Synthesis and characterization of a single phase zeolite A using coal fly ash

Efficiency, mechanism and application prospect of ammonium adsorption and desorption over a sodium-acetate-modified synthetic zeolite

Adsorption is an effective approach for remediating ammonium pollution, and zeolite has exceptional efficacy for the adsorption of ammonium. The investigation of ammonium adsorption using coal-fly-ash-based zeolite has gained remarkable attention in contemporary research. In this work, a sodium-acetate-modified synthetic zeolite (MSZ) was used to absorb ammonium in simulated wastewater. The MSZ had an adsorption capacity for ammonium of 27.46 mg g-1, and the adsorption process followed the Langmuir isotherm model and pseudo-second-order kinetics model. The adsorption and desorption of ammonium were controlled by ion exchange, pore diffusion, and electrostatic attraction processes. Ion exchange was responsible for 77.90% of the adsorption process and 80.16% of the desorption process. The MSZ was capable of continuously removing large amounts of ammonium from wastewater through fixed bed adsorption. After 5 regeneration cycles, MSZ still maintained 75% adsorption characteristics for ammonium. Using MSZ adsorbed with ammonium as a soil amendment increased the germination rate of mung beans by 10%. Furthermore, it also increased the stem length, root length, and fresh weight by 20-30%. These findings suggest that MSZ provides a promising application prospect to mitigate ammonium pollution and recycle ammonium resources.

The Removal of Strontium Ions from an Aqueous Solution Using Na-A Zeolites Synthesized from Kaolin

Sr2+ ions in an aqueous solution were removed using Na-A zeolites synthesized from kaolin, a natural mineral. Na-A zeolites with high crystallinity were synthesized using NaOH/kaolin mass ratios of 0.6 (ZK06) and 0.9 (ZK09). The adsorption reached equilibrium within 120 min. The adsorption data obtained from experiments for Sr2+ using ZK06 and ZK09 were appropriately analyzed with pseudo-second-order kinetic and Langmuir isotherm models. Comparing the maximum adsorption capacities (qm) of ZK06 and ZK09 for Sr2+, the highest values were obtained at 1.90 and 2.42 mmol/g, respectively. Consequently, the Na-A zeolites synthesized from kaolin can be evaluated as adsorbents with high adsorption capacities for the removal of Sr2+, proportional to the degree of their crystallinity.

Sonocrystallization of a novel ZIF/zeolite composite adsorbent with high chemical stability for removal of the pharmaceutical pollutant azithromycin from contaminated water

Water pollution management, reduction, and elimination are critical challenges of the current era that threaten millions of lives. By spreading the coronavirus in December 2019, the use of antibiotics, such as azithromycin increased. This drug was not metabolized, and entered the surface waters. ZIF-8/Zeolit composite was made by the sonochemical method. Furthermore, the effect of pH, the regeneration of adsorbents, kinetics, isotherms, and thermodynamics were attended. The adsorption capacity of zeolite, ZIF-8, and the composite ZIF-8/Zeolite were 22.37, 235.3, and 131 mg/g, respectively. The adsorbent reaches the equilibrium in 60 min, and at pH = 8. The adsorption process was spontaneous, endothermic associated with increased entropy. The results of the experiment were analyzed using Langmuir isotherms and pseudo-second order kinetic models with a R2 of 0.99, and successfully removing the composite by 85% in 10 cycles. It indicated that the maximum amount of drug could be removed with a small amount of composite.

Synthesis of NaA zeolite from foundry dust and its adsorption capacity of ammonia

Eutrophication of water bodies due to excess ammonia nitrogen (NH₄⁺-N) is harmful to aquatic organisms and human health. In this study, foundry dust (FD) from foundry industry was used to synthesize NaA zeolite to use as an adsorbent to remove NH₄⁺-N from wastewater. Results demonstrate that FD could be successfully synthesized to form a foundry dust-based NaA zeolite (FZA) through adjustment of the silica-alumina ratio of n (SiO₂)/n (Al₂O₃) at 2 at 95 °C. Specific surface area, total pore volume, and cation exchange capacity (CEC), and maximum adsorption NH₄⁺-N of FZA was respectively 43.185 cm²/g, 0.0364 cm³/g, 212.35 mmol/100 g and 37.81 mg/g, which was 4.74, 1.54, 1.52 and 1.62 times as much as the NaA zeolite (SZA). FZA with higher adsorption NH₄⁺-N capacity was related to higher specific surface area and CEC. The NH₄⁺-N adsorption amount of 28.57 mg/g by FZA was obtained after the fourth regeneration, which was notably higher than that of SZA (23.27 mg/g). The desorption rate of NH₄⁺-N from FZA was 87% by the fourth regeneration. FZA effectively removed NH₄⁺-N from swine wastewater containing 153.32 mg/L NH₄⁺-N. Results suggest that FZA could be used as absorbent to removal NH₄⁺-N from wastewater.

