Facile and eco-friendly fabrication of hierarchical superhydrophobic coating from eggshell biowaste

This study reports a facile and sustainable approach to fabricate superhydrophobic coating from eggshell biowaste. The coating was prepared by ball milling chicken eggshells, composed of hydrophilic calcium carbonate (CaCO₃), to microsized particles followed by surface hydrophobilizing with stearic acid (C₁₇H₃₅COOH) to form low surface energy nanosized calcium stearate ((C₁₇H₃₅COO)₂Ca) through the esterification of hydroxyl groups (-OH) absorbed on a surface of CaCO₃ with carboxyl groups (–COOH) of stearic acid. Then, a layer of modified eggshell particles dispersed in polystyrene (PS) binder was dip-coated on a substrate. A coated surface with water contact angles of 151° ± 1° on glass and 153° ± 1° on cotton fabric substrates was achieved when a 4:1 weight ratio of the modified eggshell:PS was used. The uniform distribution of the modified eggshell particles throughout the coating led to a surface with high degree of hierarchical micro-nanoscale roughness which resulted in superhydrophobicity. The superhydrophobic eggshell coating showed good environmental stability, self-cleaning, and oil/water separation properties. These results suggest that eggshell biowaste can be utilized for superhydrophobic applications.     

Interfacial polymerization of polyaniline and its layer‐by‐layer assembly into polyelectrolytes multilayer thin‐films

The layer‐by‐layer (LbL) self assembly deposition technique was used to prepare multilayer thin films of anionic polyaniline‐blend‐poly(sodium 4‐styrenesulfonate) (PANI‐PSS) and cationic poly(diallydimethylammonium chloride) (PDADMAC). Anionic polyaniline was prepared by the interfacial polymerization of aniline monomer in the presence of PSS which acted as template to provide water solubility. The PSS to PANI concentration ratios used in the synthesis step was found to have a major effect on the final PANI‐PSS synthesis, its self assembly and the electrical properties of the prepared films. The optical and electrical properties of the films were measured by ultraviolet‐visible spectroscopy (UV‐Vis) and a 4‐point probe setup, respectively while the thickness of the films was measured by atomic force microscopy (AFM). Results showed that the optimum condition for the film growth and optimal conductivity were obtained with different synthesis conditions. These results suggest that the PSS concentration used for interfacial synthesis of PANI must be finely tuned depending on the type of application aimed by the user. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Layer-by-layer deposition of green synthesised silver nanoparticles on polyester air filters and its antimicrobial activity

Silver nanoparticles stabilised with anionic polymeric polyelectrolytes were successfully synthesised by high-energy UV reduction. Three types of polyelectrolytes were used including poly(methacrylic acid) (PMA), poly(acrylic acid) (PAA) and poly(4-styrenesulphonic acid-co-maleic acid) (CoPSS). The formation of the prepared solutions exhibited surface plasmon resonance at the wavelength of 475, 730 and 408 nm by using PMA, PAA and CoPSS as the stabilising agents. UV–visible spectrophotometer, transmission electron microscope (TEM) and zeta potential analyser were employed to characterise the formation of the prepared solutions. The silver nanoparticles stabilised with anionic polyelectrolytes were immobilised on polyester air filters using a layer-by-layer technique. This is the sequential dipping of polyester air filters in a dilute solution of cationic poly(diallyldimethylammonium chloride) and anionic polymeric polyelectrolytes capped silver. The surface topography of the polyester air filters were measured by field emission scanning electron microscope. Results showed that silver nanoparticles had the highest surface coverage on the polyester air filters probably because it is a good bonding candidate and insures strong film growth. The multilayers polyester air filters coated silver nanoparticles were tested against the gram positive pathogen Staphylococcus aureus. The deposition of silver nanoparticles onto the polyester air filters resulted in 92.18%, 84.32% and 71.19% of bacteria removal using PMA, PAA and CoPSS as the stabilising agent.     

Optimization on Pretreatment and Enzymatic Hydrolysis of Sugarcane Trash for Ethanol Production

The present study was conducted for the optimization of pretreatment and enzymatic hydrolysis of lignocellulosic biomass （sugarcane trash）, which is a renewable resource for the production of bioethanol. The pretreatment and enzymatic hydrolysis conditions including alkali （NaOH）/dilute acid （H2SO4）, substrate and chemical concentration for pretreatment, enzyme dosage, pH, temperature and substrate concentration for hydrolysis were varied and evaluated for sugar and ethanol production at the end. The optimum condition was accomplished using 15% w/v DS of 0-2 mm sugarcane trash in size of particle. It was pretreated with two steps of 2% w/v NaOH autoclaving followed by 2% w/v H2SO4 autoclaving with washing step after pretreatment. An enzymatic hydrolysis was then performed using 15% w/v DS pretreated substrate, hydrolyzed with cellulase 50 filter paper unit （FPU）/g DS at 50 ℃ and pH 5. After incubating at 160 r for 48 h, 117.16 g/L reducing sugar was obtained. The achieved sugar after enzymatic hydrolysis was finally fermented to ethanol by Saccharomyces cerevisiae TISTR 5596, with concentration of 48.17 g/L ethanol or yield 0.509 g/g reducing sugars which was equal to 99.81% of theoretical yield.