In this study, a mineral-based coated urea was fabricated in a rotary pan coater using a mixture of gypsum/sulfur/zeolite (G25S25Z50) as an effective and low-cost coating material. The effects of different coating compositions on the dissolution rate of urea and the crushing strength and morphology of the coated urea were investigated. A 25:25:50 (wt %) mixture of gypsum/sulfur/zeolite (G25S25Z50) increased the coating effectiveness to 34.1% with the highest crushing strength (31.06 N). The effectiveness of coated urea was further improved to 46.6% with the addition of a microcrystalline wax (3%) as a sealant. Furthermore, the release mechanisms of various urea fertilizers were determined by fitting the release profiles with six mathematical models, namely, the zeroth-order, first-order, second-order, Higuchi, Ritger & Peppas, and Kopcha models. The results showed that the release mechanism of the uncoated urea and all other coated urea followed the Ritger & Peppas model, suggesting the diffusional release from nonswellable delivery systems. In addition, due to the increased mass-transfer resistance, the kinetic constant was decreased from 0.2233 for uncoated urea to 0.1338 for G25S25Z50-coated urea and was further decreased to 0.0985 when 3% Witcovar 146 sealant was applied.
Fly ash (PFA) is a complex material produced after combustion in coal-fired power plants. About half of this fly ash is disposed as solid wastes. A possible alternative to disposal of the fly ash is the synthesis of zeolite. Zeolite Boggsite (Na37Ca74Al185Si775O192 7H2O) was synthesized from fly ash by hydrothermal treatment with NaOH solutions as identified by x-ray diffraction. The zeolite type and degree of crystallization were found to be dependent on the reaction conditions and mineralogy of the raw material, particularly in terms of the relative concentrations of SiO2 and Al2O3.
Ordered microporous NaY zeolite and mesoporous copper oxide are high performance material as catalysts and adsorbents. The copper oxide-NaY zeolite modification in combination of their physicochemical properties could provide excellent opportunities for the creation of new gas adsorbents. In this study, modified NaY zeolite properties and methane adsorptive characteristics were investigated by dispersing copper oxide onto the NaY zeolite structure using the thermal dispersion method. The structures of the copper oxide modified zeolites were characterized by powder X-ray diffraction and Micromeritics ASAP 2000, while the methane adsorption characteristics were analyzed using a thermogravimetric analyzer. The results revealed that types of copper oxide, copper oxide loading concentration, calcination temperature and calcination time greatly affected the modified zeolite structure and gas methane adsorption characteristics.
The effects of zeolite and zinc foliar applications on the biochemical characteristics of canola cultivars under different moisture regimes were investigated in a study conducted during the 2010 and 2011 growing seasons. The study was completed using a factorial split-plot experiment based on randomized complete block design (RCBD) with three replications at the Seed and Plant Improvement Institute (SPII), Karaj, Iran. The treatments were: irrigation (I): complete (I1) and restricted (I2); zeolite (Z): 0 (Z1) and 15 ton ha-1 (Z2) and Zn: 0, 0.1 and 0.2% concentrations of zinc sulfate (Zn1, Zn2, and Zn3) at the pod formation stage. These treatments were applied during the pod formation stage to the Licord, RGS003 and Opera cultivars. This study showed that although applying Z and Zn had positive effects on the quality of canola, the highest performance and the best results were obtained using a combination of Z and Zn. The combined application of Z and Zn decreased the proline and carbohydrate contents to 44.35 and 34.42%, respectively. Therefore, with the low cost of natural Z and moderate Zn intake, these treatments can be used to enhance the performance of canola, especially in regions frequently subjected to water stress.
Nanocrystalline aluminosilicate F-type zeolite (K-F, EDI-type structure) was synthesized in an organic template-free system
using rice husk ash (RHA) silica source and microwave energy. The morphology, crystallite size, chemical composition,
crystallographic and basicity properties of the nanocrystals were studied by using various characterization techniques.
The results showed that fully crystalline K-F zeolite (Si/Al ratio = 1.26) with flattened cuboid-like shaped could be
obtained within 2 min of crystallization which was considerably very fast. In addition, K-F zeolite nanocrystals was also
tested as a solid base catalyst in the microwave-enhanced Aldol condensation reaction of heptanal with benzaldehyde
and the six catalytic parameters were studied and optimized. The nanosized K-F zeolite crystals showed good catalytic
performance in the studied reaction with 77.1% heptanal conversion and 69.5% jasminaldehyde selectivity under optimum
reaction condition. The nanocatalyst was reusable and no significant loss in its catalytic reactivity was observed even
after five consecutive reaction cycles.
