Berrin Bozan

Quercetin (QC) is a biologically active flavonoid widely investigated for cardiovascular, ocular, antiallergic, antiarthritic, and anticancer applications. In this study, montmorillonite (MMT) clay was used as a cost‐effective and environmentally friendly adsorbent for QC. To improve its surface properties and adsorption performance, MMT was modified using three surfactants from different classes: cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, sodium dodecyl sulphate (SDS) as an anionic surfactant, and Triton X‐100 as a nonionic surfactant. The prepared materials were characterized by FTIR, XRD, and TGA analyses to evaluate the effect of surfactant modification on the structural and surface properties of MMT. The adsorption capacities of MMT, MMT‐CTAB, MMT‐SDS, and MMT‐Triton X‐100 were determined to be 142.386, 165.336, 145.641, and 162.589 mg/g, respectively. Surfactant modification enhanced QC adsorption, with MMT‐CTAB exhibiting the highest capacity. For MMT‐CTAB, the adsorption conditions were optimized using the Box–Behnken design, and a maximum adsorption capacity of 189.837 mg/g was obtained at pH 6.6, 55°C, and an initial QC concentration of 500 mg/L. Sequential adsorption–desorption experiments demonstrated that CTAB‐modified MMT maintained its adsorption performance over five consecutive cycles. Overall, CTAB‐modified MMT exhibited the most promising QC adsorption performance among the modified samples.

In this study, chitosan-based hydroxyapatite/chitosan (HAP/CHI), cellulose/chitosan (CEL/CHI) and montmorillonite/chitosan (MMT/CHI) composites were synthesized and characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA). Acetylsalicylic acid (ASA) was used as a drug for loading and desorption studies to determine the release behavior of the synthesized composites. The maximum adsorption capacities (qe) were obtained as 251.5 mg/g, 197.7 mg/g and 288.95 mg/g for HAP/CHI, CEL/CHI and MMT/CHI, respectively. In vitro release studies of ASA from the composites HAP/CHI, CEL/CHI, and MMT/CHI were carried out phosphate buffer solution (PBS) and gastric juice (GJ). In the intestinal medium (PBS) controlled drug release continued for 72 hours (4320 minutes), and burst release was observed in the first 5 minutes in all composites. 19.16%, 47.15% and 37.32% of the active ingredient from HAP/CHI, CEL/CHI and MMT/CHI composites, respectively, were released in the first 5 minutes. After 5 minutes, the release slowed down and became more controlled for all three composites. At the end of the release, the highest releasing composite was CEL/CHI, with 95.77% ASA release. A total drug release of 87.48% was achieved with MMT/CHI and 87.37% with HAP/CHI. In the gastric environment (GJ) Controlled drug release continued for 72 hours (4320 minutes), and burst release was observed in the first 5 minutes in all composites. 52.51%, 72.30% and 44.87% of the active ingredient from HAP/CHI, CEL/CHI and MMT/CHI composites, respectively, were released in the first 5 minutes. After 5 minutes, the release slowed down and became more controlled for all three composites. At the end of the release, the highest releasing capacity was found with the CEL/CHI composite, with 96.05% ASA release. A total drug release of 93.26% was achieved with HAP/CHI and 84.89% with MMT/CHI.

In this study, which incorporates many principles of green chemistry (use of renewable feedstocks, catalysis, improvement of energy efficiency, and harmless solvents and auxiliaries), the single-phase catalytic conversion of cellulose to 5-HMF in over silica-alumina catalysts was investigated. A series of dual-template silica-alumina catalysts with CTAB as the main template and F127 or triethylamine (TEA) as the co-template were synthesized at a low temperature of 60 °C and characterized by XRD, N2 adsorption-desorption technique, FT-IR and pyridine adsorption FT-IR. The surface area is increased by using the second template in silica-alumina catalyst. In addition, the acidity of the surface was changed by using the second template. The cellulose conversion and yield of 5-HMF increased from 36% to 52% and from 3.13% to 4.24%, respectively, due to the properties gained by using the second template. 52% cellulose conversion and 8.13% selectivity of 5-HMF were obtained in aqueous medium, 220 °C and 6 h reaction time with the catalyst using TEA as co-template. Eco-friendly silica catalysts synthesized at low temperatures with a dual template can be considered as a potential alternative for the conversion of cellulose into value-added biobased products.

Catalysts are very important in the use of cellulose, the main component of biomass, as a raw material for the large-scale production of liquid fuels and chemicals. 5-Hydroxymethylfurfural (HMF) is an extremely important intermediate in the fine chemical industry. HMF can be synthesized by acid-catalyzed dehydration of fructose, glucose, cellulose, or sucrose. The conversion of cellulose to HMF is challenging due to its chemical structure. The objective of the present study was to devise a more facile synthesis method using transition metal-doped montmorillonite catalysts (10Cr-Mnt, 10Cu-Mnt, 10Fe-Mnt, and 10Zn-Mnt) by wet impregnation. Samples were characterized by X-ray powder diffraction, specific surface area, and NH₃-TPD analyses. The synthesized catalysts were used for the conversion of cellulose to 5-HMF in an aqueous medium. Among the metals studied, Cr showed the greatest catalytic activity. With the use of this catalyst, efficient conversion of cellulose to 5-HMF was achieved, affording a conversion yield of 93.47% and 5-HMF yield of 9.07% within 6 h at 200°C. The study described here could be useful for the efficient conversion of cellulose into 5-HMF, as well as into other biomass-derived chemicals.

In this study, transition metal doped montmorillonite catalyts (Cr-MMT, Cu-MMT, Fe-MMT and Zn-MMT) were successfully synthesized by hydrothermal method and evaluated for the conversion of cellulose to 5-HMF in the water media. Metal-MMT catalysts were characterized by XRD, BET, Ammonia-TPD and pyridine-FTIR to investigate the properties of the samples. Using Cr-MMT, an efficient conversion of cellulose to 5-HMF was achieved in the water system, affording a conversion yield 93.47% and 5-HMF yield 9.07% within 6 h at 200^oC.

Hazelnut shells, a high lignin containing biomass, were subjected to individual and sequential liquid hot water (LHW), alkaline (AP) and dilute acid pretreatments (DAP). Among the single pretreatments, LHW demonstrated the highest cellulose recovery of 98.1%, DAP resulted in the highest hemicellulose solubilization of 56.0%, and AP of the highest lignin removal of 49.6%. Employing two-step pretreatment on hazelnut shells, in general, demonstrated an enhanced action of the second pretreatment; therefore, the sequence of the pretreatment methods had a significant impact on both substrate characteristics and enzymatic hydrolysis efficiency of biomass. In terms of delignification, AP-LHW achieved 60.7% lignin removal, while LHW-DAP showed the highest hemicellulose removal of 93.8% and DAP-LHW resulted in the highest cellulose recovery of 94.0%. Structural properties of raw and pretreated hazelnut shells were observed by FTIR. The maximum glucose recovery of 54.9% was observed in DAP-LHW pretreated samples. For this pretreatment combination, almost 1.8 MJ total energy was required to recover 10.2 g glucose. The findings indicated that complete removal of the physical barrier of lignin and hemicellulose might not be essential; partial relocation of lignin and alteration of cellulose structure may also be efficient in increasing the sugar recovery from the lignocellulosic biomass.