Enhanced Performance of Lignin Recovery with a Carbon Dioxide Acidification Method.

Lignin particles were recovered from the bagasse soda pulping black liquor by acidification with carbon dioxide continuously fed in a semibatch reactor. An experimental model based on the response surface methodology was selected to investigate the effect of parameters and optimize the process for maximizing the lignin yield, and the physicochemical properties of the obtained lignin under the optimum conditions were investigated for further potential applications. A total of 15 experimental runs of three controlled parameters including temperature, pressure, and residence time were carried out based on the Box-Behnken design (BBD). The mathematic model for lignin yield prediction was successfully estimated at 99.7% accuracy. Temperature played a more significant role in lignin yield than pressure and residence time. Higher temperature could faciltate a higher lignin yield. Approximately 85 wt % lignin yield was obtained under the optimum conditions with a purity higher than 90%, high thermal stability, and slightly broad molecular weight distribution. The p-hydroxyphenyl-guaiacyl-syringyl (HGS)-type lignin structure and spherical shape were confirmed by Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM). These characteristics confirmed that the obtained lignin could be used in high-value products. Moreover, this work indicated that the CO2 acidification unit for lignin recovery could be efficiently improved for achieving high yield and purity from black liquor by adjustment of the process.

Photocatalytic degradation of pesticides by nanofibrous membranes fabricated by colloid-electrospinning.

Photocatalytic degradation of organic pollutants is a promising way to clean wastewater. Herein, we develop and compare two processes for fabricating nanofibrous membranes with photocatalytic properties. Hybrid nanofibers are produced by colloid-electrospinning and composed of metal oxide nanoparticles on sintered SiO2 nanoparticles. The latter serves as support for the photocatalyst and preserves the structural integrity of nanofibers. Adsorption of metal salts on crosslinked polymer/SiO2 fibers followed by calcination allows for the obtention of fibers with large amounts of metal oxide. Nanofibrous membranes with supported ZnO, In2O3, or mixture of both, display photocatalytic activity upon UV irradiation. The membranes can degrade a dye and an organophosphate pesticide more effectively than membranes directly fabricated from the calcination of metal oxides.

PEGylation of shellac-based nanocarriers for enhanced colloidal stability.

Shellac is a biomaterial obtained from secretion of lac insects. Nanoparticles based on shellac are prepared by nanoprecipitation and miniemulsion techniques. The corrosion inhibitor 2-mercaptobenzothiazole can be efficiently encapsulated in nanoparticles. Release kinetics of the inhibitor from the nanocarriers is controlled by pH of the surrounding environment as well as the introduction of other biopolymers such as lignin and zein. To overcome the low colloidal stability of shellac nanoparticles in saline conditions, shellac is conjugated with poly(ethylene glycol) moieties. After PEGylation, nanoparticles with higher critical aggregation concentration are obtained and provide release kinetics of 2-mercaptobenzothiazole similar to shellac nanoparticles.

Targeted Drug Delivery in Plants: Enzyme-Responsive Lignin Nanocarriers for the Curative Treatment of the Worldwide Grapevine Trunk Disease Esca.

Nanocarrier (NC)-mediated drug delivery is widely researched in medicine but to date has not been used in agriculture. The first curative NC-based treatment of the worldwide occurring grapevine trunk disease Esca, with more than 2 billion infected plants causing a loss yearly of $1.5 billion, is presented. To date, only repetitive spraying of fungicides is used to reduce chances of infection. This long-term treatment against Esca uses minimal amounts of fungicide encapsulated in biobased and biodegradable lignin NCs. A single trunk injection of <10 mg fungicide results in curing of an infected plant. Only upon Esca infection, ligninolytic enzymes, secreted by the Esca-associated fungi, degrade the lignin NC to release the fungicide. The specific antifungal activity is confirmed in vitro and in planta (in Vitis vinifera L. cv. 'Portugieser'). All treated plants prove to exhibit significantly fewer symptoms several weeks after treatment, and their condition is monitored for 5 years (2014-2018), proving a long-term curative effect of this NC treatment. This study proves the efficacy of this NC-mediated drug delivery for agriculture, using a minimum amount of fungicides. It is believed that this concept can be extended to other plant diseases worldwide to reduce extensive spraying of agrochemicals.

Morphology-Controlled Synthesis of Lignin Nanocarriers for Drug Delivery and Carbon Materials.

Lignin is an abundant biopolymer that is mainly burned for energy production today. However, using it as a polyfunctional macromolecular building block would be desirable. Herein, Kraft lignin was modified through esterification of its hydroxyl groups with methacrylic anhydride. Then lignin nanocarriers with different morphologies (solid nanoparticles, core-shell structures, porous nanoparticles) were produced by a combination of miniemulsion polymerization and a solvent evaporation process. A UV-active cargo is used as a drug model to investigate the release behavior of the lignin nanocarriers depending on their morphology. To prove the enzymatic response of the lignin nanocarriers, we tested the enzyme laccase as a trigger to release the encapsulated cargo. Furthermore, porous lignin nanoparticles with high surface area were produced by carbonization. The carbon material has a high potential as an adsorbent, which was studied by adsorption tests with methylene blue. These biodegradable nanocarriers based on the polyfunctional bioresource lignin may find useful application as novel drug delivery vehicle in agriculture or as carbon materials for water purification.