Hybrid Zinc Phthalocyanine/PVDF-HFP System for Reducing Biofouling in Water Desalination: DFT Theoretical and MolDock Investigations.

Fouling and biofouling remain significant challenges in seawater desalination plants. One practical approach to address these issues is to develop anti-biofouling membranes. Therefore, novel hybrid zinc phthalocyanine/polyvinylidene fluoride-co-hexafluoropropylene (Zn(4-PPOx)4Pc/PVDF-HFP) membranes were prepared by electrospinning to evaluate their properties against biofouling. The hybrid nanofiber membrane was characterized by atomic force microscopy (AFM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and contact angle measurements. The theoretical calculations of PVDF-HFP, Zn(4-PPOx)4Pc), and Zn(4-PPOx)4Pc/PVDF-HFP nanofibers were performed using a hybrid functional RB3LYP and the 6-31 G (d,p) basis set, employing Gaussian 09. DFT calculations illustrated that the calculated physical and electronic parameters ensured the feasibility of the interaction of PVDF-HFP with Zn(4-PPOx)4Pc via a halogen-hydrogen bond, resulting in a highly stable and remarkably reactive structure. Moreover, molecular electrostatic potential (MEP) maps were drawn to identify the reactive regions of the Zn(4-PPOx)4Pc and PVDF-HFP/Zn(4-PPOx)4Pc nanofibers. Molecular docking analysis revealed that Zn(4-PPOx)4Pc has highest binding affinity (-8.56 kcal/mol) with protein from S. aureus (1N67) mainly with ten amino acids (ASP405, LYS374, GLU446, ASN406, ALA441, TYR372, LYS371, TYR448, LYS374, and ALA442). These findings highlight the promising potential of Zn(4-PPOx) 4Pc/PVDF-HFP nanocomposite membranes in improving the efficiency of water desalination by reducing biofouling and providing antibacterial properties.

Resource recovery of food waste through continuous thermophilic in-vessel composting.

In the Kingdom of Saudi Arabia (KSA) and Gulf region, a very small amount of municipal solid waste (MSW) is treated for compost production. The produced compost through traditional methods of compost piles and trenches does not coincide with the international standards of compost quality. Therefore, in this study, a continuous thermophilic composting (CTC) method is introduced as a novel and efficient technique for treating food waste into a quality compost in a short period of time. The quality of the compost was examined by degradation rates of organic matter (OM), changes in total carbon (TC), ash contents, pH, dynamics in ammonium nitrogen (NH4-N) and nitrate nitrogen (NO3-N), and nitrification index (NI). The results showed that thermophilic treatment at 60 °C increased the pH of the substrate and promoted degradation and mineralization process. After 30 days of composting, the degree of OM degradation was increased by 43.26 and 19.66%, NH4-N by 65.22 and 25.23%, and NO3-N by 44.76 and 40.05% as compared to runs treated at 25 and 40 °C, respectively. The stability of the compost was attained after 30 to 45 days with quality better than the compost that was stabilized after 60 days of the experiment under mesophilic treatment (25 °C). The final compost also showed stability at room temperature, confirming the rapid degradation and maturation of food waste after thermophilic treatment. Moreover, the quality of produced compost is in line with the compost quality standard of United States (US), California, Germany, and Austria. Hence, CTC can be implemented as a novel method for rapid decomposition of food waste into a stable organic fertilizer in the given hot climatic conditions of KSA and other Gulf countries with a total net saving of around US $70.72 million per year.

A Highly Structured 1,10-Phenanthroline Arrayed Hydrophobic Sulfone Membrane Platform for the Rapid Determination and Speciation of Fe2+/Fe3+ Ions in Water.

