New and effective cassava bagasse-modified biochar to adsorb Food Red 17 and Acid Blue 9 dyes in a binary mixture.

A promissory technic for reducing environmental contaminants is the production of biochar from waste reuse and its application for water treatment. This study developed biochar (CWb) and NH4Cl-modified biochar (MCWb) using cassava residues as precursors. CWb and MCWb were characterized and evaluated in removing dyes (Acid Blue 9 and Food Red 17) in a binary system. The adsorbent demonstrated high adsorption capacity at all pH levels studied, showing its versatility regarding this process parameter. The equilibrium of all adsorption experiments was reached in 30 min. The adsorption process conformed to pseudo-first-order kinetics and extended Langmuir isotherm model. The thermodynamic adsorption experiments demonstrated that the adsorption process is physisorption, exhibiting exothermic and spontaneous characteristics. MCWb exhibited highly efficient and selective adsorption behavior towards the anionic dyes, indicating maximum adsorption capacity of 131 and 150 mg g-1 for Food Red 17 and Acid Blue 9, respectively. Besides, MCWb could be reused nine times, maintaining its original adsorption capacity. This study demonstrated an excellent adsorption capability of biochars in removing dyes. In addition, it indicated the recycling of wastes as a precursor of bio composts, a strategy for utilization in water treatment with binary systems. It showed the feasibility of the reuse capacity that indicated that the adsorbent may have many potential applications.

Influence of gelatin type on physicochemical properties of electrospun nanofibers.

This study explores the fabrication of nanofibers using different types of gelatins, including bovine, porcine, and fish gelatins. The gelatins exhibited distinct molecular weights and apparent viscosity values, leading to different entanglement behavior and nanofiber production. The electrospinning technique produced nanofibers with diameters from 47 to 274 nm. The electrospinning process induced conformational changes, reducing the overall crystallinity of the gelatin samples. However, porcine gelatin nanofibers exhibited enhanced molecular ordering. These findings highlight the potential of different gelatin types to produce nanofibers with distinct physicochemical properties. Overall, this study sheds light on the relationship between gelatin properties, electrospinning process conditions, and the resulting nanofiber characteristics, providing insights for tailored applications in various fields.

Chitosan-based nanofibers for enzyme immobilization.

The widespread application of soluble enzymes in industrial processes is considered restrict due to instability of enzymes outside optimum operating conditions. For instance, enzyme immobilization can overcome this issue. In fact, chitosan-based nanofibers have outstanding properties, which can improve the efficiency in enzyme immobilization and the stability of enzymes over a wide range of operating conditions. These properties include biodegradability, antimicrobial activity, non-toxicity, presence of functional groups (amino and hydroxyl), large surface area to volume ratio, enhanced porosity and mechanical properties, easy separations and reusability. Therefore, the present review explores the advantages and drawbacks concerning the different methods of enzyme immobilization, including adsorption, cross-linking and entrapment. All these strategies have questions that still need to be addressed, such as elucidation of adsorption mechanism (physisorption or chemisorption); effect of cross-linking reaction on intramolecular and intermolecular interactions and the effect of internal and external diffusional limitations on entrapment of enzymes. Moreover, the current review discusses the challenges and prospects regarding the application of chitosan-based nanofibers in enzyme immobilization, towards maximizing catalytic activity and lifetime.

Production of low molecular weight chitosan by acid and oxidative pathways: Effect on physicochemical properties.

