Bentonite Binders Research Articles

Binder‐free Zeolite Beta Beads with Hierarchical Porosity: Synthesis and Application as Heterogeneous Catalysts for Anisole Acylation

AbstractThree zeolites (H‐Beta, H‐ZSM‐5 and H‐Y) were synthesized in the form of binder‐free macroscopic beads (d=215–840 μm) using a hydrothermal method employing anion‐exchange resin beads as hard template. The beads obtained after removal of the hard template by calcination consisted of crystalline zeolite domains connected with each other to form a hierarchical porous network in which the zeolitic micropores are accessible through meso‐ and macropores, as proven by characterization with XRD, N2 physisorption, SEM, and TEM. The composition, the nature and amount of acid sites and the degree of hydrophobicity of these beads were investigated by means of XRF, solid‐state NMR, pyridine‐FTIR and TGA. The zeolite beads were tested as heterogeneous catalysts in the Friedel‐Crafts acylation of anisole with acetic anhydride to produce para‐methoxyacetophenone. H‐Beta‐Beads displayed the best catalytic performance with 95 % conversion of acetic anhydride and 76 % yield of para‐methoxyacetophenone in a batch reactor test (90 °C, 6 h). Next, the catalytic performance of H‐Beta‐Beads was compared in both batch and continuous‐flow mode to extrudates prepared by mixing zeolite Beta powder with either kaolin or bentonite binders. H‐Beta‐Beads outperformed the extrudates in batch‐mode reactions and could be reused in multiple runs without discernible loss of activity. In the continuous‐flow test, H‐Beta‐Beads demonstrated higher average activity but deactivated more rapidly than the extrudates.

The effect of sodium alginate, lignosulfonate and bentonite binders on agglomeration performance and mechanical strength of micro-fine agricultural lime pellets

Agricultural lime (crushed limestone) is often applied to acidic soils as the release of carbonate ions neutralize acid forming compounds, such as those added during fertilizer addition. Agglomerated micro-fine limestone is an attractive alternative to powdered limestone, mitigating product losses as a result of windy conditions during application. This article examines the production of agglomerates using sodium alginate, lignosulfonate and bentonite binders for micro-fine CaCO3 powder. Central composite design was used to determine the optimal (i) amount of liquid, (ii) concentration of binder added to maximize the yield of agglomerates of 2–5.6 mm in diameter. Thereafter, four mechanical strength tests were carried out on the agglomerates, where strength was compared dependent on the binder and concentration thereof. The results show that lignosulfonate agglomerates performed the worst of the three binders, whereas agglomerates of >3 g/kg sodium alginate and 70 g/kg bentonite were acceptable in strength. While sodium alginate is a more expensive binder per gram, its high strength at relatively low levels may recommend its use industrially, contingent on economic modeling. This article successfully demonstrated the varying mechanical strengths of various limestone binders, which may assist with the development of novel soil amendment products.

The role of bentonite binders in single or concomitant mycotoxin contamination of chicken diets

Concomitant presence of mycotoxins is more likely to appear than a single mycotoxicosis since many mycotoxigenic fungi grow and produce their toxic metabolites under similar conditions.The present study was designed to evaluate the efficacy of 4 mycotoxin binders to protect meat-type chickens against single and concomitant administration in the feed of two mycotoxins, namely aflatoxin B1 (AFB1) and ochratoxin A (OTA) both at concentration of 0.1 mg/kg.A total of 440 as hatched, d-old, Ross 308 broilers were reared for 42 d. There were 11 dietary treatments. Chickens were fed on either an uncontaminated basal diet, basal diet and AFB1, basal with concomitant presence of AFB1 and OTA, basal diet and three binders A, B and C (1%) with or without AFB1 or basal diet and binder D (0.5%) with or without concomitant presence of AFB1 and OTA. Performance, carcass yield and several biochemical parameters were examined.Mycotoxin concentration in liver and breast muscle samples was determined. Broiler performance under concomitant mycotoxin contamination was poorer than that under single mycotoxicosis. Mycotoxin presence increased relative heart weight compared to that of broilers fed on uncontaminated diets. Only OTA and not AFB1 was detected and only in the liver. OTA concentration was four-fold lower in broilers fed on a diet with binder compared to those fed on contaminated diets without binder.In conclusion, the study revealed that binder composition and presence or not of multiple toxins may be important factors for optimum broiler performance under mycotoxicosis.

