFP, which will be utilizable for the remediation of nitrate from an aqueous solution.

Nitrate adsorption onto surface-modified red mud in batch and fixed-bed column systems: equilibrium, kinetic, and thermodynamic studies

This research aimed to develop a novel composite as a low-cost adsorbent for the removal of nitrate ion from aqueous solutions. The characterization of this composite (composition of red mud with dimethyldioctadecylammonium bromide (DDAB)) was performed by XRF, XRD, FTIR, and BET analyses. The most influential variables on nitrate adsorption, including contact time, solution acidity, adsorbent amount, and temperature were studied. The maximum amount of nitrate adsorbed onto the prepared adsorbent was obtained at pH 5.5 and contact time 30 min. The heterogeneous adsorption occurred during the uptake of nitrate. The results of kinetic study revealed that intra-particle diffusion was the major limitation for nitrate adsorption rate. The values of thermodynamic parameters illustrate the non-spontaneous, associative, and exothermic adsorption process. Increasing the temperature enhances the tendency of the process to non-spontaneously. Research on fixed-bed column has been done under different initial nitrate concentrations. The adsorption capacity of nitrate was increased with an increase in the initial concentration of nitrate. The results of column data were successfully explained using the Thomas and Yoon-Nelson models.

Modified Hazelnut Shells as a Novel Adsorbent for the Removal of Nitrate from Wastewater

The aim of the study was to prepare a novel adsorbent by chemical modification of hazelnut shells and evaluate its potential for the nitrate removal from model solutions and real wastewater. The characterization of the novel adsorbent, i.e., modified hazelnut shell (MHS) was performed. The adsorbent characterization included the analysis of elemental composition and the surface characteristics analysis by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The adsorption experiments (batch technique) were performed to investigate the effects of adsorbent concentration, contact time, initial nitrate concentration, and solution pH. The nitrate removal efficiency increased with the increase in MHS concentration and decreased with the initial nitrate concentration. MHS was found to be effective in nitrate removal over a wide pH range (from 2 to 10), and the highest amount of nitrate adsorbed was 25.79 mg g−1 in a model nitrate solution. Depending on the aqueous medium (model solutions or real wastewater samples), it was shown that both Langmuir and Freundlich adsorption isotherm models can be used to interpret the adsorption process. It was found that the kinetics are well described by a pseudo-second order model and the nitrate adsorption process can be controlled by chemisorption. The intraparticle diffusion model has been used to identify an adsorption-controlled process by diffusion mechanisms. Adsorption/desorption experiments in column confirmed that MHS could be successfully used in multiple cycles (at least three), indicating the potential of MHS as an alternative to costly commercial adsorbents for the removal of nitrates from wastewater.

Nitrate Water Contamination from Industrial Activities and Complete Denitrification as a Remediation Option

Freshwater is a scarce resource that continues to be at high risk of pollution from anthropogenic activities, requiring remediation in such cases for its continuous use. The agricultural and mining industries extensively use water and nitrogen (N)-dependent products, mainly in fertilizers and explosives, respectively, with their excess accumulating in different water bodies. Although removal of NO3 from water and soil through the application of chemical, physical, and biological methods has been studied globally, these methods seldom yield N2 gas as a desired byproduct for nitrogen cycling. These methods predominantly cause secondary contamination with deposits of chemical waste such as slurry brine, nitrite (NO2), ammonia (NH3), and nitrous oxide (N2O), which are also harmful and fastidious to remove. This review focuses on complete denitrification facilitated by bacteria as a remedial option aimed at producing nitrogen gas as a terminal byproduct. Synergistic interaction of different nitrogen metabolisms from different bacteria is highlighted, with detailed attention to the optimization of their enzymatic activities. A biotechnological approach to mitigating industrial NO3 contamination using indigenous bacteria from wastewater is proposed, holding the prospect of optimizing to the point of complete denitrification. The approach was reviewed and found to be durable, sustainable, cost effective, and environmentally friendly, as opposed to current chemical and physical water remediation technologies.

