Natural Clinoptilolite/KOH: An Efficient Heterogeneous Catalyst for Carboxymethylation of Hemicellulose

Fundamental properties and sustainable applications of the natural zeolite clinoptilolite

This review explores a set of sustainable applications of clinoptilolite, a natural zeolite abundant around the world in different localities. Thanks to its physico-chemical properties this material is extremely versatile for several applications, ranging from environmental catalysis and CO2 removal to industrial and agricultural wastewater purification, aquaculture, animal feeding, and food industry but also medical applications and energy storage systems. Due to the presence of cations in its framework, it is possible to tune the material's features making it suitable for adsorbing specific compounds. Thus, this review aims to provide insight into developing new technologies based on the use of this material that is sustainable, not harmful for humans and animals, naturally abundant, and above all cost-effective. Furthermore, it is intended to promote the use of natural materials in various areas with a view to sustainability and to reduce as far as possible the use of chemicals or other materials whose synthesis process can have a polluting effect on the environment.

Structural elucidation of hemicelluloses from oil-tea camellia fruit shell

Oil-tea camellia fruit shell (CFS) is a very abundant waste lignocellulosic resource. The current treatments of CFS, i.e. composting and burning, pose a severe threat on environment. Up to 50 % of the dry mass of CFS is composed of hemicelluloses. However, chemical structures of the hemicelluloses in CFS have not been extensively studied, which limits their high-value utilization. In this study, different types of hemicelluloses were isolated from CFS through alkali fractionation with the assistance of Ba(OH)2 and H3BO3. Xylan, galacto-glucomannan and xyloglucan were found to be the major hemicelluloses in CFS. Through methylation, HSQC and HMBC analyses, we have found that the xylan in CFS is composed of →4)-β-D-Xylp-(1→ and →3,4)-β-D-Xylp-(1→ linked by (1→4)-β glycosidic bond as the main chain; the side chains are α-L-Fucp-(1→, →5)-α-L-Araf-(1→, β-D-Xylp-(1→, α-L-Rhap-(1→ and 4-O-Me-α-D-GlcpA-(1→, connected to the main chain through (1→3) glycosidic bond. The main chain of galacto-glucomannan in CFS consists of →6)-β-D-Glcp-(1→, →4)-β-D-Glcp-(1→, →4,6)-β-D-Glcp-(1→ and →4)-β-D-Manp-(1→; the side chains are β-D-Glcp-(1→, →2)-β-D-Galp-(1→, β-D-Manp-(1→ and →6)-β-D-Galp-(1→ connected to the main chain through (1→6) glycosidic bonds. Moreover, galactose residues are connected by α-L-Fucp-(1→. The main chain of xyloglucan is composed of →4)-β-D-Glcp-(1→, →4,6)-β-D-Glcp-(1→ and →6)-β-D-Glcp-(1→; the side groups, i.e. β-D-Xylp-(1→ and →4)-β-D-Xylp-(1→, are connected to the main chain by (1→6) glycosidic bond; →2)-β-D-Galp-(1→ and α-L-Fucp-(1→ can also connect to →4)-β-D-Xylp-(1→ forming di- or trisaccharide side chains.

Production of biodiesel from salvia mirzayanii oil via electrolysis using KOH/Clinoptilolite as catalyst

BACKGROUNDS

In recent years, fossil fuels are the main energy supply in both transportation and industry. Their increasing consumption has been causing global warming and acid raining. One of the alternative fuels that is considered today is biodiesel, which is clean and eco-friendly. The main method for biodiesel production is transesterification reaction of triglyceride oil with methanol in the presence of a suitable catalyst.

METHOD

In this research, biodiesel was produced from Salvia mirzayanii oil in the presence of KOH/Clinoptilolite catalyst. The impregnation, hydrothermal, and incipient wetness methods were used for loading KOH on the Clinoptilolite support to produce biodiesel via electrolysis method. The characteristics of the KOH/Clinoptilolite catalyst were examined through scanning electron microscopy (SEM), energy dispersive X-ray Spectroscopy (EDX), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analyses. The effects of key parameters including catalyst amount, methanol to oil molar ration, reaction time, reaction temperature, co-solvent type and its proportion, electrolysis voltage, catalyst reusability, and KOH concentration were examined on the biodiesel yield.

RESULTS

The results of elemental analysis confirmed that KOH was well loaded on Clinoptilolite support. The highest yield of biodiesel was obtained 79% in the presence of 10 wt% catalyst, alcohol to oil ratio of 9:1, acetone concentration of 10 wt%, temperature of 60 °C, and voltage of 10 V. The results of GC-MS, FTIR and H-NMR analyses illustrated that biodiesel as a product was produced with good quality.