Polymeric and Bentonite Binders for Agglomerating Metallurgical Raw Materials and Foundry Mixtures

Polymeric and Bentonite Binders for Agglomerating Metallurgical Raw Materials and Foundry Mixtures

Ocena toplotne upornosti izbranih bentonitnih veziv

Ocena toplotne upornosti izbranih bentonitnih veziv

Optical microscopy analysis of briquette binders

Environmental requirements and demands from the coal industry have resulted in a boom in briquetting technology in China. In this work, a low-volatility bituminous coal from the Changcun mine and bentonite binders are used for briquetting. The compressive strength, impact strength, and thermal stability of briquettes made using different binder concentration are determined. The morphology and distribution of binders in briquettes are studied by optical microscopy and digital image-processing technologies. The concept of roundness is introduced to indicate the pressure to which the binders are subjected during briquetting. The influences of binder morphology on briquette strength are discussed. The binders are mainly in aggregated and dispersed forms, present in similar proportions in the briquettes. Aggregated binders with large differences in size are not well-distributed. Binder roundness values are concentrated between 1.5 and 4.0, which indicates that most aggregated binders are compressed and conform well to the surfaces of coal particles. A few binders had roundness value approximating 1 or above 4, which indicated that these were under little pressure or overloaded, respectively. The relationships between briquette strength and binder morphology show that aggregated binders are detrimental to mechanical strength while dispersed binders benefit briquetting.

The Behavior of Bentonite Binders for the Elevated and High Temperatures

Abstract Bentonite binders rank among the most widespread applied systems for the production of molds. Their resistance to high temperatures (thermal stability) is mainly defined by genesis of binders, chemical composition and the content of Montmorillonite. The aim of this contribution is to compare selected bentonite binders commonly used in the foundries of the Central European region, in different ways of the thermostability determination as a result of changes of the mechanical strengths of the bentonite bonded sand mixture.

Bentonite binders in the presence of mycotoxins: Results of in vitro preliminary tests and an in vivo broiler trial

The use of two bentonites differing in composition as potential binders of three mycotoxins present in broiler diets was examined with both an in vitro preliminary test and an in vivo trial. In the in vitro test, the adsorbing and desorbing ability of the two bentonites added at 1% was investigated. Concentrations of aflatoxin B1 (AFB1), ochratoxin A (OTA) and zearalenone (ZEA) were determined with LC–MS/MS and were 0.02ppm, 0.1ppm and 2ppm respectively. In the in vivo trial, a total of 300 day-old, as hatched, broilers were randomly distributed in five dietary treatments with four replicate pens per treatment. In T1 treatment, broilers were fed a basal diet with neither mycotoxins nor bentonite added; in T2 broilers were fed the same diet with 1% m/m bentonite A added. In T3, broilers were fed the same diet with 1% m/m bentonite A added and three mycotoxins (AFB1, OTA and ZEA) added at levels not exceeding the EU maximum. In T4 treatment, broilers were fed the same diet with 1% m/m of bentonite B added and in T5 broilers were fed the same diet with 1% m/m of bentonite B added and mycotoxins at the same levels. Broiler performance and several biochemical and hematological parameters were examined. The in vitro test indicated a complete adsorption of 0.02ppm AFB1 by both bentonites, present at 1%. No desorption was observed for AFB1. Adsorption and desorption of ZEA and OTA were low. The in vivo trial revealed that the overall performance of broilers did not differ between treatments. Aspartate aminotransferase was found lower in broilers fed mycotoxin contaminated diets but within normal range. The study revealed that the examined bentonites may maintain optimum broiler performance when mycotoxin levels present in the diet do not exceed EU limits and guidance values possibly by ameliorating the negative effects of other mycotoxins, not regulated by EU, present at the same time in the diet.

The bonding/strengthening mechanism of colemanite added organic binders in iron ore pelletization

The addition of boron compounds into pellet mix is proposed as a potential solution to overcome the insufficient compressive strengths of preheated and fired pellets produced with organic binders. Colemanite was tested as an alternative binder to bentonite either alone or in combination with some organic binders on magnetite pellets. The performances of the tested binders on pellet qualities: balling, wet pellet moisture content, drop number, compressive strengths and microstructure of pellets have been compared with the performances of reference bentonite binders. The results of the tests showed that the qualities of pellets are insufficient when organic binders and colemanite are used as binders alone. The former failed to provide sufficient preheated and fired pellet strengths, the latter failed in terms of wet and dry pellet quality. However, good quality wet, dry, preheated and fired pellets could be produced with the combination of these two binders. In addition, stronger pellets could be produced at lower firing temperatures like 1373K thanks to addition of colemanite. The bonding mechanism of colemanite containing pellets was examined by scanning electron microscopy. It was found that the improved preheated and fired compressive strengths of colemanite-added pellets were due to the physical melting of colemanite at the contact point of magnetite grains during thermal treatment.