An optical assay for the rapid determination and chemical speciation of Fe2+/Fe3+ species has been proposed for the first time on a polyether sulfone (PES) membrane platform. The small pore size and low wettability (θ ∼82°) of the membrane disallowed the dissipation of analyte droplets on the surface, thus localizing it onto nanoliter arrayed 1,10-phenanthroline spots. Under optimized conditions and within ∼5 min, an acceptable limit of detection (0.1 µg mL-1) and linear dynamic range (1 - 100 µg mL-1) were achieved. The proposed method was also successfully applied for indirect determination of Fe3+ ions in synthetic samples after reduction to Fe2+ using SO2. The performance of the proposed sensor was validated for its robustness and stability. Due to high selectivity and accuracy, the method was satisfactorily applied for the analysis of Fe2+/Fe3+ species in marine water samples. The proposed method is an easy and low-cost system coupled with good reproducibility and ruggedness, applicable for point-of-use testing.

Toxicity of iron oxide nanoparticles to grass litter decomposition in a sandy soil.

We examined time-dependent effect of iron oxide nanoparticles (IONPs) at a rate of 2000 mg kg-1 soil on Cynodon dactylon litter (3 g kg-1) decomposition in an arid sandy soil. Overall, heterotrophic cultivable bacterial and fungal colonies, and microbial biomass carbon were significantly decreased in litter-amended soil by the application of nanoparticles after 90 and 180 days of incubation. Time dependent effect of nanoparticles was significant for microbial biomass in litter-amended soil where nanoparticles decreased this variable from 27% after 90 days to 49% after 180 days. IONPs decreased CO2 emission by 28 and 30% from litter-amended soil after 90 and 180 days, respectively. These observations indicated that time-dependent effect was not significant on grass-litter carbon mineralization efficiency. Alternatively, nanoparticles application significantly reduced mineral nitrogen content in litter-amended soil in both time intervals. Therefore, nitrogen mineralization efficiency was decreased to 60% after 180 days compared to that after 90 days in nanoparticles grass-litter amended soil. These effects can be explained by the presence of labile Fe in microbial biomass after 180 days in nanoparticles amendment. Hence, our results suggest that toxicity of IONPs to soil functioning should consider before recommending their use in agro-ecosystems.

The role of hydrogen bonding in the fluorescence quenching of 2,6-bis((E)-2-(benzoxazol-2-yl)vinyl)naphthalene (BBVN) in methanol.

The excited state hydrogen bonding dynamics of BBVN in hydrogen donating methanol solvent was explored at the TD-BMK/cc-pVDZ level of theory with accounting for the bulk environment effects at the polarizable continuum model (PCM). The heteroatoms of the BBVN laser dye form hydrogen bonds with four methanol molecules. In the formed BBVN-(MeOH)4 complex, the A-type hydrogen bond (N…HO), of an average strength of 25kJmol-1, is twofold stronger than the B-type (O…HO) one. Upon photon absorption, the total HB binding energy increases from 78.5kJmol-1 in the ground state to 82.6kJmol-1 in the first singlet (S1) excited state. In consequence of the hydrogen bonding interaction, the absorption band maximum of the BBVN-(MeOH)4 complex, which was anticipated at 398nm (exp. 397), is redshifted by 5nm relative to that of the free dye in methanol. The spectral shift of the stretching vibrational mode for the hydrogen bonded hydroxyl groups (with a maximum shift of 285cm-1) from that of the free methanol indicated the elevated strengthening of hydrogen bonds in the excited state. The vibrational modes associated with hydrogen bonding provide effective accepting modes for the dissipation of the excitation energy, thus, decreasing the fluorescence quantum yield of BBVN in alcohols as compared to that in the polar aprotic solvents. Since there is no sign of photochemistry or phosphorescence, it seems reasonable in view of the outcomes of this study to assign the major decay process of the excited singlet (S1) of BBVN in alcohols to vibronically induced internal conversion (IC) facilitated by hydrogen bonding.

Zinc oxide nanoparticles affect carbon and nitrogen mineralization of Phoenix dactylifera leaf litter in a sandy soil.

