Removal Of Ammonium Ions Research Articles

Katyon Değişim Reçinesi Kullanarak Sulu Çözeltilerden Amonyum Giderimi

Ammonium is one of the main factors responsible for eutrophication of water bodies. Purolite SSTC60 ion exchange resin was used to investigate its potential use on ammonium removal efficiency. The effects of important parameters affecting ion exchange such as ion exchange resin dosage, initial solution pH, temperature, mixing speed and initial ammonium concentration on ammonium removal were investigated. The highest ammonium removal was achieved at pH 7. It was determined that ammonium removal rates increased with resin dosage, mixing speed and temperature increase. It has been determined that temperatures higher than 20°C and mixing speed do not have a significant effect on ammonium removal efficiencies at equilibrium. It was observed that removal efficiencies decreased with increasing initial ammonium concentrations. Pseudo-first order and pseudo-second order kinetic equations were analyzed using nonlinear method to determine the most appropriate kinetic model for ammonium ion removal and found to be compatible with the pseudo-first order kinetic model. Finally, the evaluation of experimental data using nonlinear forms of Langmuir and Freundlich isotherm models determined that the adsorption data fit the Freundlich isotherm model rather than the Langmiur isotherm model.

The Influence of Zeolitic By-Product Containing Ammonium Ions on Properties of Hardened Cement Paste

Fluid catalytic cracking (FCC) catalysts, used in the petroleum industry, are sources of zeolitic by-products. These by-products are often used as sorbents for the removal of ammonium ions from wastewater. After a period of use, the zeolitic by-product loses its sorption properties and is no longer effective. The problem is the use of zeolitic by-product with ammonium ions. In this study, a zeolitic by-product containing ammonium ions and high contents of active SiO2 and Al2O3 was used as a supplementary cementitious material (SCM). Cement pastes containing 0.5%, 1%, 3%, 5%, and 10% of the by-product were prepared, and the compressive strength and density of the pastes were evaluated. Incorporation of the zeolitic by-product increased the cement strength by 17% and 32% after 7 and 28 days of hydration, respectively. Thus, incorporation of the zeolitic by-product with ammonium ions as an SCM has a complex effect on an ordinary Portland cement (OPC) system. Ammonium chloride accelerated cement setting after 7 days of hydration, and the pozzolanic reaction positively affected strength development after 28 days of hydration. The reaction products caused the cement to have a compact microstructure. The zeolitic by-product containing absorbed ammonium ions can be successfully reused to replace ordinary Portland cement in cement pastes.

Simultaneous removal of ammonium ions and sulfamethoxazole by ozone regenerated high silica zeolites

Continuous development of industry and civilization has led to changes in composition, texture and toxicity of waste water due to the wide range of pollutants being present. Considering that the conventional wastewater treatment methods are insufficient for removing micropollutants and nutrients to a high level, other, alternative, treatment methods should be used to polish wastewater treatment plant effluents. In this study we developed an alternative, polishing concept for removal of ammonium and micropollutants that could potentially be incorporated in existing wastewater treatment plants. We demonstrated a method to use high silica MOR zeolite granules as an adsorbent for simultaneous removal of the micropollutant sulfamethoxazole (SMX) and ammonium (NH4+) ions from aqueous solutions. At an initial NH4+ concentration of 10 mg/L the high silica zeolite mordenite (MOR) granules removed 0.42 mg/g of NH4+, similar to the removal obtained by commonly used natural zeolite Zeolita (0.44 mg/g). However, at higher NH4+ concentrations the Zeolita performed better. In addition, the Langmuir isotherm model showed a higher maximum adsorption capacity of Zeolita (qmax, 4.08 mg/g), which was about two times higher than that of MOR (2.11). The adsorption capacity of MOR towards SMX, at both low (2 µg/L) and high (50 mg/L) initial concentrations, was high and even increased in the presence of NH4+ ions. The used adsorbent could be regenerated with ozone and reused in consecutive adsorption–regeneration cycles with marginal decrease in the total adsorption capacity.