CONCLUSION

Based on the obtained results, in all three methods of catalyst synthesis KOH was loaded on Clinoptilolite support but at the end of the transesterification reaction only the catalyst synthesis via incipient wetness method could be reused three times under optimum reaction conditions. The produced biodiesel had high quality, whose physical and chemical properties had good agreement with ASTM, EN 14214, IS 15607 standards. Since the salvia mirzayanii oil is an appropriate feedstock source for biodiesel production, it is suggested to use salvia mirzayanii oil and KOH/Clinoptilolite catalyst to produce biodiesel on industrial scale.

Efficient separation of bagasse lignin by freeze-thaw-assisted p-toluenesulfonic acid pretreatment

Lignin separation is an important procedure that benefits multiple industries and in particular biomass transformation efforts. In this study, bagasse lignin was separated by freeze-thaw-assisted p-toluenesulfonic acid (p-TsOH) pretreatment. The optimal conditions were freezing temperature -60 °C, freezing time 8.0 h, thawing temperature 15 °C, p-TsOH concentration 60%, pretreatment temperature 70 °C, and time 20 min. Lower acid concentrations and temperatures were used compared with traditional p-TsOH pretreatment. The efficiency and selectivity of lignin separation were improved. It was attributed to freeze-thawing, which provided a more efficient physical channel for the effective penetration of p-TsOH. The separation, extraction and purity of lignin were improved to 89.76%, 78.22% and 77.89%, respectively. High separation, high extraction, high purity and large molecular weight lignin samples were obtained. In addition, the recovery and reuse of p-TsOH was enhanced. This provided a new method for the efficient and clean separation of lignin.

Explorations on Thermodynamic and Kinetic Performances of Various Cationic Exchange Durations for Synthetic Clinoptilolite

Various cation–exchanged clinoptilolites (M–CPs, M = Li⁺, Cs⁺, Ca²⁺, Sr²⁺) were prepared, and their exchanged thermodynamic (and kinetic) properties and adsorption performances for CH₄, N₂, and CO₂ were investigated. The results demonstrated that the relative crystallinity of M–CP_S decreased with the increase of exchange times. Their chemisorbed water weight loss gradually increased with the increasing exchange times, except that of Cs–x–CP. The Δ_rGmθ values of exchange process of Li⁺, Cs⁺, Ca²⁺, or Sr² presented the increased trend with the enhanced exchange times, but they decreased as the temperature increased. The negative Δ_rGmθ values and the positive Δ_rHmθ and Δ_rSmθ values suggested that the exchanged procedure belonged to spontaneous, endothermic, and entropy-increasing behaviors; their kinetic performances followed a pseudo–second–order model. However, the calculated E_a values of exchange process showed the increased tendencies with the enhanced exchange times, indicating that the exchange process became more difficult. Finally, the preliminary adsorption results indicated that the maximum adsorption amount at 273 K and 1 bar was 0.51 mmol/g of CH₄ and 0.38 mmol/g of N₂ by (Na, K)–CP, and 2.32 mmol/g of CO₂ by Li–6–CP.

Co-MOF-74 based Co3O4/cellulose derivative membrane as dual-functional catalyst for colorimetric detection and degradation of phenol

Smart nanomaterials that can simultaneously detect and eliminate contaminants in water environment are significant for health protection. To achieve such goal, Co-MOF-74 was in-situ assembled on regenerated cellulose membranes followed by calcination process, thus achieving dual-functional Co₃O₄/cellulose derivative membrane (Co₃O₄/CDM) catalyst. The Co₃O₄ morphology was readily controlled by further recrystallization of the deposited MOF precursor. Combining the high enrichment ability of cellulose membrane and outstanding peroxidase-active of Co₃O₄, the fast color reaction for phenol was accomplished within 10 min by Co₃O₄/CDM with the assistance of H₂O₂ and 4-aminoantipyrine (4-AAP). Moreover, the Co₃O₄/CDM also portrayed an excellent degradation property for phenol elimination via sulfate radical-advanced oxidation processes (SR-AOPs). The degradation efficiency of phenol reached 93% in 20 min, and the possible mineralization mechanism was proposed based on the XPS and LC-MS analysis. Thus, Co-MOF-74 derived Co₃O₄/CDM shows excellent properties in aiding the colorimetric detection and degradation of phenol in aqueous solutions.

Extended Release of Metronidazole Drug Using Chitosan/Graphene Oxide Bionanocomposite Beads as the Drug Carrier

This study depicts the facile approach for the synthesis of chitosan/graphene oxide bionanocomposite (Chi/GO) beads via the gelation process. This is the first-ever study in which these Chi/GO beads have been utilized as a drug carrier for the oral drug delivery of metronidazole (MTD) drug, and investigations were made regarding the release pattern of the MTD drug using these Chi/GO beads as a drug carrier for a prolonged period of 84 h. The MTD is loaded on the surface as well as the cavity of the Chi/GO beads to result in MTD-Chi/GO bionanocomposite beads. The MTD drug loading was found to be 683 mg/g. Furthermore, the in vitro release patterns of pure drug and the drug encapsulated with Chi/GO beads are explored in simulated gastric as well as simulated intestinal fluids with phosphate-buffered saline (PBS) of pH 1.2 and 7.4, respectively. As-synthesized bionanocomposite beads have shown excellent stability and capacity for extended release of the MTD drug as compared to the pure drug in terms of bioavailability in both media. The cumulative release data are fitted with the Korsmeyer-Peppas kinetics and first-order reaction kinetics at pH 1.2 and 7.4. The synthesized bionanocomposite beads have good potential to minimize the multiple-dose frequency with the sustained drug release property and can reduce the side effects due to the drug.