Synthesis of zeolite A from fly ash and its application in the slow release of urea

The study focused on the transformation of coal fly ash to zeolite A (ZA) as a potential carrier for the slow release of urea. After being treated with HCl aqueous solution and NaOH successively, SiO₂ and Al₂O₃ were converted into sodium silicoaluminate. The obtained silicoaluminate was then heated with NaAlO₂ in an aqueous NaOH solution at 70-110 °C for 3-18 h and zeolite A was successfully prepared according to the X-ray diffraction measurements. By changing the hydrothermal temperature and time, ZA could reach 237.3 mmol/100 g in maximum cation exchange capacity. ZA impregnated with urea (ZA-U) at a mass ratio of more than 5:1 exhibited slow release of urea and the kinetics release mechanism of ZA-U was proposed. The plant growth test proved that the slow release of urea from ZA-U can promote the growth of maize seedling.

Mechanochemically Assisted Coal Fly Ash Conversion into Zeolite

Mechanically treated fly ash (FA) was utilised to provide Al and Si atoms for zeolite synthesis. A combination of mechanical fly ash activation and classical hydrothermal synthesis led to favourable dissolution of activated fly ash and improved crystallization of zeolites. The milling activation step induced structural changes in FA to promote its reactivity in alkaline solution. The conversion of milled FA into zeolite materials was finally completed in the second step, during hydrothermal synthesis. The effect of such factors as crystallization temperature, milling time, and solution conditioning were systematically studied. The physicochemical properties characterising the obtained zeolite materials were determined via particle size distribution (PSD), nitrogen adsorption-desorption, X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM), and powder X-ray diffraction (XRD). As a result, the best samples achieved a high degree of crystallinity and an extensive specific surface area of 292 m²/g, 87.4 m²/g, 41.9 m²/g for Na-X, Na-P1, and Na-A, respectively. The obtained results provide new and useful data for utilising fly ash resources and synthesising other practical zeolites through an innovative, mechanochemically assisted, and template-free approach.

Comparative lead adsorptions in synthetic wastewater by synthesized zeolite A of recycled industrial wastes from sugar factory and power plant

Increasing of industrializations causes of waste management problems, so use of industrial wastes for other purposes is an alternative option not only reducing industrial wastes but also providing benefit applications. Water contaminated by heavy metals is concerned because of their toxicity, so the water treatment is required. Sugar factory and power plant create big loads of wastes which are bagasse fly ash (BFA) and coal fly ash (CFA). Since BFA and CFA have good chemical properties, they are possible to apply as raw materials for synthesis of zeolite-type adsorbents. Thus, use of these industrial wastes for heavy metal adsorptions is a good idea to accomplish for the waste management and water quality. This study presented the modified method of zeolite A synthesis by BFA and CFA for lead removals, characteristic identifications of synthesized zeolite A adsorbents, their lead adsorption efficiencies, and their adsorption isotherm and kinetics were investigated. ZBG and ZCF were synthesized, and all analytic characterizations were determined that ZBG and ZCF corresponded to zeolite A standard (STD). ZBG and ZCF were demonstrated lead removal efficiencies of 100%. The highest negatively charged of ZBG and ZCF were found at pH of 5 matched to the highest lead removal efficiencies of both zeolite A adsorbents. Adsorption isotherms and kinetics of ZBG and ZCF were corresponded to Langmuir isotherm and pseudo-second-order kinetic model. Therefore, ZBG and ZCF are potential adsorbents for environmental applications along with reducing of industrial wastes.