Ammonia removal from wastewater by air stripping and recovery struvite and calcium sulphate precipitations from anesthetic gases manufacturing wastewater

Anesthetic gas plant wastewater (AGPW) contains high concentrations of ammonia (NH3-N) and sulphate ions, which is known to results in severe environmental pollution in aquatic ecosystems without treatment. In the first stage of this study, a lab-scale investigation was done to improve removal of ammonia from AGPW by air stripping and struvite (or MAP: magnesium ammonium phosphate) precipitation processes, separately. The main operating parameters such as pH, air flow rate (L/min) and operating time were optimized for air stripping. The theoretical amount of removed ammonia via the air stripping process was calculated. The NH3-N removal efficiency reached 94 % at pH 12. On the other hand, the optimum ratio of [Mg2+]: [NH4+]: [PO43−] was determined to be 1:1.1:1.8 for the struvite precipitation. The concentration of NH3-N was reduced from 10,600 to 1680 mg/L at pH 8.0 and the corresponding removal efficiency was 84 % at optimum ration of MAP. The solution remained after the struvite precipitation was reacted with Ca(OH)2 at pH values in the range 10–13 for removal of sulphate in the second stage. The removal efficiencies at the optimum conditions were 98 % for sulphate, 31 % for COD and 20 % for TOC. Air stripping process and struvite precipitation could be considered an effective technology for removal and recovery of ammonia or ammonium ion (NH4+-N) from the AGPW. Surface analyses of the precipitated samples were characterized by SEM and XRD.

Evaluation of different forms of Egyptian diatomite for the removal of ammonium ions from Lake Qarun: A realistic study to avoid eutrophication

Three types of diatomite-based adsorbents—diatomaceous earth (DE), purified diatomite (PD), and diatomite@MgO/CaO (D@MgO) were used for adsorption decontamination of ammonium from Lake Qarun water (28.7 mg/L). The adsorption properties of the three diatomite-based adsorbents were evaluated by both batch and fixed-bed column adsorption studies. The kinetic results demonstrated removal percentages of 97.2%, 69.5%, and 100% using DE, PD, and D@MgO, respectively, at a 1 g/L adsorbent dosage. The adsorption results using DE and D@MgO showed the best fitness with pseudo-first-order kinetic and Langmuir isotherm models, while the obtained results using PD demonstrate better fitness with the Freunlidich model. The recognised fitting results with the pseudo-first-order model and estimated adsorption energies demonstrated physical uptake of ammonium by DE (5.93 kJ/mol), PD (4.05 kJ/mol), and D@MgO (7.81 kJ/mol). The theoretical maximum ammonium uptake capacity of DE, PD, and D@MgO were 63.16 mg/g, 59.5 mg/g, and 78.3 mg/g, respectively. Using synthetic adsorbents in a fixed-bed column system for treating ammonium ions in Lake Qarun water resulted in removal percentages of 57.4%, 53.3%, and 62.6% using a DE bed, PD bed, and D@MgO bed, respectively, after treating approximately 7.2 L of Lake Qarun water using a bed thickness of 3 cm, a flow rate of 5 mL/min, pH 8, and the determined ammonium concentration in Lake Qarun water (28.7 mg/L). The curves demonstrated breakthrough times of 900 min, 900 min, and 960 min for the DE bed, PD bed, and D@MgO bed, respectively, with 1440 min as the saturation time. The columns’ performances also were studied based on the Thomas model, the Adams-Bohart model, and the Yoon-Nelson model.

Pomegranate peel as a new low-cost adsorbent for ammonium removal

Since adsorption is one of the best ammonium removal methods, great efforts have been made to identify new low-cost and efficient adsorbents from agricultural waste and by-products due to their abundant availability, low-cost and eco-friendly advantages, in addition to the possibility of recycling ammonium back into agricultural processes. In this study, a series of batch experiments were performed to detect new bio-adsorbents for ammonium ions removal. Among the materials tested, pomegranate peel powder showed a high affinity to adsorb ammonium ions and, furthermore, available information on ammonium adsorption by this biomaterial is still missing from the literature. First, pomegranate peel powder was characterized by the determination of different parameters such as zeta potential, iodine number, Fourier-transform infrared spectroscopy analysis, scanning electron microscopy, particle size distribution and porosity. Then, the impact of various parameters, such as pH, contact time, stirring speed, adsorbent dose and adsorbate concentration in the adsorption process, was investigated. The highest ammonium removal capacity was obtained at pH = 4 using 400 mg of pomegranate peel powder and a stirring speed of 150 rpm for an initial concentration of ammonium of 30 mg/L. The system (adsorbent, adsorbate and solution) reached equilibrium after 2 h and the data fit well with the Langmuir model with a maximum monolayer adsorption capacity of 6.18 mg/g, while kinetics were well described by the pseudo-second-order model. These results introduce pomegranate peel powder as a promising bio-adsorbent to remove and recover ammonium from aqueous solutions.

