Optimized synthesis of lignin sulfonate nanoparticles by solvent shifting method and their application for adsorptive removal of dye pollutant.

Synthesis of value added products from wastes is of importance from different perspectives. Wood and paper industry produces tons of wastewaters that contains lignin. In this paper, we report a new approach, called solvent-shifting method, to synthesize lignin sulfonate nanoparticles (LS-NPs). The effective parameters on size of LS-NPs were carefully tuned and the size of LS-NPs was minimized by response surface methodology. The results suggested that LS-NPs with size of 53 nm can be synthesized at low lignin sulfonate concentration (0.28 g/mL), moderate surfactant concentration (0.32 g/mL) but relatively high anti-solvent content (92 mL of ethanol for 40 mL of the aqueous phase). The as-synthesized LS-NPs were characterized by different analytical techniques, where presence of various negatively charged functional groups on surface of LS-NPs was conformed. To investigate the potential of LS-NPs for adsorptive removal of pollutant molecules, basic red 2 (known as Safranin-O) was used as a model pollutant dye. The results suggested that the maximum removal occurs at alkaline pH, where there is strong electrostatic interactions between LS-NPs and cationic Safranin-O molecules. The adsorption capacity was 85.14 mg/gr, where the isotherm data was best described by Redlich-Peterson isotherm model. The kinetic data also revealed that the adsorption is very fast in the first 20 min, where there is three diffusional steps to complete the adsorption in 90 min. The results of this study could open up new window to the field of value-added products to synthesize waste-driven nanomaterials for environmental applications.

Study and optimization of parameters affecting the acetylation process of lignin sulfonate biopolymer.

Here, firstly lignin sulfonate was produced from sulfite liquor provided by Mazandaran wood & paper industries (Chookam). Then, the role of effective parameters including reaction temperature, duration time, and amounts of pyridine and acetic anhydride respectively as the catalyst and the esterification agent on the acetylation rate of lignin sulfonate were studied and the process parameters were optimized through multiple experiments. In this investigation, using 1 g lignin sulfonate, the effect of various levels of temperature (ranged from room temperature to 140 °C), reaction time (12-72 h), pyridine volume (0-30 mL), and acetic anhydride volume (5-30 mL) were evaluated. Based on the results of several esterification processes, the optimal values of temperature and reaction time were obtained to be 100 °C and 48 h, respectively, and the optimal volumes of acetic anhydride and pyridine were 20 mL (with equal amounts). Besides, the characterization tests of lignin sulfonate and acetylated lignin sulfonate were performed using FT-IR and NMR techniques. Also in this paper, the morphology and crystallinity/amorphicity of lignin sulfonate and acetylated lignin sulfonate were examined using SEM images and XRD patterns.

Preparation and characterization of biodegradable lignin-sulfonate nanoparticles using the microemulsion method to enhance the acetylation efficiency of lignin-sulfonate.

In this study, a novel method is presented for producing lignin-sulfonate nanoparticles. Then, the effect of produced nanoparticles is investigated on enhancing the acetylation efficiency. For these purposes, lignin-sulfonate was isolated from black-liquor of pulp-and-paper mill wastewater. Next, lignin-sulfonate nanoparticles were obtained using the oil-in-water (O/W) microemulsion, followed by modification of micro/nano-lignin-sulfonate particles. The physical, chemical, and morphological properties of lignin sulfonate micro/nanoparticles and modified forms of both samples were analyzed using FTIR, DLS, FE-SEM, AFM, 1H NMR, and 13CNMR analyses. Surface morphology revealed that the nanoparticles were homogenized and spherical with an average diameter of 25.5 nm. The chemical structure of the nanoparticles was similar to that of the microparticles. On the other hand, the chemical structure of acetylated lignin-sulfonate was slightly different from that of unmodified samples. The results also showed that the production of nano-lignin-sulfonate increased the acetylation efficiency and reduced the time and temperature of acetylation.