| Mycotoxins arc highly toxic and carcinogenic metabolites produced by fungi or molds under suitable conditions,which are widely existed in feed and food products.It was reported that more than 60%of feed and food products in China were contaminated by mycotoxins.The presence of mycotoxins in feed not only leads to the decrease of feed conversion rate and growth rate of animals,but also causes immunosuppression and changes in organ relative quality,damages liver and kidney,and makes livestock susceptible to diseases and increases the mortality of livestock.Literatures found that montmorillonite exhibits adsorption performance to specific mycotoxins.Montmorillonite is a kind of naturally aboundant clay minerals with low price and high specific surface area.It has advantages of no drug residue,no hormones,and no side effects when applied as mycotoxins adsorbents.In addition to the selective adsorption of mycotoxins,montmorillonite also has a good adsorption effect on escherichia coli,vibrio cholerae,campylobacter jejuni,staphylococcus aureus,rotavirus and bile salts,which can effectively repair and improve the gastrointestinal mucosa's defense against pathogenic factors.Therefore,using montmorillonite as adsorbent is an effective solution to the mycotoxin contamination issue.However,natural montmorillonite shows specific adsorption property to mycotoxins.Montmorillonite is a kind of water-bearing layered aluminosilicate mineral,composed of two silicon-oxygen tetrahedrons sandwiched by an aluminum(magnesium)-oxygen(hydro-oxygen)octahedron.Because of isomorphous substitution,montmorillonite lamellar has permanent negative charge,which needs to adsorb cations in its interlayer domain to achieve charge balance.These cations are strongly hydrophilic inorganic ions such as Calcium,sodium,potassium and magnesium ions.Therefore,natural montmorillonite has a strong hydrophilicity and cation exchange,showing good adsorption property to polar aflatoxin,but barely no adsorption performance to weak polar zearalenone and vomitoxin.Due to the similar mycotoxin growth conditions,feed and its raw materials often contain two or more different characteristics of mycotoxins.The results showed that the toxicity of coexisting toxins was much higher than that of single mycotoxin.The interaction of several toxins may even produce toxicity superposition or synergistic effects.At present,mycotoxin pollution has caused great economic loss to agriculture and livestock and poultry breeding industry,as well as serious harm to human health and food safety.Therefore,how to reduce or eliminate mycotoxin in feed and its raw materials,especially the contamination of compound mycotoxin has become one of the important issues concerning people's livelihood and sustainable development in China.Based on the above research present situation and the reality demand,this paper uses the cationic,non-ionic and zwitterionic surfactant modified montmorillonite stone for parent montmorillonite adsorption material,in order to improve the material of mycotoxin adsorption performance,and further study of the nature and dosage of modifier and material structure,parents and the scientific relationship between adsorption performance,and parents montmorillonite on the polar and nonpolar adsorption mechanism of mycotoxin paper's main work and research results are as follows:(1)Screening and purification of mycotoxin adsorbent using montmorilloniteBased on the analysis of various properties of raw ore,anhui 1,Inner Mongolia 1 and liaoning bentonite were selected as raw materials for mycotoxin adsorbent,and the dressing process of scrubbing,dispersing and centrifugal separation was adopted.Under the optimized purification process,the montmorillonite was effectively enriched,the impurity particles were effectively removed,and the montmorillonite concentrate presented a flaking morphology.