Influence of different natural zeolite concentrations on the anaerobic digestion of piggery waste

The effect of different natural zeolite concentrations on the anaerobic digestion of piggery waste was studied. Natural zeolite doses in the range 0.2-10 g/l of wastewater were used in batch experiments, which were carried out at temperatures between 27 degrees C and 30 degrees C. Total chemical oxygen demand (COD), total and volatile solids, ammonia and organic nitrogen, pH, total volatile fatty acids (TVFA), alkalinity (Alk) and accumulative methane production were determined during 30 days of digestion. The anaerobic digestion process was favored by the addition of natural zeolite at doses between 2 and 4 g/l and increasingly inhibited at doses beyond 6 g/l. A first-order kinetic model of COD removal was used to determine the apparent kinetic constants of the process. The kinetic constant values increased with the zeolite amount up to a concentration of 4 g/l. The values of the maximum accumulative methane production (Gm) increased until zeolite concentrations of 2-4 g/l. The addition of zeolite reduced the values of the TVFA/ Alk ratio while increasing the pH values, and these facts could contribute to the process failure at zeolite doses of 10 g/l.     

The effects of natural zeolite on salinity level of poultry litter compost

The aim of this study was to investigate the salinity uptake by natural zeolite when used as an ingredient during the composting process. The amounts of 5% and 10% of natural zeolite were applied to poultry litter as volume and compared with the compost made with no amendment. The results clearly showed that the salinity level of poultry litter was too high. It was found that the salinity level in the end compost decreases with increasing the amount of natural zeolite used. Salinity uptake efficiencies were 66.64% and 88.92% for end product containing 5% and 10% natural zeolite, respectively. Significantly, the addition of natural zeolite to poultry litter compost was found to have a beneficial effect on the characteristics of the end product.     

Assessment of a UASB reactor with high ammonia concentrations: Effect of zeolite addition on process performance

The UASB process for wastewater treatment has been extensively studied, but the use of zeolite to improve UASB reactor performance has rarely been explored. In this study, a UASB reactor modified with natural zeolite operating at high nitrogen concentrations (0.5, 0.7 and 1 g/L) was evaluated. Two laboratory bioreactors, one with zeolite and one without, were operated at ambient temperatures ranging between 18 °C and 21 °C. The experimental phase had a start-up period of 21 days. In the reactor with zeolite, the pH was found to be between 7.9 and 9.1, with a COD removal efficiency of about 60% after 80 days of operation at ammonia concentrations of between 0.229 and 0.429 g/L in the effluent. In the reactor without zeolite, the pH was between 8.3 and 9.3, and the COD removal efficiency was about 40% at ammonia concentrations between 0.244 and 0.535 g/L in the effluent. The addition of zeolite also decreased the volatile suspended solids (VSS) concentration in the effluent, generating a biomass with larger granules and higher settling rates as compared to a UASB reactor without zeolite. Taking the lower ammonia concentration, the higher COD removal and the improved granulation into account, it can be concluded that natural zeolite positively influenced the behavior and performance of the UASB reactor operating with high nitrogen concentrations.     

Effect of Si/Al ratio on tetralin adsorption on Y zeolite: a DFT study

Probing the adsorption of tetralin on zeolite is of prime scientific and industrial importance with the aim to upgrade the industrial process of tetralin cracking. In this work, the effect of Si/Al ratio ranging from 12 to 39 on tetralin adsorption property on Y zeolite is studied by DFT calculations. Tetralin adsorption on Y zeolite corresponds to a π-stacking adsorption mechanism between double bonds of aromatic ring and Brønsted acid sites. Therefore, the number of Brønsted acid sites influences the adsorption properties. Lower Si/Al ratio with more Brønsted acid sites interacting with the aromatic ring of tetralin leads to a higher adsorption energy. Furthermore, the charge and frontier molecular orbital analysis are also performed to understand the influence of Si/Al ratio on adsorption performance. Y zeolite with lower Si/Al ratio shows larger charge difference values and lower HOMO–LUMO gap, which directly manifests the stronger adsorption ability of tetralin and indicates bigger possibility of reacting.     