Carbon dioxide emission control of a vermicompost process using fly ash

Composting and vermicomposting generate a valuable product rich in plant nutrients and at the same time, reduce environmental pollution. However, along with these processes and in relation to the metabolism of the microorganism and the worms present in the vermicomposting, CO₂ is emitted to the atmosphere, contributing to the greenhouse effect. Taking these issues into account, different masses of fly ash were used to study the control of the CO₂ of the gas coming from a vermicomposting process and to evaluate the possibility of using the adsorbent as fertilizer in the culture of lettuce Lactuca sativa. Along the vermicomposting process, an increase in the concentration of CO₂ emissions was observed, with a maximum level of emission at the day 20 of the process and an average of 770 mg/L in air. After the adsorption process, the CO₂ concentration was lower due to the effect of the fly ash that was able to trap the emitted gas. The percentage of CO₂ adsorption shows maximum values of 55.5, 58.1 and 63.8% with 0.5, 1 and 1.5 kg of fly ash, respectively. The CO₂ uptake capacities of the different loads of fly ash used were 3.39, 7.03 and 6.84 mmol CO₂/g sorbent with 0.5, 1 and 1.5 kg of fly ash, respectively. After five weeks of sowing L. sativa, it was observed that when no fly ash was used in the soil, the length of the stem was 10.2 cm. Then, the length of the stem was 22 cm, and 16 cm when 10% of fly ash was applied and not applied in the adsorption process, getting a significant correlation between the load of fly ash and the length of the stem. The r when fly ash was used in the adsorption process was 0.9817 and 0.9811 when no ash fly was used in the process.

CO2 adsorption performance of template free zeolite A and X synthesized from rice husk ash as silicon source

In this work, zeolite NaA (RA) and NaX (RX) have been successfully synthesized using rice husk ash and it is a low cost synthesis process and it does not produce environmental hazards. Sodium silicate (SS) is extracted from rice husk ash which is an alternative silica source for zeolite synthesis. The zeolites are prepared by using a SS silica source extracted from the rice husk ash, and it has been used as an adsorbent for the CO₂ adsorption process which may help in controlling the global warming problems. The zeolites are synthesized by a hydrothermal method without using any organic templating agent. FESEM and TEM micrographs revealed that the synthesized zeolites RA and RX have “Ice cube” and octahedral morphology respectively. From the N₂ sorption studies, the BET surface area of the synthesized zeolites have been found and are 106.25 m² g⁻¹ and 512.79 m² g⁻¹ respectively. The maximum CO₂ adsorption capacities of zeolite RA and RX are 2.22 and 2.45 mmol g⁻¹, respectively at a temperature of 297.15 K. The recorded data are fitted by using non-linear adsorption isotherm models of Langmuir, Freundlich and Toth isotherm models. The fitted isotherm models are observed to be a type I adsorption isotherm according to the IUPAC classification criterion.

In this work, zeolite NaA (RA) and NaX (RX) have been successfully synthesized using rice husk ash as source and it is a low cost synthesis process and it does not produce any environmental hazards.

Synthesis and photocatalytic degradation of rhodamine B using ternary zeolite/WO3/Fe3O4composite

Demand for freshwater increases day by day as impurity increases due to the industrial, domestic and municipal waste in the water. Inappropriate disposal of coal fly ash (CFA) is not eco-friendly, therefore the need is to convert it into some beneficial material like zeolite. Zeolite-based composites with metal oxides show high cation interchange capacity, fast adsorption, and high efficiency for the removal of wastewater pollutants. In this research work, metal oxide along with zeolite (derived for CFA) was prepared. Metal oxide (WO₃) and magnetite (Fe₃O₄) based zeolite composite was used adsorption enhanced photocatalytic degradation of rhodamine B dye. Ternary composite (zeolite/WO₃/Fe₃O₄) was characterized using a scanning electron microscope, x-ray diffraction, Fourier transform infrared spectroscopy. The bandgap energy of composite was estimated using Tauc plot method from the data obtained after UV-visible spectroscopy. The behavior of composite under acidic and basic conditions was analyzed using pH_pzcof the composite. Influencing parameters like pH, dye concentration, contact time, and catalyst dosage was optimized under ultraviolet irradiations (254 nm). The results show that maximum degradation was achieved with zeolite/WO₃/Fe₃O₄composite under optimized conditions of pH = 7, catalyst dosage = 10 mg/100 ml, RhB concentration 10 ppm, and time 60 min. The first-order kinetic model was best fitted to the experimental data. RSM was used as a statistical tool to analyze the data.