Bionanocomposite films based on regenerated cellulose (RC) and incorporated with zeolite at different concentrations were fabricated by dissolving cellulose in 1-ethyl-3-methylimidazolium chloride (EMIMCl) ionic liquid using a simple green method. The interactions between the zeolite and the cellulose matrix were confirmed by Fourier transform infrared spectra. Mechanical properties of the nanocomposite films significantly improved as compared with the pure regenerated cellulose film, without the loss of extensibility. Zeolite incorporation enhanced the thermal stability and char yield of the nanocomposites. The scanning electron microscopy and transmission electron microscopy showed that zeolite was uniformly dispersed in the regenerated cellulose matrix. In vitro cytotoxicity test demonstrated that both RC and RC/zeolite nanocomposite films are cytocompatible. These results indicate that the prepared nanocomposites have potential applications in biodegradable packaging, membranes and biomedical areas.
This study focused on improving the producer gas quality using radio frequency (RF) tar thermocatalytic treatment reactor. The producer gas containing tar, particles and water was directly passed at a particular flow rate into the RF reactor at various temperatures for catalytic and thermal treatments. Thermal treatment generates higher heating value of 5.76 MJ Nm(-3) at 1200°C. Catalytic treatments using both dolomite and Y-zeolite provide high tar and particles conversion efficiencies of about 97% on average. The result also showed that light poly-aromatic hydrocarbons especially naphthalene and aromatic compounds particularly benzene and toluene were still found even at higher reaction temperatures. Low energy intensive RF tar thermocatalytic treatment was found to be effective for upgrading the producer gas quality to meet the end user requirements and increasing its energy content.
Zeolite Linde Type L (LTL) crystals with different length, diameter and particle size (nanosized LTL, rod LTL, cylinder LTL and needle LTL) were synthesized, characterized and were used as sorbent in the micro-solid phase extraction of ochratoxin A (OTA) before the high performance liquid chromatography detection. Under the optimized conditions, the detection limits of OTA for coffee and cereal were 0.09 ng g(-1) and 0.03 ng g(-1), respectively, while the quantification limits were 0.28 ng g(-1) and 0.08 ng g(-1), respectively. The recoveries of OTA of coffee and cereal spiked at 0.5, 10 and 25 ng g(-1) ranged from 91.7 to 101.0%. The proposed method was applied to forty-five samples of coffee and cereal. The presence of OTA was found in twenty-five samples, ranging from 0.28 to 9.33 ng g(-1).
A new heterogeneous catalyst for sonocatalytic degradation of amaranth dye in water was synthesized by introducing titania into the pores of zeolite (NaY) through ion exchange method while Fe (III) was immobilized on the encapsulated titanium via impregnation method. XRD results could not detect any peaks for titanium oxide or Fe(2)O(3) due to its low loading. The UV-vis analysis proved a blue shift toward shorter wavelength after the loading of Ti into NaY while a red shift was detected after the loading of Fe into the encapsulated titanium. Different reaction variables such as TiO(2) content, amount of Fe, pH values, amount of hydrogen peroxide, catalyst loading and the initial dye concentration were studied to estimate their effect on the decolorization efficiency of amaranth. The maximum decolorization efficiency achieved was 97.5% at a solution pH of 2.5, catalyst dosage of 2 g/L, 20 mmol/100 mL of H(2)O(2) and initial dye concentration of 10 mg/L. The new heterogeneous catalyst Fe/Ti-NaY was a promising catalyst for this reaction and showed minimum Fe leaching at the end of the reaction.
The catalytic cracking of waste cooking palm oil to biofuel was studied over different types of nano-crystalline zeolite catalysts in a fixed bed reactor. The effect of reaction temperature (400-500 °C), catalyst-to-oil ratio (6-14) and catalyst pore size of different nanocrystalline zeolites (0.54-0.80 nm) were studied over the conversion of waste cooking palm oil, yields of Organic Liquid Product (OLP) and gasoline fraction in the OLP following central composite design (CCD). The response surface methodology was used to determine the optimum value of the operating variables for maximum conversion as well as maximum yield of OLP and gasoline fraction, respectively. The optimum reaction temperature of 458 °C with oil/catalyst ratio=6 over the nanocrystalline zeolite Y with pore size of 0.67 nm gave 86.4 wt% oil conversion, 46.5 wt% OLP yield and 33.5 wt% gasoline fraction yield, respectively. The experimental results were in agreement with the simulated values within an experimental error of less than 5%.