Green, efficient extraction of bamboo hemicellulose using freeze-thaw assisted alkali treatment

The premise of high value utilization of lignocellulosic biomass is effective separation of hemicellulose. In this paper, the extraction of bamboo hemicellulose using freeze-thaw assisted alkali treatment (FAT) was studied. The effect of alkali concentration, alkali treatment time, freezing temperature, and freeze-thaw time on the main components was studied. Bamboo was frozen at -30 °C for 12 h, thawed at room temperature, and then treated at 75 °C for 90 min with 7.0% alkali. The extraction rate of hemicellulose was as high as 64.71%. The purity of hemicellulose samples using conventional AT decreased from 82.63% to 78.56%. Hemicellulose with the same yield as that of conventional alkali treatment was obtained by further reducing the alkali concentration. The purity of hemicellulose samples increased from 82.63% to 89.45%. It had a higher purity, higher molecular weight, and lower polydispersity. A new, green and efficient alkaline extraction method for hemicellulose was developed.

Synthesis of Chitosan/Diatomite Composite as an Advanced Delivery System for Ibuprofen Drug; Equilibrium Studies and the Release Profile

Chitosan/diatomite nanocomposite (CS/D) was synthesized as a low-cost and highly porous structure of enhanced physicochemical properties to be applied as advanced carriers for ibuprofen drug (IB). The loading properties of CS/D were studied in comparison to diatomite as a separated phase and achieved a loading capacity of 562.6 mg/g. The loading reactions of IB into CS/D show pseudo-second-order kinetic behavior and Langmuir isotherm properties. This demonstrates homogeneous loading processes in monolayer forms and controlled essentially by physical mechanisms. This was confirmed by the calculated Gaussian energy (7.7 kJ/mol (D) and 7.9 kJ/mol (CS/D)) in addition to the thermodynamic parameters. The thermodynamic behavior for the IB loading process is related to spontaneous, favorable, and exothermic reactions. The CS/D composite is of promising IB release profile that extended to about 200 h with a maximum release of 91.5% at the gastric fluid (pH 1.2) and 97.3% in the intestinal fluid (pH 7.4). The IB release rate from CS/D can be controlled based on the ratio of the integrated chitosan in the composite. The IB release reactions from CS/D follow the assumption of Korsmeyer-Peppas kinetics with determined values for the diffusion exponent reflects complex diffusion and erosion as the affected mechanisms during the IB release process.

Pd (II) Immobilized on Clinoptilolite as a Highly Active Heterogeneous Catalyst for Ullmann Coupling-type S-arylation of Thiols with Aryl Halides

BACKGROUND

There are a number of protocols for Ullmann coupling-type S-arylation reactions, many of them suffer from the use of homogenous and often corrosive catalyst, cumbersome workup procedures, and long reaction times. Besides, many of these reagents are expensive and non-recoverable, leading to the generation of a large amount of toxic waste particularly when large-scale applications are considered.

OBJECTIVE

The aim of this study was to prepare a new Pd catalyst bonded on the surface of zeolite as a heterogeneous catalyst.

METHODS

A heterogeneous palladium catalyst has been prepared by immobilizing Pd ions on Clinoptilolite. This novel developed heterogeneous catalyst was thoroughly examined for Ullmann coupling-type S-arylation reaction using different bases, solvents and 0.003 mg of the catalyst. The structural and morphological characterizations of the catalyst were carried out using XRD, TGA, BET and TEM techniques.

RESULTS

Highly efficient heterogeneous palladium catalyst has been developed by immobilizing Pd ions on Clinoptilolite, as one of the most abundant naturally occurring zeolites for Ullmann Sarylation. By using this method, we provide an efficient way to a wide variety of substituted thiolic compounds. Moreover, the catalyst is easily recovered using simple filtration and reused for 5 consecutive runs.

CONCLUSION

In this effort, we developed a new Pd catalyst bonded on the surface of zeolite as a substrate to prepare the heterogeneous catalyst. We demonstrate that this novel catalyst offers reliable and convincing data that may offer a valuable application in further developing the science and technology of Ullmann reaction protocols and allied industries. Additionally, the catalyst was reusable and kept its high activities over a number of cycles.