Molecular Dynamics Studies of Light Hydrocarbons Diffusion in Zeolites

Molecular dynamics simulation techniques have been used to study the diffusion of methane, ethane, propane and i-butane into the zeolite ZSM-5. From the trajectories, the mean-square displacements were obtained and the diffusion coefficients determined using Einstein's diffusion equation. The results, when compared to the available experimental data, indicate that the simulations can provide a realistic representation of the microscopic process of diffusion into the zeolite pores. This revised version was published online in June 2006 with corrections to the Cover Date.     

乙醇催化脱水制乙烯反应条件及飞温现象

以HZSM-5分子筛为乙醇脱水催化剂,考察了催化剂的硅铝摩尔比和反应工艺条件对乙醇转化率及生成乙烯选择性的影响,分析了反应初期的飞温现象,用X射线衍射（XRD）、环境扫描电镜（SEM）和热分析（TG-DTA）对其催化剂进行了表征。结果表明：硅铝摩尔比为50∶1的HZSM-5催化乙醇脱水制乙烯反应在温度300℃、液体质量空速7h-1时,乙醇转化率大于99.8%,乙烯选择性达99.1%。HZSM-5催化乙醇脱水反应初期的飞温过程生成的聚合物堵塞和覆盖部分催化剂孔道,导致催化剂活性下降和乙烯选择性显著降低,适当降低进料温度可有效控制飞温现象发生。     

Investigation of mircroorganisms colonising activated zeolites during anaerobic biogas production from grass silage

The colonisation of activated zeolites (i.e. clinoptilolites) as carriers for microorganisms involved in the biogas process was investigated. Zeolite particle sizes of 1.0-2.5 mm were introduced to anaerobic laboratory batch-cultures and to continuously operated bioreactors during biogas production from grass silage. Incubation over 5-84 days led to the colonisation of zeolite surfaces in small batch-cultures (500 ml) and even in larger scaled and flow-through disturbed bioreactors (28 l). Morphological insights were obtained by using scanning electron microscopy (SEM). Single strand conformation polymorphism (SSCP) analysis based on amplification of bacterial and archaeal 16S rRNA fragments demonstrated structurally distinct populations preferring zeolite as operational environment. via sequence analysis conspicuous bands from SSCP patterns were identified. Populations immobilised on zeolite (e.g. Ruminofilibacter xylanolyticum) showed pronounced hydrolytic enzyme activity (xylanase) shortly after re-incubation in sterilised sludge on model substrate. In addition, the presence of methanogenic archaea on zeolite particles was demonstrated.     

Fabrication of silver ion exchanged zeolite using scoria and its antibacterial activity

In this study, we examined the antibacterial activity of silver ion exchanged zeolite synthesized from Cheju Scoria. We synthesized zeolite in various NaOH concentrations, but zeolite synthesized in 4 M NaOH was most similar to type A zeolite. Using the synthesized zeolite, we prepared a silver ion exchanged zeolite for studies of antibacterial activity. Antibacterial tests using agar cultures of Escherichia coli (E. coli), with silver ion exchanged zeolite showed a zone of inhibition colonies bacteria did not grow near silver ion exchanged zeolite. Furthermore, spectrophotometry demonstrated a significantly low absorbance of E. coli culture mediums when silver ion exchanged zeolite was included indicating that E. coli propagation was prevented. Through results of these experiments, we conclude that synthesized products with sodalite crystal can be synthesized from Scoria, and these are suitable to produce silver ion exchanged zeolite with antibacterial activity.     

Anaerobic digestion of swine manure under natural zeolite addition: VFA evolution, cation variation, and related microbial diversity

Batch experiments were carried out on anaerobic digestion of swine manure under 10 % of total solids and 60 g/L of zeolite addition at 35 °C. Four distinctive volatile fatty acid (VFAs) evolution stages were observed during the anaerobic process, i.e., VFA accumulation, acetic acid (HAc) and butyric acid (HBu) utilization, propionic acid (HPr) and valeric acid (HVa) degradation, and VFA depletion. Large decreases in HAc/HBu and HPr/HVa occurred respectively at the first and second biogas peaks. Biogas yield increased by 20 % after zeolite addition, about 356 mL/g VS_added with accelerated soluble chemical oxygen demand degradation and VFA (especially HPr and HBu) consumption in addition to a shortened lag phase between the two biogas peaks. Compared with Ca²⁺ and Mg²⁺ (100–300 mg/L) released from zeolite, simultaneous K⁺ and NH₄ ⁺ (580–600 mg/L) adsorptions onto zeolite particles contributed more to the enhanced biogasification, resulting in alleviated inhibition effects of ammonium on acidogenesis and methanogenesis, respectively. All the identified anaerobes could be grouped into Bacteroidetes and Firmicutes, and zeolite addition had no significant influence on the microbial biodiversity in this study.     