The removal of ammonium from aqueous solutions using zeolite NaY prepared from a local agricultural waste, rice husk ash waste was investigated and a naturally occurring zeolite mordenite in powdered and granulated forms was used as comparison. Zeolite NaY and mordenite were well characterized by powder X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis and the total cation exchange capacity (CEC). CEC of the zeolites were measured as 3.15, 1.46 and 1.34 meq g(-1) for zeolite Y, powdered mordenite and granular mordenite, respectively. Adsorption kinetics and equilibrium data for the removal of NH(4)(+) ions were examined by fitting the experimental data to various models. Kinetic studies showed that the adsorption followed a pseudo-second-order reaction. The equilibrium pattern fits well with the Langmuir isotherm compared to the other isotherms. The monolayer adsorption capacity for zeolite Y (42.37 mg/g) was found to be higher than that powdered mordenite (15.13 mg/g) and granular mordenite (14.56 mg/g). Thus, it can be concluded that the low cost and economical rice husk ash-synthesized zeolite NaY could be a better sorbent for ammonium removal due to its rapid adsorption rate and higher adsorption capacity compared to natural mordenite.
The synthesized zeolite NaY from rice husk ash (RHA) and the commercial zeolite NaY both modified with surfactants in amounts equal to 50%, 100% and 200% of their external cation exchange capacity (ECEC) were used to remove chromate and arsenate anions from aqueous solutions. While the unmodified zeolite Y had little or no affinity for the Cr(VI) and As(V) anionic species, the surfactant-modified zeolite Y (SMZY) showed significant ability to remove of these anions from the aqueous solutions. The highest chromates and arsenates adsorption efficiency was observed from solutions of pH values 3 and 8, respectively because of the dominance of the univalent species of both anions. The adsorption equilibrium data were best fitted with the Langmuir isotherm model with the highest removal capacities observed for the SMZY initially prepared considering the hexadecyltrimethyl ammonium (HDTMA) amount equal to the 100% of the ECEC of zeolite Y. Synthesized SMZY remove Cr(VI) and As(V) more than the corresponding commercial one due to its lower silica to alumina ratio. Thus, the HDTMA-covered modified zeolite Y synthesized using RHA can be used to remove Cr(VI) and As(V) from water.
White rice husk ash (RHA), an agriculture waste containing crystalline tridymite and alpha-cristobalite, was used as a silica source for zeolite Beta synthesis. The crystallization of zeolite Beta from RHA at 150 degrees C in the presence of tetraethylammonium hydroxide was monitored by XRD, FTIR and (29)Si MAS NMR techniques. It was found that zeolite Beta started to form after 12h and the complete crystallization of zeolite Beta phase was achieved after 2d. XRD, (29)Si MAS NMR and solid yield studies indicate that the transformation mechanism of silica present in RHA to zeolite Beta involves dissolution of the ash, formation of an amorphous aluminosilicate after 6h of crystallization, followed by dissolution in the mother liquor and final transformation to pure zeolite Beta crystals.
Fenton oxidation, an advanced oxidation process, is an efficient method for the treatment of recalcitrant wastewaters. Unfortunately, it utilizes H2O2 and iron-based homogeneous catalysts, which lead to the formation of high volumes of sludge and secondary pollutants. To overcome these problems, an alternate option is the usage of heterogeneous catalyst. In this study, a heterogeneous catalyst was developed to provide an alternative solution for homogeneous Fenton oxidation. Iron Zeolite Socony Mobile-5 (Fe-ZSM-5) was synthesized using a new two-step process. Next, the catalyst was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis and tested against a model wastewater containing the azo dye Acid Blue 113. Results showed that the loading of iron particles reduced the surface area of the catalyst from 293.59 to 243.93 m2/g; meanwhile, the average particle size of the loaded material was 12.29 nm. Furthermore, efficiency of the developed catalyst was evaluated by performing heterogeneous Fenton oxidation. Taguchi method was coupled with principal component analysis in order to assess and optimize mineralization efficiency. Experimental results showed that under optimized conditions, over 99.7% degradation and 77% mineralization was obtained, with a 90% reduction in the consumption of the developed catalyst. Furthermore, the developed catalyst was stable and reusable, with less than 2% leaching observed under optimized conditions. Thus, the present study proved that newly developed catalyst has enhanced the oxidation process and reduced the chemicals consumption.