(2)Preparation and properties study on cationic montmorillonite adsorbentMono-chain OTAB and double-chain DODAC modified montmoronite were prepared by ion exchange method.The results showed that the properties and dosage of modifier had a significant influence on the material structure,zwtitterionic characteristics and adsorption performance.DODAC-Mts had larger spacing between layers than OTAB-Mts,better hydrophobicicy,and higher adsorption capacity for strong polarity AFB1 and weak polarity ZER.The amount of modifier increases,the interval between layers expands,the oil affinity increases,and the adsorption of AFB1 and ZER increased.The adsorption of strong polarity AFB1 by OTAB-Mt and DODAC-Mt fitted to Freundlich model.The maximum adsorption capacity increased from 0.51 mg/g of raw Mt to 3.00 and 3.35 mg/g.The adsorption of cationic-modified montmoronite on weakly polar ZER conformd to the Linear model.The maximum adsorption capacity of OTAB-Mt and DODAC-Mt on ZER increased from<0.7 mg/g of raw Mt to 48.97 and 52.57 mg/g.The adsorption enhancement mechanism is the hydrophobic interaction between organic matter introduced by modifier and ZER.(3)Preparation and properties study on nonionic montmorillonite adsorbentThe nonionic surfactant modified Mt was prepared on the basis of hydrogen-bonding.The results showed that the interaction of OP-10 molecules between the layers of montmorillonite expanded the spacing between the layers of nonionic montmorillonite,increased the organic carbon content,and the spatial configuration changed with the amount of OP-10.The spatial structure of nonionic modified montmorillonite had a crucial influence on the adsorption capacity of AFB1 and ZER.When the amount of OP-10 exceeded a certain concentration,the expansion of nonionic modified montmorillonite was not obvious,and the adsorption effect of AFB1 and ZER was not significantly improved.OP-10 modified montmorillonite has hydrophilic and hydrophilic amphiphilic properties.Nonionic modified montmorillonite of AFB1 enhanced adsorption effect,met the Langmuir adsorption isothermal adsorption model,which was single layer adsorption.0.5OP-10Mt and 1.0OP-Mt and 2.0OP-10Mt of strong polarity AFB1 saturated adsorption capacities were 2.78 mg,2.69 mg/g and 2.72 mg/g,the introduction of absorption enhancement mechanism of OP-10 organic matter and the hydrophobic interaction of AFB1 and montmorillonite interlayer cation and AFB1 dipole interaction.The adsorption effect of non-ionic modified montmoronite on weak polar ZER was enhanced,and the adsorption was in line with the Linear isothermal adsorption model.The saturated adsorption capacities of 0.5OP-10Mt,1.OOP-10Mt and 2.OOP-10Mt on ZER were 4.67 mg/g,8.54 mg/g and 8.34 mg/g,respectively.The adsorption enhancement mechanism was the hydrophobic interaction between organic matter and ZER introduced by OP-10.(4)Preparation and properties study on zwitterionic montmorillonite adsorbentBS-12 and LAB-35 modified montmorillonites were prepared based on the principle of electrostatic interaction.Dosage of modifier itself characteristic and the influence on the material structure,zwitterionic and adsorption performance significantly.Compared to BS-12/Mts,LAB-35/Mts had larger layer spacing,good lipophilicity,good adsorption effect of AFB1 and ZER.Increasing the dosage of modifier,modifying agent molecules in montmorillonite interlayer space configuration changes,material of AFB1 ascension was not obvious,the adsorption effect of ZER adsorption effect quickly before they were slowly rising.The adsorption efficiency of zwitterionic modified montmoronite on AFB1 and ZER was enhanced.The maximum adsorption capacities of 1.00 BS-12/Mt,1.50 BS-12/Mt,1.00 LAB-35/Mt and 1.50 LAB-35/Mt on AFB1 were 4.21mg/g,4.58mg/g,5.07mg/g and 6.23mg/g,respectively.Adsorption enhancement mechanism is the hydrophobic interaction of organic hydrophobic carbon chain on AFB1 and the ion dipole interaction of positive charge(interlayer cation,quaternary ammonium salt cation and protonated amide functional group)carried by modified materials on AFB1.The maximum adsorption capacities of 1.00 BS-12/Mt,1.50 BS-12/Mt,1.00 LAB-35/Mt and 1.50 LAB-35/Mt to ZER were 10.11 mg/g,15.30 mg/g,18.33 mg/g and 20.95 mg/g,respectively.By controlling the structure and dosage of modifier,the type and quantity of adsorption sites can be controlled effectively.The results of this study lay a theoretical and technical foundation for the controlled preparation and application of Mt adsorbents. |
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