Protection by clinoptilolite or zeolite NaA against cadmium-induced anemia in growing swine

Weanling Landrace X Yorkshire swine were fed a basal diet or a diet containing 3% clinoptilolite (a natural zeolite) with or without 150 ppm CdCl2 or 3% zeolite NaA (a synthetic zeolite) with or without 150 ppm CdCl2 for 31 days. Hematocrit and hemoglobin were depressed significantly in animals fed Cd in the absence of zeolites, but not in their presence. Liver Cd concentration was increased dramatically by added dietary Cd but was significantly lower in animals fed clinoptilolite with Cd than in those fed Cd alone (11.4 vs 16.5 ppm). Liver Fe and Zn were decreased by dietary Cd; liver Fe was not affected significantly by clinoptilolite or zeolite NaA, but liver Zn was increased by zeolite NaA. Kidney dry matter, Zn, and Cd concentrations were increased by dietary Cd; neither clinoptilolite nor zeolite NaA affected kidney Cd concentration. Zeolite NaA increased kidney dry matter both in the presence and in the absence of dietary Cd. Plasma urea-N, K, Na, and Mg were unaffected by Cd or by either zeolite. The data illustrate the different effects of dietary clinoptilolite compared with zeolite NaA on blood plasma, liver, and kidney concentrations of minerals and provide evidence that both zeolites offer some protection against Cd-induced Fe-deficiency anemia; the magnitude of this protection and the effects of each zeolite on tissue concentrations of Cd and other materials need further quantification.     

Zeolite (clinoptilolite) as feed additive to reduce manure mineral content

Clinoptilolite (a species of zeolite) as grower hog feed additive can potentially improve nutrient ingestion and lower manure nutrient levels. A first objective was to establish the optimal particle size of the zeolite powder, as a fine size increases the adsorption surface while a coarse size can facilitate handling. The second objective tested the effect of feeding zeolite on manure nutrient levels. For the first objective, three zeolite powders (250-500 microm; 50-250 microm, and 50-500 microm) were exposed to an NH(4)(+) solution under a pH of either 7.0 or 2.0. The resulting solutions were tested for cation exchange. A commercial zeolite was also tested for the pH of 2.0 to evaluate zeolite stability. At 0%, 5% and 10% humidity, the same three particle size powders were subjected to shear tests to determine the zeolite's angle of friction. For the second objective using metabolic cages, female hogs were subjected to one of four rations (a control and three with zeolite) while collecting and analyzing their manures. For the first objective, the coarse particle zeolite performed best, adsorbing 158 and 123 Cmol(+)/kg of NH(4)(+) under neutral and acid pH, respectively, and releasing an equivalent amount of minerals only under neutral pH. The commercial zeolite with less clinoptilolite released more Al, Fe, Cu and Pb, showing less stability. The high internal angle of friction of zeolite did not vary with particle size and moisture, indicating funnel flow under gravity. For the second objective, hogs fed a zeolite diet produced manure with 15% and 22% less N and P, respectively, and demonstrated a better feed conversion, although not statistically significant (P>0.05). These results show that there is some potential in using high quality clinoptilolite in the ration of grower hogs.     