The availability of paddy husk from rice processing plants remains high owing to increase in the worldwide rice consumption. Increasing demand for chicken products leads to poultry wastes production. Co-composting of the aforementioned wastes could solve the indiscriminate disposal of these wastes. Thus, co-composting of paddy husk and chicken slurry with clinoptilolite zeolite and urea as additive was carried out. Clinoptilolite zeolite was used to enhance ammonium and nitrate retention in the compost. Temperature of the compost was monitored three times daily for 55 days. Cation exchange capacity, organic matter, ash, humic acids, pH, total C, N, C/N ratio; total P, exchangeable Ca, Mg, K, NH4+, NO3-, and heavy metals contents were determined using standard procedures. pH, total N, humic acids, ash, NH4+, NO3-, P, Ca, Mg, and K contents increased but the salinity, heavy metals contents, and microbial population were low after the co-composting process. Zea mays L. (test crop) seed germination rate in distilled water and the compost were not significantly different. Growth of Spinach oleracea (test crop) on a peat-based growing medium and the compost was also not significantly different. These findings were possible because the clinoptilolite zeolite used in co-composting reduced accumulation of heavy metals that may have damage effects on the test crops. Mature compost with good agronomic properties can be produced by co-composting chicken slurry and paddy husk using clinoptilolite zeolite and urea as additives.
Improper use of urea may cause environmental pollution through NH3 volatilization and NO3 (-) leaching from urea. Clinoptilolite zeolite and compost could be used to control N loss from urea by controlling NH4 (+) and NO3 (-) release from urea. Soil incubation and leaching experiments were conducted to determine the effects of clinoptilolite zeolite and compost on controlling NH4 (+) and NO3 (-) losses from urea. Bekenu Series soil (Typic Paleudults) was incubated for 30, 60, and 90 days. A soil leaching experiment was conducted for 30 days. Urea amended with clinoptilolite zeolite and compost significantly reduced NH4 (+) and NO3 (-) release from urea (soil incubation study) compared with urea alone, thus reducing leaching of these ions. Ammonium and NO3 (-) leaching losses during the 30 days of the leaching experiment were highest in urea alone compared with urea with clinoptilolite zeolite and compost treatments. At 30 days of the leaching experiment, NH4 (+) retention in soil with urea amended with clinoptilolite zeolite and compost was better than that with urea alone. These observations were because of the high pH, CEC, and other chemical properties of clinoptilolite zeolite and compost. Urea can be amended with clinoptilolite zeolite and compost to improve NH4 (+) and NO3 (-) release from urea.
Cylinder-shaped NaY zeolite was used as an adsorbent for eradicating both heavy metal ions (Cu2+, Zn2+, Ni2+, and Co2+) and proteins from the waste streams. As a pseudo-metal ion affinity adsorbent, NaY zeolite was used in the capture of heavy metal ions in the first stage. The amount (molar basis) of metal ions adsorbed onto NaY zeolite decreased in the order of Cu2+ > Zn2+ > Co2+ > Ni2+. Bovine serum albumin (BSA) was utilized as a model of proteins used in the waste adsorption process by NaY zeolite. The adsorption capacities of NaY zeolite and Cu/NaY zeolite for BSA were 14.90 mg BSA/g zeolite and 84.61 mg BSA/g zeolite, respectively. Moreover, Cu/NaY zeolite was highly stable in the solutions made of 2 M NaCl, 500 mM imidazole or 125 mM EDTA solutions. These conditions indicated that the minimal probability of secondary contamination caused by metal ions and soluble proteins in the waste stream. This study demonstrates the potential of Cu/NaY zeolite complex as an efficient pseudo-metal chelate adsorbent that could remove metal ions and water-soluble proteins from wastewater concurrently.