Synthesis of Single-Phase Zeolite A by Coal Gasification Fine Slag from Ningdong and Its Application as a High-Efficiency Adsorbent for Cu2+ and Pb2+ in Simulated Waste Water

Coal gasification is a new direction for the clean utilization of coal, but it also brings huge environmental pressure on solid waste. In this paper, the high-crystallinity single-phase zeolite A was prepared by solid-phase alkali fusion synthesis from coal gasification fine slag (CGFS), without template agent, with low water consumption, and with low cost, and it was used to remove heavy metals such as Pb2+ and Cu2+ in simulated waste water. The main factors affecting the solid-phase and green synthesis methods were analyzed, and the optimum conditions for solid-phase synthesis of high-crystallinity single-phase zeolite A were determined as follows: NaOH/CGFS = 1.2; solid-phase alkali fusion temperature 823 K, solid-phase alkali fusion 90 min, liquid–solid ratio 4.5, and 353 K hydrothermal reaction for 12 h. The relative crystallinity, specific surface area, and ion-exchange capacity of single-phase zeolites A are 93.1%, 61.09 m2/g, and 268.4 mmol/100 g. The removal rates of Pb2+ and Cu2+ can reach more than 99%, especially for the removal efficiency of Pb2+, which is common in simulated waste water. This is an effective method with important application prospects, and it formed an effective way to recycle solid waste of coal chemical industry.

Synthesis of Zeolites from Greek Fly Ash and Assessment of Their Copper Removal Capacity

The objective of this study was to synthesize zeolites through fusion of lignite fly ash and NaOH or KOH pellets at 600 °C and assess their removal efficiency in terms of decontamination of solutions containing Cu(II) ions. The removal efficiency of the produced zeolites was tested in batch kinetic experiments using different zeolites and Cu(II) ion concentrations. Experimental data revealed that zeolites synthesized with the use of NaOH exhibited higher removal efficiency compared with those synthesized with the use of KOH. Kinetic data showed that the pseudo-second-order equations described well the removal process. Copper removal was mainly accomplished through the concerted action of chemisorption and intraparticle diffusion. Analytical techniques involving XRF, XRD, FTIR, SEM/EDS and XPS were used for the characterization and morphology analysis of the produced zeolites. SEM/EDS confirmed the presence of copper on the zeolite surface. XPS spectra of Cu2p at 934.3 eV proved the presence of Cu(II) oxidation state, confirming the possible formation of CuO and/or Cu-Cl.

Dechlorination of fly ash by hydrolysate of municipal solid waste leachate

Municipal solid waste incineration fly ash (referred to as the fly ash) presents an important environmental problem in China today, but strategies for its treatment have yet to be widely studied and implemented. The currently available methods for the dechlorination of fly ash are not sufficient, given the amounts of fly ash produced each year. To increase the reuse fraction of fly ash as raw material for cement production, we propose an improved dechlorination method. Specifically, fly ash was leached with the hydrolysate of municipal solid waste leachate (HMSWL) to remove the water-insoluble chlorine. Three-step HMSWL leaching removed 94.3% of the total chlorine in fly ash, much more than the 82.7% that was removed through three-step ultrapure water (UW) leaching. X-ray diffraction indicated that three-step UW leaching could remove Cl mainly in the forms of KCl, NaCl, CaClOH and AlOCl, whereas three-step HMSWL leaching could further remove more water-insoluble Cl in the forms of AlOCl. In addition, the experimental results further suggested that the low pH of HMSWL (4.9) contributed little to the water-insoluble Cl removal, whereas the displacement of organic acid radicals (especially by the butyrate radical) was the major cause of water-insoluble Cl removal. Therefore, HMSWL rich in butyrate radical could be an ideal water substitute for fly ash dechlorination.

Microwave-assisted synthesis of coal fly ash-based zeolites for removal of ammonium from urine

Zeolites synthesized from biomass waste materials offer a great opportunity in the sustainable utilization of the waste.