Development of Synthetic Magnetic Zeolite Adsorbents and Application to Ammonium Ion Removal

Synthetic magnetic zeolite with Fe3O4 was developed and its adsorption performance of ammonium ions was examined. The influence of pH levels, Fe3O4 content of the magnetic zeolite, magnetization curve of the magnetic zeolite and isotherm curve were examined in batch type experiments. Magnetic zeolite synthesized by a hydrothermal process was observed with less than 12.6 wt% of Fe3O4 content by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. With the optimum pH level around 8, qe decreases linearly with the increase of Fe3O4 content. Additionally, the adsorption isotherm of ammonium ions is approximated by a Langmuir equation when the maximum adsorption was obtained at about 1.60 mmolg−1. Such processes as the substitution and thermal desorption methods were successfully introduced to regenerate the magnetic zeolite saturated by ammonium ions, which is shown to be easily separated by magnetic force. Thus, the magnetic zeolite is a potential adsorbent for the removal of ammonium ions with an easy separation method using a magnetic process.

Ammonium ion removal using activated zeolite and chitosan

AbstractStudies have previously been done on efficacies of chitosan and zeolite in ammonium ion (NH4+) removal. However, no study compares the adsorption performance of natural zeolite (NZ) and activated NZ (ANZ) with high molecular weight chitosan (HMWC) and low molecular weight chitosan (LMWC). Hence, this study investigates the potentials of NZ, ANZ, LMWC, and HMWC in NH4+ removal. The characteristics of NZ, ANZ, LMWC, and HMWC such as functional groups, surface morphology, elemental composition, zeta potential, and particle size was also investigated. The deposition of NH4+ on the surface of NZ and ANZ was confirmed with the absence of nitrogen by the adsorption spectrum of energy dispersive X‐ray (EDX) and supported by the presence of an Fourier transform infrared (FTIR) stretching band at ~3,500–3,300 cm−1, as well as broader and less intense bands ~1,600 cm−1 after the adsorption for all the adsorbents. The particle size of LMWC, HMWC, NZ, and ANZ were 98, 813, 22,354, and 9,826 nm, respectively. Meanwhile, after the activation process, the composition of O, Si, Al, Fe, Ca, and Na was reduced. NH4+ batch adsorption was also studied. HMWC, NZ, and ANZ reached adsorption equilibrium at 15 h, meanwhile for LMWC, the equilibrium reached at t = 20 h. The adsorption capacity of LMWC, HMWC, NZ, and ANZ at an initial concentration of 50 mg/L was 0.769, 0.331, 2.162, and 2.937 mg/g, respectively.

Treatment Assessment of Road Runoff Water in Zones filled with ZVI, Activated Carbon and Mineral Materials

Reducing the discharge of contaminants present in runoff water is important for a clean environment. This paper analyses field test results of three pilot-scale horizontal runoff water treatment zones filled with mixtures of zero valent iron (ZVI), activated carbon (AC), silica spongolite (SS), zeolite (Z), and limestone (LS). The investigated systems were (S1) ZVI/AC/SS, (S2) ZVI/AC/Z and (S3) ZVI/AC/LS. The efficiency of the three systems in the removal of Cd, Cu, Ni, Pb, Zn, COD and ammonium ions from runoff water was compared and the factors (temperature, pH, redox potential, hydraulic conductivity) and relationships affecting treatment effectiveness were determined. A statistical analysis of effluent contaminant concentrations and physicochemical parameters of effluent solutions included descriptive statistics, analysis of variance (ANOVA), a multidimensional analysis using a Principal Component Analysis (PCA), a factor analysis (FA) and a cluster analysis (CA). The ANOVA and cluster analyses indicated similarities between systems containing SS and LS. As a consequence, using cheaper SS can reduce investment costs. In addition, there were no significant differences between the three systems regarding Cd and Ni removal, while Cu and Pb were removed to almost 100%. The results indicate that all the tested materials supported ZVI and AC in the removal of heavy metals in a similar way. However, runoff water was enriched with nitrogen oxides and sulfates while flowing through treatment zones with SS and LS. The enrichment increased with increasing temperature and redox potential. The conducted analyses indicate that the most suitable mixture is ZVI/AC/Z. It should be emphasized that the ongoing processes (precipitation and ZVI corrosion) reduced the hydraulic conductivity of the filters up to two orders of magnitude. Expansive iron corrosion was the most limiting factor in ZVI filtration systems. In the future, applications decreasing the percentage of ZVI in the mixture are suggested.