Chitosan-based biomaterials with a low molecular weight (LMW) have been drawn attention due to the promising applications in the pharmaceutical and food fields. For this reason, the aim of this work was to study the effect of two distinct depolymerization pathways on the chitosan physicochemical properties. Chitosan was submitted to depolymerization reaction to obtain chitosan with low molecular weight (LMW), using the oxidative pathway (H2O2) and the acid pathway (HCl). The molecular weight reduction was investigated by kinetic study and chain scission mechanism. Chitosan characterization was performed according to its viscosimetric average molecular weight and deacetylation degree, respectively, through the viscosimetric method and proton nuclear magnetic resonance spectroscopy (1H NMR). The structural integrity was evaluated by Fourier transform infrared (FTIR) and energy dispersive spectroscopy (EDS). The crystalline and thermal properties were investigated, respectively, by X-ray diffraction (XRD) spectroscopy and thermogravimetric (TGA)/ differential thermal (DTA)/ differential scanning calorimetry (DSC) analysis. The water-chitosan interaction study was used to estimate the chitosan solubility. The results pointed out that both pathways resulted in chitosan with low molecular weight (<50 kDa). Moreover, the structural integrity of chitosan polymeric chains was preserved after depolymerization by oxidative pathway, while the acid pathway modified the polymer chain arrangement. Therefore, the chemical pathways resulted in two distinct low molecular weight chitosans, which allows different applications in food science.

Adsorption of a textile dye onto piaçava fibers: kinetic, equilibrium, thermodynamics, and application in simulated effluents.

This research was conducted to evaluate the methylene blue dye adsorption by piaçava fibers. The effects of adsorbent amount, pH, kinetics, equilibrium, and thermodynamics were analyzed, as well as the adsorbent performance in the treatment of synthetic textile effluents. The adsorbent characterization was also performed. Experimental kinetic data were fitted with pseudo-first-order, pseudo-second-order, and Elovich models. The equilibrium tests were done at 298, 308, and 318 K, and the models of Freundlich, Langmuir, Redlich-Peterson, and Sips were used. The adsorption was favored using 0.025 g of adsorbent, pH 10, and 318 K. The Elovich model provided better fit to kinetic data. The equilibrium experimental points were well represented by the Sips model. The maximum experimental adsorption capacity of methylene blue dye was 427.3 mg g-1. It was verified a spontaneous, favorable, and endothermic adsorption. Piaçava fiber was a promising low-cost material to be used for color removal in effluents containing methylene blue.

Preparation of carbonaceous materials from pyrolysis of chicken bones and its application for fuchsine adsorption.

Activated carbon and biochar were obtained from chicken bone (CB), characterized, and applied to remove basic fuchsine from aqueous media. The adsorbent dosage and pH effects were studied, as well as kinetic, equilibrium, and thermodynamic curves were constructed. The values of BET surface area and total pore volume were 108.94 m2 g-1 and 0.219 cm3 g-1 for the activated carbon and, 18.72 m2 g-1 and 0.075 cm3 g-1 for the biochar. The dye removal percentages were 93.63 and 55.38% when 2.5 g L-1 of activated carbon and biochar were used, respectively. The adsorption was favored using 0.5 g L-1 of adsorbent and pH of 7.0. Adsorption kinetics was well represented by the pseudo-second-order model. Langmuir model was the best to represent the equilibrium. Maximum adsorption capacity was 260.8 mg g-1, obtained using activated carbon. The process was endothermic, favorable, and spontaneous. Results showed that alternative carbonaceous materials can be obtained from chicken bones and used as adsorbents to treat colored effluents containing fuchsine.

Chitosan-functionalized nanofibers: A comprehensive review on challenges and prospects for food applications.

Chitosan exhibits outstanding properties, which allow a wide range of applications. For this reason, chitosan-based biomaterials have been developed over the years and, among these biomaterials, chitosan-based nanomaterials may significantly change the material properties, which could result in some exceptional features. Indeed, chitosan-based nanofibers have a larger surface area:volume ratio than the bulk materials at macro scale. Moreover, chitosan-based nanofibers could lead to enhanced porosity and mechanical properties, which could also improve surface functionalities, and consequently, the range of applications. However, the diversity in sources of raw materials and the production processes for the development of chitosan might provide distinct physicochemical characteristics. Because the varieties of chitosan have been limited in the most part the nanofibers synthesis, the current review describes an extensive research concerning the development of chitosan-based nanofibers and summarizes the different techniques for the nanofibers production; in addition to point out the effects of chitosan characteristics on the spinnability of the solution. Furthermore, the present review explores some potential studies in relation to the chitosan-based nanofibers applied to food technology, including active food packaging, nanofood carrier and enzyme immobilization.