Efficient management of P fertilizers ensures good yield of crops and adequate food supply. In the acid soil of the tropics, soluble P is fixed by Al and Fe. Exploitation of the high CEC and pH of Clinoptilolite zeolite (CZ) could mitigate low soil pH and P fixation in acid soils. This study was undertaken to determine the effects of amending a weathered acid soil with CZ on: (i) soil P availability and other related soil chemical properties, and (ii) nutrient concentration, nutrient uptake, above-ground biomass, agronomic efficiency, and yield of Zea mays L. on a tropical acidic soil. Triple superphosphate (TSP), Egypt Rock phosphate (ERP), and Christmas Island Rock phosphate (CIRP) were used as P sources. The treatments evaluated were: (i) soil alone, (ii) 100% recommended fertilizer rate (NPK), and (iii) 75% fertilizer rate + Clinoptilolite zeolite. Selected soil chemical properties and P availability were determined before and after field trials. Zea mays L. above-ground biomass, nutrient concentration, nutrient uptake, agronomic efficiency, and fresh cob yield were also determined. Results revealed that the effects of treatments with and without CZ treatments on soil pH, P fractions, soil acidity, dry matter production, yield of maize, nutrient uptake, and agronomic efficiency were similar. Hence, suggesting CZ inclusion in the fertilization program of Zea mays L is beneficial in terms of reducing excessive or unbalanced use of chemical fertilizers due to reduction of fertilizers usage by 25%.
Heavy metal contamination in aqueous system has attracted global attention due to the toxicity and carcinogenicity effects towards living bodies. Among available removal techniques, adsorptive removal by nanosized materials such as metal oxide, metal organic frameworks, zeolite and carbon-based materials has attracted much attention due to the large active surface area, large number of functional groups, high chemical and thermal stability which led to outstanding adsorption performance. However, the usage of nanosized materials is restricted by the difficulty in separating the spent adsorbent from aqueous solution. The shift towards the use of adsorptive composite membrane for heavy metal ions removal has attracted much attention due to the synergistic properties of adsorption and filtration approaches in a same chamber. Thus, this review critically discusses the development of nanoadsorbents and adsorptive nanocomposite membranes for heavy metal removal over the last decade. The adsorption mechanism of heavy metal ions by the advanced nanoadsorbents is also discussed using kinetic and isotherm models. The challenges and future prospect of adsorptive membrane technology for heavy metal removal is presented at the end of this review.
In all-ceramic systems, a high incidence of veneer chip-off has been reported in clinical studies. Coefficient of thermal expansion (CTE) behaviour is one of the factors that may increase residual stress in the interface and influence the veneer/core bond strength. Therefore, this study aimed to evaluate the effect of sodalite zeolite-infiltration on the CTE behaviour and bond strength of different all-ceramic prostheses. The case-study groups were synthesized sodalite zeolite-infiltrated alumina (IA-SOD) and synthesized sodalite zeolite-infiltrated zirconia-toughened alumina (ZTA) (IZ-SOD), while the control groups were glass-infiltrated alumina (IA-glass) and glass-infiltrated ZTA (IZ-glass). Forty cylindrical-shaped samples measuring 5 mm in diameter and 10 mm in height were tested for CTE using a thermo-mechanical analyser machine, and forty disc-shaped ceramic samples measuring 12 mm in diameter and 1.2 ± 0.2 mm in thickness were prepared using specially designed stainless steel split mould and veneered by cylinder-shaped (2 mm high × 2 mm diameter) low-fusing porcelain (Vita VM7). The veneer/core samples were sintered and tested for shear bond strength using a high precision universal testing machine. Scanning electron microscope, stereo microscope, atomic force microscope, and energy-dispersive X-ray spectroscopy were used to investigate the structural characteristics of samples at the fracture surface. The collected data were analyzed with a one-way ANOVA and Tukey HSD test (α=.05). IZ-SOD revealed highest CTE and shear bond strength values, while the IA-glass revealed the lowest values than the other groups. There was no significant difference in CTE and bond strength among IZ-SOD, IA-SOD and IZ-glass samples (p>0.05). The experimental SOD zeolite-infiltrated samples revealed higher CTE mismatch and bond strength along with a more favourable mode of failure than did the commercial glass-infiltrated samples. Sandblast technique is considered as effective conditioning procedure for enhancing the surface roughness of SOD zeolite-infiltrated frameworks which subsequently improving the bond strength.