Effective Elimination of Contaminant Antibiotics Using High-Surface-Area Magnetic-Functionalized Graphene Nanocomposites Developed from Plastic Waste.

The presence of pharmaceutical residues in aquatic environments represents a risk for the equilibrium of the ecosystem and may seriously affect human safety itself in the long term. To address this issue, we have synthesized functional materials based on highly-reduced graphene oxide (HRGO), sulfonated graphene (SG), and magnetic sulfonated graphene (MSG). The method of synthesis adopted is simple and inexpensive and makes use of plastic bottle waste as the raw material. We have tested the fabricated materials for their adsorption efficiency against two model antibiotics in aqueous solutions, namely Garamycin and Ampicillin. Our tests involved the optimization of different experimental parameters of the adsorption process, such as starting antibiotic concentration, amount of adsorbent, and time. Finally, we characterized the effect of the antibiotic adsorption process on common living organisms, namely Escherichia coli DH5α (E. coli DH5α) bacteria. The results obtained demonstrate the efficiency of the method in addressing the issue of the emergence of antibiotic-resistant bacteria, which will help in preventing changes in the ecosystem.

Fabrication of a novel low-cost superoleophilic nonanyl chitosan-poly (butyl acrylate) grafted copolymer for the adsorptive removal of crude oil spills.

A novel superoleophilic-hydrophobic nonanyl chitosan-poly (butyl acrylate) grafted copolymer was fabricated as a low-cost oil-adsorbent. Chitosan (CS) was coupled with a hydrophobic nonanal (N) to form nonanyl chitosan (NCS) schiff base, and followed by grafting with butyl acrylate monomers (ButA). The grafted copolymer was characterized by FTIR, TGA and SEM tools. The grafting percent was augmented and reached 88.5% with increasing ButA concentration up to 156 mM. Moreover, measurements of contact angle proved the superoleophilic character of NCS-g-poly (ButA) copolymer with an oil-contact angle 31°. Factors affecting the removal process such as contact time, oil type, oil dose, adsorbent dose, temperature and agitation speed were optimized. An increment in the oil removal (%) was observed with increasing the oil viscosity in the order of gasoil < mobil-1 oil < light crude oil < heavy crude oil. Besides, the adsorption process followed the pseudo-second order model and the equilibrium data were sufficiently fitted with the Langmuir model with a maximum adsorption capacity 108.79 g/g at 25 °C. Thermodynamic parameters computed from Van't Hoff plot confirmed the process to be exothermic, favorable and spontaneous. The results nominate the superoleophilic adsorbent as a potential oil- adsorbent for petroleum oil spills removal.

Fabrication of biodegradable gelatin/chitosan/cinnamaldehyde crosslinked membranes for antibacterial wound dressing applications.

This study intends to fabricate new biodegradable and antimicrobial membranes based on crosslinked gelatin/chitosan biopolymers. Cinnamaldehyde was incorporated into membranes for boosting their antimicrobial activities. FTIR spectroscopy and electronic spectrum analysis were used to prove their chemical structures, while SEM and TGA analysis were applied to investigate the morphological changes and the thermal properties of the crosslinked membranes. Moreover, ion exchange capacity, wettability and mechanical analysis were also conducted to get more information about the physicochemical properties for the developed membranes. Four different types of bacteria have been used for studying the antibacterial activities of the crosslinked membranes (one gram-positive and three gram-negative bacteria). The results showed a significant augmentation in the inhibition percent with increasing cinnamaldehyde content in the membrane matrix. Besides, hemocompatibility, biodegradability, and cytotoxicity studies were performed and the findings emphasized that the as-fabricated biodegradable gelatin/chitosan/cinnamaldehyde membranes could be efficiently used as antibacterial dressers for ameliorating the wound healing.

Affinity covalent immobilization of glucoamylase onto ρ-benzoquinone-activated alginate beads: II. Enzyme immobilization and characterization.

A novel affinity covalent immobilization technique of glucoamylase enzyme onto ρ-benzoquinone-activated alginate beads was presented and compared with traditional entrapment one. Factors affecting the immobilization process such as enzyme concentration, alginate concentration, calcium chloride concentration, cross-linking time, and temperature were studied. No shift in the optimum temperature and pH of immobilized enzymes was observed. In addition, K (m) values of free and entrapped glucoamylase were found to be almost identical, while the covalently immobilized enzyme shows the lowest affinity for substrate. In accordance, V (m) value of covalently immobilized enzyme was found lowest among free and immobilized counter parts. On the other hand, the retained activity of covalently immobilized glucoamylase has been improved and was found higher than that of entrapped one. Finally, the industrial applicability of covalently immobilized glucoamylase has been investigated through monitoring both shelf and operational stability characters. The covalently immobilized enzyme kept its activity over 36 days of shelf storage and after 30 repeated use runs. Drying the catalytic beads greatly reduced its activity in the beginning but recovered its lost part during use. In general, the newly developed affinity covalent immobilization technique of glucoamylase onto ρ-benzoquinone-activated alginate carrier is simple yet effective and could be used for the immobilization of some other enzymes especially amylases.