Removal of ammonium ion from aqueous solutions by using unmodified and H2O2-modified zeolitic waste

In the petroleum industry during a catalytic cracking process, the used zeolitic catalyst becomes waste. This article investigated the sorption capacities of ammonium ions from aqueous solutions onto the previously mentioned zeolitic waste by batch experiments. Three types of zeolitic waste were used: unmodified zeolitic waste with two different particle size distributions and H2O2-modified zeolitic waste. Several techniques, including X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) multilayer adsorption theory measurements, and X-ray fluorescence analysis (XRF) were used to demonstrate experimentally that the zeolitic waste could be used as a sorbent for the water decontamination of NH4+ ions. The morphology of zeolitic waste investigated by scanning electron microscopy (SEM) revealed particles with a spherical shape. The nitrogen adsorption–desorption isotherms showed an isotherm mixture of types I (pure microporous) and IV (mesoporous). This suggested that the investigated zeolitic materials were mesoporous (4.84 nm) and microporous (0.852 nm), as well as containing slit/cylindric pores, according to a quench solid density functional theory (QSDFT) adsorption branch model. Zeolitic waste from the oil industry showed good NH4+ sorption properties (removal efficiency of 72%), thus becoming a potential adsorbent to be used in the treatment of contaminated aqueous effluents polluted with ammonium ions. Simultaneous waste and water decontamination can be achieved, providing a new tool and enhanced capabilities for environmental remediation.

Assessment of Constructed Wetlands’ Potential for the Removal of Cyanobacteria and Microcystins (MC-LR)

Microcystis blooms and the subsequent release of hepatotoxic microcystins (MCs) pose a serious threat to the safety of water for human and livestock consumption, agriculture irrigation, and aquaculture worldwide. Microcystin-LR (MC-LR), the most toxic variant of MCs, has been widely detected in a variety of environments such as water, sediments, plants, and many aquatic organisms. Conventional solutions of water treatment are costly, requiring specific infrastructure, as well as specialized personnel and equipment. Therefore, these solutions are not feasible in many rural areas or in the treatment of large reservoirs. In this regard, low-cost and low-technology solutions, such as constructed wetlands (CWs), are attractive solutions to treat surface waters contaminated with toxic cyanobacteria blooms from lakes, ponds, reservoirs, and irrigation systems. In line with this, the main aim of this work was to evaluate the potential of CWs for the treatment of water contaminated with MC-LR produced by Microcystis aeruginosa—LEGE 91094. For that, microcosms (0.4 × 0.3 × 0.3 m) simulating CWs were assembled with Phragmites australis to treat lake water contaminated with Microcystis aeruginosa cells and MCs. Results showed removal percentages of M. aeruginosa cells above 94% and about 99% removal of MC-LR during 1 week treatment cycles. CWs maintained their functions, regardless the presence of MC-LR in the system, and also showed significant removal of nutrients (ammonium ion removal up to 86%) and organic matter (removal reaching 98%). The present work indicates that CWs have the potential for removal of cyanobacterial cells and cyanotoxins, which can be useful for the treatment of eutrophic waters and provide water of sufficient quality to be used, for instance, in agriculture.

Removal of Ammonia from the Municipal Waste Treatment Effluents using Natural Minerals.