Purification of Proteins by the Use of Hydrophobic Zeolite Y

Hydrophobic zeolite Y can be used as a fast and efficient and inexpensive matrix in the purification of proteins from crude extracts. Preferably the zeolite can be used in the first purification step, replacing the commonly used precipitation techniques with (NH₄)₂SO₄ or ethanol. The time required for the zeolite prefractionation was a few hours compared to the much more time consuming precipitation procedure which demands centrifugation and subsequent dialysis. Proteins can be adsorbed on the zeolite either in order to remove undesired proteins or to be subsequently eluted from the zeolite in order to achieve purification and concentration. Removal of undesired proteins is exemplified by the purification of horseradish peroxidase from a crude extract. The zeolite procedure enhanced the specific activity five times and provided a yield similar to that which was obtained by the use of standard procedures, (NH₄)₂SO₄ fractionation and ion-exchange chromatography. Binding and subsequent elution of proteins from the zeolite is exemplified by the purification of monoclonal antibodies from hybridoma culture supernatants. Proteins were desorbed from the zeolite by the use of polyethylene glycol 600 and this procedure yielded a purification factor of 5.     

The use of zeolites as slow release anthelmintic carriers

This work examines the ability of commercial zeolite Y to act as a slow release agent for a number of anthelmintic drugs. Administration to rats, dosed with Nippostrongylus brasiliensis, of pyrantel and/or fenbendazole and pigs, dosed with Ascaris and Oesophagostomum, of dichlorvos (DDVP) loaded onto zeolite Y was more successful in killing adult worms than administration of the pure drug alone. The zeolite Y was used as supplied for initial studies and then later dealuminated for further studies. The drug loadings were monitored by thermal analysis and the loaded zeolites were used in several field trials. The results indicate that zeolite Y is a suitable vehicle for the slow release of some anthelmintics. The slow release of drug from the zeolite matrix improved its efficacy.     

改性沸石粉吸附去除微污染水中Ni(Ⅱ)的试验研究

用壳聚糖改性天然沸石粉,制备了改性沸石粉吸附材料,对微污染水源水中微量镍(Ⅱ)的吸附去除进行了研究。考察了吸附时间、沸石粉投加量、镍(Ⅱ)初始浓度以及原水pH 值等因素对镍(Ⅱ)去除效果的影响。结果表明,改性沸石粉对镍(Ⅱ)的去除效果明显优于天然沸石粉;当镍(Ⅱ)初始浓度低于0.2 mg/L 时, 投加1.5 g/L 壳聚糖改性沸石粉,经20 min 吸附后,水中镍(Ⅱ)的剩余浓度低于 0.02 mg/L,可满足《生活饮用水卫生标准》(GB5749-2006)中的要求;提高水的pH 值有利于两种沸石粉对镍(Ⅱ)的去除。另外,两种沸石粉对镍(Ⅱ)的吸附过程均符合Freudlich 等温吸附模型,且改性沸石粉的吸附指数更小,其吸附能力更强。     

Combined use of biocontrol agents and zeolite as a management strategy against <Emphasis Type="Italic">Fusarium</Emphasis> and <Emphasis Type="Italic">Verticillium</Emphasis> wilt

Vascular wilt pathogens, like Fusarium oxysporum and Verticillium dahliae, cause heavy economic loses to a range of crops. The lack of chemical control intensifies the problem. In the present study, the initial in vitro activity of 134 bacterial isolates, originating from various stages of the composting process of cotton residues, against F. oxysporum f. sp. melonis (FOM) and V. dahliae was evaluated. The most efficient strains, named SP10 and C20 M, belong to Bacillus sp. Both strains significantly reduced Fusarium and Vertilicillium wilt in melon and aubergine respectively. Furthermore, zeolite was tested alone or in combination with SP10 against V. dahliae and FOM. It was shown that the combination of zeolite and SP10 in the transplant soil plug was the most disease suppressive treatment. Interestingly the single application of zeolite was also plant-protective. The positive effect of zeolite on plant health could be linked with the recorded up-regulation of plant defense genes.     