Influences of Bentonite Modification Methods on the Physical and Chemical Properties of Bentonite

The current study focuses on the artificial modification of natural bentonite using pulping sodium, stacking sodium, extrusion sodium, wheel rolling sodium, and microwave sodium treatments. The effects of these methods on the physical and chemical properties of bentonite are investigated. The results indicate that the wheel rolling sodium treatment, which features the effects of extrusion and kneading, facilitated maximum separation and sodium treatment of Ca2+and Mg2+in the lattice of bentonite. This method produced highly efficient Ca-bentonite with full modification. When the wheel rolling sodium treatment was performed for 60 min, the modified bentonite exhibited a colloid index of 300 mL/3 g, swelling value of 275 mL/2 g, swelling volume of 94 mL/g, and 2 h water absorption of 755%. The modified bentonite has desirable cohesiveness, dilatability, suspension property, dispersibility, and high physical and chemical performances, which are suitable for use as iron ore concentrate pallet and casting bentonite binders.

Experiences gathered during reclamation of used water glass and bentonite sands in extra low and ambient temperature

A study is reported in which cryogenic temperatures are applied to intensify the mechanical reclamation of used foundry sand in experimental equipment that reproduces the abrasion, rubbing and crushing found in industrial processing. Results for used silica sands with bentonite and silicate (water-glass plus ethylene glycol) binders carried out at approximately –70°C and ambient temperature are presented. The reclaimed material was characterised by pH value, ADV (acid demand value) and Na2O content, which usefully define ease of reclamation, bending sand strength and compressive sand strength. Mechanical–cryogenic reclamation clearly improved the output for both sand types, utilising the hygroscopic behaviour of moulding sands to intensify the release of sand from the binder. The presence of a 'freezing' agent changes the volume of both binder and sand grains, leading to increased stresses on the surface and inside the grains, combined with higher brittleness of the binder material. Compared with current practice, the cryogenic procedure reduces reclamation times and confers environmental benefits. However, if not adequately controlled, mechanical–cryogenic reclamation of sands with water-glass or bentonite binders may lead to much quicker wear of the sand grains and formation of large volumes of dust.

Activated carbons with metal containing bentonite binders as adsorbents of hydrogen sulfide

Wood-based activated carbon was ground and mixed with 10% bentonite binders containing either iron, zinc or copper cations adsorbed within the interlayer space and/or on the external surface of bentonite flakes. To better understand the role of transition metals, carbon was also impregnated with iron, zinc and copper salts. The structure of materials after modification was determined using nitrogen adsorption. The modification resulted in a decrease in porosity, especially in micropore volume, as a result of combined mass dilution effect and adsorption/re-adsorption of metals in small pores. Introduction of bentonite binders containing adsorbed metal increased the capacity of carbon for hydrogen sulfide only in the case of material containing copper. Copper also significantly increases the performance of carbon as an H 2S adsorbent when impregnation is applied whereas the effects of other metals used in this study are much less pronounced. It is likely that copper present in the small pores acts as a catalyst for oxygen activation causing hydrogen sulfide oxidation. As a result of this process, elemental sulfur is formed which, when present in small pores, is oxidized to weakly adsorbed SO 2. The SO 2 is removed from the surface when continuous reaction with hydrogen sulfide occurs. Thus, even though binding carbon with spent bentonites after copper adsorption increases the capacity of carbon toward H 2S removal, the formation of SO 2, another undesirable pollutant, does detract somewhat from the procedure.

Laboratory studies for improving green ball strength in bentonite-bonded magnetite concentrate pellets

The performance of bentonite binders in magnetite concentrate balling has been difficult to predict due to a lack of understanding of the binding mechanisms and of the effects of water chemistry. Results are presented that indicate that the most effective binding occurs when the bentonite platelets slide past one another to form sheet-like or fiber-like structures, which is produced by compressive shear mixing. It has also been determined that the effects of water chemistry on bentonite performance are much greater than had previously been believed. This is because the water retained in magnetite filter cake has been shown to have a considerably higher concentration of ions (particularly calcium and magnesium) than was present in the bulk solution, and these ions strongly impact the swelling behavior of the bentonite. Results showing the benefits of fiber development and showing the effects of the water chemistry are presented. By taking advantage of bentonite fiber development and dealing with the effects of water chemistry, the strength of bentonite-bonded magnetite concentrate pellets can be increased. These studies have brought to light a number of previously unsuspected effects, which are critically important for further improving the theories of bentonite-binding behavior.