Due to various ecological problems, it is required to remove the ammonia nitrogen from wastewater. Industrial wastewater that was not subjected to any purification was used in this study, while most processes described in the literature were carried out using synthetically prepared solutions. The study investigated the removal of ammonium ions using ion exchange on various commercial minerals, in 3 h long batch ion-exchange experiments. Furthermore, research on the sodium chloride activation of the selected mineral was conducted. The screening of the mineral with the highest removal potential was conducted taking into account the adsorption capacity (q) and maximal removal efficiency (E), based on the NH4+ ions changes determined using the selective electrode and spectrophotometric cuvette tests. The highest adsorption capacity (q = 4.92 mg/g) of ammonium ions with the maximum removal efficiency (52.3%) was obtained for bentonite, with a 0–0.05 mm particle size. After pretreatment with a 1 mol/L NaCl solution, maximum efficiency increments were observed (55.7%). The Langmuir adsorption isotherm corresponds well with the equilibrium adsorption data (R2 from 0.97 to 0.98), while the Freundlich model was found to be mismatched (R2 = 0.77). Based on these results it was concluded that natural sorbents may be effectively applied in wastewater treatment. It can be observed that as the size of sorbent particles gets lower, the adsorption capacity, as well as the removal efficiency, gets higher. The bentonite pretreatment with the NaCl solution did not result in the expected efficiency improvement. The 2 mol/L solution affected about 3.5% of the removal efficiency yield.

Treatment of By-Products Generated from Anaerobic Digestion of Municipal Solid Waste

PurposeThis study aimed to examine the possibilities of the treatment of the by-products generated in the anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW): oxygen stabilization (composting) of the solid digestate and pretreatment with air stripping of the effluents (liquid digestate and leachate from maturation field and reactors from composting).MethodsOxygen stabilization (OS) was performed in full-scale in a mechanical–biological treatment (MBT) plant using three different methods, using an open field or enclosed box reactor with aeration. The ammonia stripping was performed in a pilot-scale installation using effluents from AD (liquid digestate) and OS (leachate from maturation field and reactors).ResultsThe lowest self-heating possibility after the OS was recorded at 28.5 °C, which proves that the most stabilized was the sample after processing with structuring material addition. Due to air stripping, the highest efficiency of ammonium ions removal was noted at the level of 50.6%, with an initial pH value of 10.5, after 12 h. Among the examined factors pH value was found to be significant [the determination coefficient (R2) of 0.93].ConclusionsThe oxygen stabilization of the digestate requires the structuring material addition before being placed in the reactor with aeration. The inert fraction from the ballistic separation of the OFMSW can be an interesting solution, as required structuring material. Air stripping as the effluents pre-treatment step can meet the MBT plants expectations.Graphic

Formation of chlorination by-products in drinking water treatment plants using breakpoint chlorination

In drinking water treatment plants generally chlorination is applied for disinfection using Cl2, ClO2, or NaOCl reagents. In Hungary due to the relatively high ammonium ion concentration of source water originating from deep aquifiers, not only the disinfection but simultaneously the ammonium ion removal is also a crucial task to prevent the nitrite formation. For this purposes the breakpoint chlorination is used which needs approximately 10 times more chlorine than the disinfection resulting in enhanced formation of organic and inorganic by-products. Chlorination by-product formation was investigated in twelve drinking water treatment plants applying breakpoint chlorination. Trihalomethanes were detected in the highest concentration (14.7 μg/L to 143 μg/L), followed by haloacetic acids and haloacetonitriles. In 50% of the investigated water treatment plants, the concentration of trihalomethanes in finished water exceeded the Hungarian parametric value, but it was the same range as in water supplies using chlorine for disinfection. The concentration of trihalomethanes, haloacetic acids, haloacetonitriles and adsorbable organic halides in finished water was found to correlate with residual free chlorine (r > 0.5) and raw water temperature (r > 0.48). At high bromide concentration (cBr- > 0.2 mg/L) of the raw water the proportion of brominated by-products (trihalomethanes and haloacetic acids) increased up to 50%. Chlorate concentration was particularly high at drinking water treatment plants using hypochlorite (0.66–2.0 mg/L).By-products are mostly generated at breakpoint chlorination, but their additional formation within the water distribution system is also significant, especially where the concentration of free chlorine is high and the residence time is long. Elimination (potentially biodegradation) of haloacetic acids and haloacetonitriles was observed at several sampling sites. The efficiency of the granulated activated carbon filters in removing adsorbable organic halides, trihalomethanes and haloacetic acids amounted generally under 25%.