Anammox-zeolite system acting as buffer to achieve stable effluent nitrogen values

For a successful nitrogen removal, Anammox process needs to be established in line with a stable partial nitritation pretreatment unit since wastewater influent is mostly unsuitable for direct treatment by Anammox. Partial nitritation is, however, a critical bottleneck for the nitrogen removal since it is often difficult to maintain the right proportions of NO₂-N and NH₄-N during long periods of time for Anammox process. This study investigated the potential of Anammox-zeolite biofilter to buffer inequalities in nitrite and ammonium nitrogen in the influent feed. Anammox-zeolite biofilter combines the ion-exchange property of zeolite with the biological removal by Anammox process. Continuous-flow biofilter was operated for 570 days to test the response of Anammox-zeolite system for irregular ammonium and nitrite nitrogen entries. The reactor demonstrated stable and high nitrogen removal efficiencies (approximately 95 %) even when the influent NO₂-N to NH₄-N ratios were far from the stoichiometric ratio for Anammox reaction (i.e. NO₂-N to NH₄-N ranging from 0 to infinity). This is achieved by the sorption of surplus NH₄-N by zeolite particles in case ammonium rich influent came in excess with respect to Anammox stoichiometry. Similarly, when ammonium-poor influent is fed to the reactor, ammonium desorption took place due to shifts in ion-exchange equilibrium and deficient amount were supplied by previously sorbed NH₄-N. Here, zeolite acted as a preserving reservoir of ammonium where both sorption and desorption took place when needed and this caused the Anammox-zeolite system to act as a buffer system to generate a stable effluent.     

负载金属离子的5A 沸石的体外抗菌实验

目的:探讨负载金属离子的5A沸石的体外抗菌作用。方法:选用金黄色葡萄球菌、铜绿假单孢菌、白色念珠菌,利用倍比稀释法对5A沸石组、磺胺嘧啶银组及载不同浓度Ag+、Zn2+5A沸石共15组进行了体外抗菌试验研究,确定最佳抗菌效果离子负载方案。结果:三种细菌的MIC,双金属离子负载在抗菌上具有协同载Ag+5A沸石分别达到了125μg/ml~500μg/ml、31.25μg/ml~500μg/ml、250μg/ml~500μg/ml;附载Zn2+5A沸石分别达到了12.5mg/ml~25mg/ml、6.25mg/ml~50mg/ml、25mg/ml;负载双离子5A沸石分别为250μg/ml~500μg/ml、62.5μg/ml~500μg/ml、500μg/ml。结论:5A沸石负载金属离子后均具有抗菌作用,且抗菌作用与附载金属离子的量正相关;负载相同质量Ag+的5A沸石较附载Zn2+者具有更强的抗菌作用;双金属离子负载在抗菌上具有协同作用;2%Ag++8%Zn2+与2%Ag++10%Zn2+及4%载银组与阳性对照组无显著性差异。     

Antimicrobial action and efficiency of silver-loaded zeolite X

Aims: To synthesize silver-loaded zeolite X and establish the extent to which it persist in its antimicrobial action against strains of Escherichia coli K12W-T, Pseudomonas aeruginosa NCIMB8295 and Staphylococcus aureus NCIMB6571. Methods and Results: The antimicrobial action and efficacy of silver-loaded zeolite X on Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were investigated. Zeolite X was synthesized and loaded with Ag⁺ by ion exchange. This resulted in 2·0% (w/w) loading of Ag⁺ in the zeolite framework and 5·8% (w/w) on the zeolite. Escherichia coli and Pseudomonas aeruginosa and Staphylococcus aureus suspended in tryptone soya broth were exposed to 0·15, 0·25, 0·5 or 1·0 g l⁻¹ of silver-loaded zeolite X for a period up to 24 h. No viable cells were detected for any of the three micro-organisms within 1 h. Silver-loaded zeolite X, retrieved three times from the first exposure cultures, was washed with de-ionized water and added to fresh bacterial suspensions. The results showed that the silver-loaded zeolite X retained its antimicrobial action. Conclusions: Silver-loaded zeolite X persisted in its antimicrobial action against all three micro-organisms. Significance and Impact of the study: The results are significant for the longevity of antimicrobial action of silver-loaded zeolite X.     

Ammonium exchange and bioregeneration of bio-flocculated zeolite in a sequencing batch reactor

Natural zeolite was added to the sequencing batch reactors to assess its role in ammonium exchange. Even though the biofilm was fully developed on the zeolite surface, ammonium removal and the biological regeneration of the zeolite occurred constantly during the anoxic-fill phase and the reaction phase, respectively. However, the specific nitrification rate of the bio-flocculated zeolite was lower than that observed in the control on account of the limited ammonium release to the liquid phase.