Introduction of nitrogen doped graphene nanosheets as efficient adsorbents for nitrate removal from aqueous samples

PURPOSE

Introducing and developing new kinds of adsorbents are always a significant challenge in water treatments. In this work, for the first time, graphene oxide (GO), nitrogen-doped graphene oxide (ND-GO), highly nitrogen-doped graphene oxide (HND-GO), and 3D high nitrogen-doped graphene oxide (3D-HND-GO) were synthesized and comparatively evaluated in the removal of nitrate content of tap and underground waters.

METHODS

The removal of the target analyte was performed through a batch adsorption approach, and the factors influencing its removal efficiency (i.e., initial pH of the sample, primary concentrations of nitrate, amount of adsorbent, and contact time) were evaluated through a central composite design (CCD) and response surface methodology (RSM).

RESULTS

Based on the results, 3D-HND-GO showed the highest removal efficiency in comparison with the other mentioned nanoparticles. The nitrate removal using this adsorbent was modeled successfully so that R 2, adjusted R 2, and predicted R 2 values were 0.9717, 0.9508, and 0.9010, respectively. In addition, the optimal removal condition was achieved using the Nelder-Mead non-linear optimization algorithm as follow: the initial concentrations of nitrate (expressed as nitrogen): 15.0 mg/mL, the amount of the adsorbent: 2.0 mg/mL; pH of the sample: 3.0; and the contact time: 20.0 min. Under this optimal condition, the actual removal result (92.5 ± 4.0%) was in good agreement with the expected value (94.8 ± 5.1%). Additional studies were also performed to comprehensibly evaluate the adsorption activity of the adsorbent (e.g., kinetic, isotherm, and desorption parameters). The adsorption isotherm complied with the Langmuir model illustrating the considerable mono-layer adsorption capacities for the target ions with qm of 8.7 mg/g. The adsorption process was indicated to obey a pseudo 2nd order kinetic model, with the rate-limiting step for the adsorption phase.

CONCLUSIONS

This study revealed which 3D-HND-G leads to improved yield in the nitrate ions elimination, particularly at acidic media, which was related to the enhanced dispersibility and larger surface area. The adsorbent was further successfully used for treating tap and underground water samples. At the present moment, research as grown to modify 3D-HND-G in orders to increase the potentiality for industrial applications.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40201-021-00741-7.

Plasticized magnetic starch-based Fe3O4 clay polymer nanocomposites for phosphate adsorption from aqueous solution

Plastics contribute a magnificent role to modern civilization, but the waste becomes a huge burden to ecology and remains intact for a thousand years. Hence, the recent movement is shifted to biodegradable plastic. In this study, an attempt was made to introduce an added value to the environment where the bio-plasticized materials were used for phosphate removal. A G-plasticized magnetic starch-based Fe₃O₄ clay polymer nanocomposite (PNC) was synthesized to remove phosphate from the aqueous solution. It was synthesized from activated carbon (AC), coated iron oxide nanoparticles (CIONP), nanoclay (NC), and glycerol (G) as a plasticizer. The synthesized adsorbents were characterized with UV-Vis, SEM, XRD, and FTIR. The PNC and constituent (CIONP) were tested for phosphate removal through batch adsorption experiments. The adsorption capacity increases with increasing the adsorbent dose and decreases with an increase in phosphate concentration. The synthesized PNC effectively raised the constituent optimum phosphate ion adsorption pH from acidic (pH = 3) to slightly acidic (pH = 6). At the optimal pH, the CIONP and PNC maximum phosphate adsorption capacity (MPAC) was 3.12 and 2.31 mg P/g, respectively. In addition, the phosphate removal efficiency of PNC (45-95% at pH 6) was comparable to CIONP (58-97% at pH 3) under an initial 2–100 mg P/L. The adsorbents adsorption kinetics and isotherm study best described by the pseudo-second-order and Freundlich model, in turn. The SEM images support the conclusion, in which the PNC shows a heterogenous porous surface. Therefore, the adsorption mechanisms were mainly described by multilayer and chemical adsorption, such as electrostatic and ion exchange. It can be concluded that there is a positive synergistic effect between the biopolymer (starch) and nanomaterials that form the PNC. This study results propose the multiple added values of modified bio-plasticized material (with adsorbent) for environmental (phosphate) remediation.