Ammonium removal and recovery from real digestate wastewater by a modified operational method of membrane capacitive deionization unit

In this study, an extensive examination of ammonium removal and recovery from highly concentrated digestate wastewater was systematically performed. The treatability and ammonium recovery potential of the real digestate wastewater was assessed by enhanced Flowed Channel Membrane Capacitive Deionization (fcMCDI), which was introduced in our previous study. The fcMCDI cell was found efficient to remove ammonium ions from a synthetic mixture of glucose and Ca2+and Na+ ions, which are the major components of the anaerobic digestate liquid. Specific ammonium removal performance of the system was investigated in the presence of other ions. In a single cycle experiment, the process was able to remove the Mg2+, Ca2+, K+ and NH4+ ions from real digestate wastewater at percentages of 90.4%, 85%, 67.9% and 54.4%, respectively. A comparison of the conventional MCDI operation with an increased voltage application method with the fcMCDI cell was presented. Ammonium was successfully recovered in the form of ammonia gas by increasing the cell's working voltage, and simultaneous deionization of the other ions in the digestate wastewater was achieved. The obtained ammonium removal efficiencies were 89% and 67% with synthetic and real digestate wastewater, respectively. The results demonstrated that the enhanced MCDI technology holds a great potential to be an energy-efficient process for ammonium removal and recovery while also removing other contaminants effectively from highly concentrated wastewater sources.

Ammonium ion removal from aqueous solutions using fly ash derived zeolites by alkaline fusion

In this study, fly ash (FA) with different chemical compositions was converted into zeolites by a fusion method, as confirmed by Fourier-transform infrared spectroscopy (FTIR). FA was obtained from three different thermal power plants in Bosnia and Herzegovina: Ugljevik, Stanari and Gacko. In the FA spectrum, a quite wide absorption band was observed at 1097 cm-1, while in those of the synthesized zeolites, this absorption band is narrowed and elongated and displaced toward 972 cm-1. These characteristic bands can be attributed to substitution of Si4+ with Al3+ in the tetrahedron, during the formation of alumosilicate and their interaction with Na+ ions. Chemical analysis has shown that the dominant component was SiO2 in the FA Ugljevik (UF) and FA Stanari (SF) with mass fractions of - 36.43 and 48.18 %, respectively and CaO in the FA Gacko (GF) with the mass fraction of 65.89 %. In studies of ammonium ion adsorption equilibrium was achieved after 24 h in zeolites of UF and SF, while for the GF sample it was necessary 48 h to reach the equilibrium. Kinetic studies of have shown that the adsorption process on all zeolites followed the Elovich model with high values of the coefficient of determination. The largest amounts of adsorbed ammonium ions were measured at the pH 8 amounting to 5.98, 6.54 and 4.23 mg NH?+/g zeolite for UF, SF and GF, respectively. Examination of adsorption isotherms have shown the better agreement of the obtained results with the Langmuir model for the SF zeolite sample, and the Tempkin model for the UF and GF zeolite samples. Regenerated zeolites have shown similar adsorption capacities for ammonium ions (for UFr 10.3 mg/g; for SF 12.0 mg/g; for GFr 7.8 mg/g) as initial zeolites (for UF 12.2 mg/g; for SF 12.1 mg/g; for GF 14.3 mg/g). Examination of adsorption isotherms of regenerated samples has also shown the best agreement with the Langmuir model for all regenerated samples. The obtained similar and even higher removal percentages of ammonium ions from a real sample of wastewater by using regenerated zeolites (for UFr 60.7 %; for SFr 55.2%; and for GFr 30.7 %) as compared to the initial ones (for UF 45.1 %; for SF 60.6%; for GF 26.0 %) show potentials of the synthesized zeolites from fly ash for ammonium ion removal from wastewaters.

Removal of Ammonium Ions and Ammonia from Groundwater by Oxidation Processes

The process of removal of ammonium ions and ammoniafrom ground water, which contained these components in quantities exceeding the maximum permissible limit, was studied by the oxidation method. It was shown by the CG-MS method and thin layer chromatography that calcium hypochlorite in certain amounts and at certain pH values oxidizes ammonium ions and ammonia, presumably with the formation of free nitrogen, without forming chloramines, reducing concentration of ammonium ions and ammonia to values below the maximum allowable limit for drinking water.