We investigated the impact of zinc oxide nanoparticles (ZnO NPs; 1000mgkg-1 soil) on soil microbes and their associated soil functions such as date palm (Phoenix dactylifera) leaf litter (5gkg-1 soil) carbon and nitrogen mineralization in mesocosms containing sandy soil. Nanoparticles application in litter-amended soil significantly decreased the cultivable heterotrophic bacterial and fungal colony forming units (cfu) compared to only litter-amended soil. The decrease in cfu could be related to lower microbial biomass carbon in nanoparticles-litter amended soil. Likewise, ZnO NPs also reduced CO2 emission by 10% in aforementioned treatment but this was higher than control (soil only). Labile Zn was only detected in the microbial biomass of nanoparticles-litter applied soil indicating that microorganisms consumed this element from freely available nutrients in the soil. In this treatment, dissolved organic carbon and mineral nitrogen were 25 and 34% lower respectively compared to litter-amended soil. Such toxic effects of nanoparticles on litter decomposition resulted in 130 and 122% lower carbon and nitrogen mineralization efficiency respectively. Hence, our results entail that ZnO NPs are toxic to soil microbes and affect their function i.e., carbon and nitrogen mineralization of applied litter thus confirming their toxicity to microbial associated soil functions.

Hybrid chitosan/polyaniline-polypyrrole biomaterial for enhanced adsorption and antimicrobial activity.

In this work, chitosan (CS) functionalized polyaniline-polypyrrole (Pani-Ppy) copolymer (CS/Pani-Ppy) was synthesized applying a facile one pot method for the enhanced adsorption of Zn(II) and antimicrobial activity for E. coli and E. agglomerans. The synthesized materials were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform inferred spectroscopy and X-ray photoelectron spectroscopy. The adsorption of the Zn(II) on the synthesized materials was highly dependent on the pH of the solution, the initial metal ion concentration, and temperature. The adsorption of Zn(II) on the studied materials was as follows: CS/Pani-Ppy>Pani-Ppy>Ppy>Pani>CS. The results reveal that adsorption of Zn(II) follows the Langmuir adsorption isotherm, and that chemisorption occurs through pendant and bridging interactions, with active adsorbent sites. Thermodynamic results show the adsorption is spontaneous and exothermic in nature. The synthesized materials show excellent antimicrobial activity against E. coli and E. agglomerans bacterial organisms, and an approximately 100% decline in the viability of both strains was observed with CS/Pani-Ppy and Pani-Ppy. The order of antimicrobial activity for the synthesized materials was as follows: CS/Ppy-Pani>Ppy-Pani>Ppy>Pani>CS. The results show that the greater activity of CS/Ppy-Pani resulted from the electrostatic interaction between positively charged amine groups and negatively charged bacteria.

Bacteria and fungi can contribute to nutrients bioavailability and aggregate formation in degraded soils.

Intensive agricultural practices and cultivation of exhaustive crops has deteriorated soil fertility and its quality in agroecosystems. According to an estimate, such practices will convert 30% of the total world cultivated soil into degraded land by 2020. Soil structure and fertility loss are one of the main causes of soil degradation. They are also considered as a major threat to crop production and food security for future generations. Implementing safe and environmental friendly technology would be viable solution for achieving sustainable restoration of degraded soils. Bacterial and fungal inocula have a potential to reinstate the fertility of degraded land through various processes. These microorganisms increase the nutrient bioavailability through nitrogen fixation and mobilization of key nutrients (phosphorus, potassium and iron) to the crop plants while remediate soil structure by improving its aggregation and stability. Success rate of such inocula under field conditions depends on their antagonistic or synergistic interaction with indigenous microbes or their inoculation with organic fertilizers. Co-inoculation of bacteria and fungi with or without organic fertilizer are more beneficial for reinstating the soil fertility and organic matter content than single inoculum. Such factors are of great importance when considering bacteria and fungi inocula for restoration of degraded soils. The overview of presented mechanisms and interactions will help agriculturists in planning sustainable management strategy for reinstating the fertility of degraded soil and assist them in reducing the negative impact of artificial fertilizers on our environment.