Adsorption Studies on Magnetic Nanoparticles Functionalized with Silver to Remove Nitrates from Waters

This paper presents a novel procedure for the treatment of contaminated water with high concentrations of nitrates, which are considered as one of the main causes of the eutrophication phenomena. For this purpose, magnetic nanoparticles functionalized with silver (Fe3O4@AgNPs) were synthesized and used as an adsorbent of nitrates. Experimental conditions, including the pH, adsorbent and adsorbate dose, temperature and contact time, were analyzed to obtain the highest adsorption efficiency for different concentration of nitrates in water. A maximum removal efficiency of 100% was reached for 2, 5, 10 and 50 mg/L of nitrate at pH = 5, room temperature, and 50, 100, 250 and 500 µL of Fe3O4@AgNPs, respectively. The characterization of the adsorbent, before and after adsorption, was performed by energy dispersive X-ray spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller analysis and Fourier-transform infrared spectroscopy. Nitrates can be desorbed, and the adsorbent can be reused using 500 µL of NaOH solution 0.01 M, remaining unchanged for the first three cycles, and exhibiting 90% adsorption efficiency after three regenerations. A deep study on equilibrium isotherms reveals a pH-dependent behavior, characterized by Langmuir and Freundlich models at pH = 5 and pH = 1, respectively. Thermodynamic studies were consistent with physicochemical adsorption for all experiments but showed a change from endothermic to exothermic behavior as the temperature increased. Interference studies of other ions commonly present in water were carried out, enabling this procedure as very selective for nitrate ions. In addition, the method was applied to real samples of seawater, showing its ability to eliminate the total nitrate content in eutrophized waters.

Nitrate removal from aqueous solutions by adsorption onto hydrogel-rice husk biochar composite

In the present study, we investigated the performance of hydrogel-rice husk biochar composites, as low-cost, alternative, and biocompatible adsorbents for separating nitrate ions from aqueous solutions. Hydrogel-biochar composite was synthesized at dosages of 2.5%, 3.6%, 4.8%, and 9.6% weight ratios of biochar. The composite was characterized by several common methods including FTIR, SEM, TEM, TGA, and DSC. In addition, the effect of contact time, initial concentration of nitrate ions, and solution pH were considered. The maximum removal of nitrate was about 34.3% at acidic pH (pH = 3) using 0.02 g of adsorbent in 25 ml of nitrate solution with the initial concentration (20 mg/L) and temperature of 25°C for 60 min. Based on the findings, 5% biochar in the composite was the optimal dosage. Adsorption kinetic study revealed that this process followed the first-order kinetic model. The experimental equilibrium adsorption data were tested by the Temkin isotherm model with R²  > 0.97. Based on the thermodynamic studies, the adsorption process was endothermic and spontaneous. Overall, the results suggested that the obtained composite can be specifically employed for removal of contaminations from aqueous solutions. PRACTITIONER POINTS: Hydrogel-biochar composite provides a biocompatible and cost-effective adsorbent. Hydrogel-biochar composite was applied to eliminate nitrate from aqueous solutions. Nitrate removal increased in the synthesized composite upon elevation of the weight ratio of biochar to 0.2 g.

Mg-Fe layered double hydroxide with chloride intercalated: synthesis, characterization and application for efficient nitrate removal

Mg-Fe layered double hydroxide intercalated with chloride (Mg-Fe-Cl LDH) was synthetized, characterized, and evaluated as adsorbent to remove nitrate from aqueous solution. The pH, initial nitrate concentration, adsorbent dosage, and particle size were investigated. Kinetic data was best represented by pseudo-second order model indicating that the rate limiting step was chemisorption. Intraparticle diffusion model indicates that adsorption kinetic is limited by external and intraparticle diffusion. Sips model was selected, based on R², ARE, and AIC, to adequately represent the adsorption isotherms, which permits to affirm that the adsorption occurs in heterogeneous surface, obtaining the maximum adsorption capacity of 18.17 mg.g^-1 at 30 ^oC. Thermodynamics parameters indicate that the adsorption was spontaneous, exothermic, and with structural modification. These findings come up with Mg-Fe-Cl LDH as a suitable adsorbent for nitrate and could contribute to its removal from the water and wastewater.