ADSORPTION OF AMMONIA BY BASE ACTIVATED BENTONITE CLAY KINETIC AND EQUILIBRIUM STUDIES

Nitrogen compounds are essential elements for living organisms. The increased concentration of ammonia in ionized (NH4+) and non-ionized form (NH3) in surface waters causes negative effects on aquatic organisms, since it enters into the nitrogen cycle, and thus contributes to the eutrophication of water. The presence of higher concentrations of ammonia in surface waters than natural ones is the result of faecal contamination through the sewage system or runoff from arable areas which were treated with fertilizer. Water contaminated with ammonia can be purified by various methods: biological (nitrification-denitrification method), oxidation with chlorine, chemical precipitation, membrane filtration, etc. One of the alternative methods is removal by adsorption with natural materials such as clay and zeolite. Bentonite clay was marked off as a suitable adsorbent of cationic pollutants due to the permanent negatively charged surface. Тhe textural properties (specific surface, porosity) and structural properties of bentonite clay (the distance between the layers, the type of ions in the space between the layers) and consequently its adsorption capacity for pollutants is changed with the activation by acid or base and intercalation. There is very little literature data on the application of bentonite clay for removal of ammonium ions. Therefore, the aim of this work is activating the raw bentonite clay with a base and its application as an adsorbent for removal of ammonium ions from aqueous solutions. The influence of the adsorption conditions (adsorbent dose, temperature, pH, adsorbate concentration and contact time) on the amount of removed ammonia from the aqueous solution was investigated. Equilibrium data were analyzed by Langmuir, Freundlich and Dubinin-Radushkevich isotherms. The best agreement with experimental data was obtained by Langmuir isotherm (R2 = 0.987). The following kinetic models were applied: the pseudo-first order, pseudo-second order, and the intra-particle diffusion model. The pseudo-second order model is most suitable for describing the adsorption of ammonium ions onto the base activated bentonite from aqueous solutions (R2 = 0.997). Removal of ammonium ions by activated clay is a pH-dependent and endothermic process, the adsorption degree of pollutants is increased with rising temperature. The highest adsorption capacity of the base activated bentonite clay of 26.82 mg/g was obtained in a solution of pH 6 and a temperature of 40 °C, at an adsorbent dose of 2 g/dm3 and аt an adsorbate concentration of 100 mg/dm3. By activating the adsorbent in a 1 M NaOH solution, the adsorption ability of the bentonite clay towards ammonium ions is improved. The results of this study show that the base activated bentonite clay is a potential adsorbent material for ammonia, i.e. ammonium ions.

Preparation, characterization, and performance of 4A zeolite based on opal waste rock for removal of ammonium ion

In this study, 4A zeolite was prepared from opal waste rock by hydrothermal method and applied in ammonium ion adsorption. To optimize synthesis conditions, the effect of crystallization time (1–8 h), crystallization temperature (65–115°C), Na2O/SiO2 (0.6–2.0), H2O/Na2O (20–70), and SiO2/Al2O3 (1.0–3.5) was investigated. X-ray diffraction, scanning electron microscope imaging, cation exchange capacity, static water adsorption, Fourier transform infrared spectroscopy, and N2 adsorption–desorption isotherm were used for assessing properties of 4A zeolite. Adsorption experiments were performed by 1.0 g l−1 4A zeolite with NH4+ solution (5–300 mg l−1) for 4 h at room temperature. The experiment results revealed with a crystallization time of 3 h, a crystallization temperature of 85°C, Na2O/SiO2=1.0, H2O/Na2O = 40, and SiO2/Al2O3=2.0, the 4A zeolite synthesized had excellent performance with cation exchange capacity of 2.93 mmol (g dry zeolite)−1 and static water adsorption of 22.3%. The adsorption process was described by Freundlich model (R2>0.99) and the maximum adsorption capacity could reach to 53.11 mg g−1. The experimental results provided a novel approach for the utilization of opal waste rock, which is produced during the mining of opal-rich palygorskite, and for the synthesis of 4A zeolite and the removal of ammonium ion.

Role of ammonium ions on the stability of TiO2 sol

In this paper, the role of the trace ammonium ions on the stability of TiO2 sol prepared by peroxo titanic acid (PTA) sol was investigated. The results showed that the removal of ammonium ions in PTA sol is beneficial to reduce agglomeration and increase the negative charge on the surface of TiO2 colloidal particles, contributing to the higher stability and longer storage time of the TiO2 sol. It was also approved by the increase of interaction energy calculated by classical DLVO theory. In addition, the photocatalytic performance of TiO2 sol was improved due to the decrease of aggregation of TiO2 colloidal particles.