Innovative green/non-toxic Bi2S3@g-C3N4 nanosheets for dark antimicrobial activity and photocatalytic depollution: Turnover assessment.

Herein, green and non-toxic bismuth sulphide@graphitic carbon nitride (Bi2S3@g-C3N4) nanosheets (NCs) were firstly synthesized by ultrasonicated-assisted method and characterized with different tool. Bi2S3@g-C3N4 NCs antimicrobial activity tested against three types of microbes. As well the heterostructured Bi2S3@g-C3N4 NCs was investigated for removing dye and hexavalent chromium under visible light and showed high efficiency of photocatalytic oxidation/reduction higher than g-C3N4 alone, attributing to lower recombination photogenerated electron-hole pairs. Bi2S3@g-C3N4 NCs showed high antimicrobial efficiencies against Staphylococcus aureus (S. aureus) as a Gram positive bacterium, Escherichia coli (E. Coli)as a Gram negative bacterium and Candida albicans (C. albicans) and that the disinfection rates are 99.97%, 99.98% and 99.92%, respectively. The core mechanism is that the bacterial membrane could be destroyed by reactive oxygen species. The Bi2S3@g-C3N4 NCs is promising for environmental disinfection including water and public facilities disinfection and solar photocatalytic depollution. Turnover number (TON) and Turnover frequency (TOF) are used as concise assessment indicator for photocatalytic efficiency.

Application of nanometal oxides in situ in nonwoven polyester fabric for the removal of bacterial indicators of pollution from wastewater.

The objective of this study is to investigate and assess the use of in situ deposit nanosilver (nAg2O) or nanocopper oxides (nCuO) into nonwoven polyester fabric (NWPF) as a safe and effective antibacterial filter of pollution from domestic wastewater. The bactericidal effect of both nAg2O and nCuO was examined against Gram-negative bacteria (Escherichia coli, Salmonella typhi) and Gram-positive bacteria (Enterococcus faecalis, Staphylococcus aureus) using agar diffusion disk method. In addition, the capability of nAg2O and nCuO as disinfectants for secondary treated domestic wastewater was investigated as a case study. Transmission electron microscope (TEM) confirmed the formation of nAg2O and nCuO particles with average particle sizes of 15 and 41 nm, respectively. Disk diffusion results showed that nAg2O had a higher bactericidal effect than nCuO. Moreover, the disinfection of secondary treated wastewater using 1.27 mg/cm(3) of nAg2O in the nonwoven fabric was capable of hindering 99.6% and 91.7% of total and fecal coliforms within 10 minutes with a residual value of 18 and 15 MPN-index/100 mL, respectively. The residual total and fecal coliform concentrations were far less than that stated in the national and international limits for wastewater reuse in agriculture purpose.

Assessment of toxicity and antimicrobial performance of polymeric inorganic coagulant and evaluation for eutrophication reduction.

In this study, the efficacy of the promising iron-based polymeric inorganic coagulant (POFC) was assessed for the reduction of eutrophication effect (freshwater toxicity) and the microbial loads from wastewater. Toxicity assessment for POFC was conducted on mice and skin cell lines. The results confirm the lower toxicity level of POFC. The POFC showed excellent antibacterial efficacy against Gram-positive and Gram-negative bacteria. Moreover, it demonstrated a remarkable effectiveness against black fungus such as Aspergillus niger and Rhizopus oryzae. Additionally, POFC showed antiviral effectiveness against the highly pathogenic H5N1 influenza virus as well as Middle East respiratory syndrome coronavirus (MERS-CoV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). POFC-based treatment gives excellent removal percentages for phosphate, and phosphorus at doses below 60 ppm with a low produced sludge volume that leads to 84% decrease in the rate of eutrophication and freshwater toxicity. At a POFC concentration of 60 ppm, remarkable reduction rates for total coliforms, fecal coliforms, and E. coli were achieved. After POFC-based coagulation, the produced sludge retains a lower bacterial density due to the antibacterial activity of POFC. Furthermore, it revealed that the observed removal efficiencies for fungi and yeasts in the produced sludge reached 85% at a POFC dose of 60 ppm. Overall, our research indicates that POFC has potential for application in pre-treatment of wastewater and serves as an antimicrobial agent.

Sustainable grafted chitosan-dialdehyde cellulose with high adsorption capacity of heavy metal.

A novel adsorbent was prepared using a backbone comprising chemically hybridized dialdehyde cellulose (DAC) with chitosan via Schiff base reaction, followed by graft copolymerization of acrylic acid. Fourier transform infrared spectroscopy (FTIR) confirmed the hybridization while scanning electron microscopy (SEM) revealed intensive covering of chitosan onto the surface of DAC. At the same time, energy dispersive X-ray (EDX) proved the emergence of nitrogen derived from chitosan. The X-ray diffraction (XRD) indicated that the crystallinity of the backbone and graft copolymer structures was neither affected post the hybridization nor the grafting polymerization. The adsorbent showed high swelling capacity (872%) and highly efficient removal and selectivity of Ni2+ in the presence of other disturbing ions such as Pb2+ or Cu2+. The kinetic study found that the second-order kinetic model could better describe the adsorption process of (Cu2+, Ni2+) on the graft copolymer. In contrast, the first-order kinetic model prevails for the binary mixture (Pb2+, Ni2+). Moreover, the correlation coefficient values for the adsorption process of these binary elements using Langmuir and Freundlich isotherms confirmed that the developed grafted DAC/chitosan exhibits a good fit with both isotherm models, which indicates its broadened and complicated structure. Furthermore, the grafted DAC/chitosan exhibited high efficient regeneration and high adsorption capacity for Pb2+, Cu2+ and Ni2+.

Green Route for the Removal of Pb from Aquatic Environment.

AIM AND OBJECTIVE: Wastewater treatment/remediation is a very important process that has a great environmental and economic impact. Therefore, it is crucial to innovate different methods to remove pollutants of different sources from wastewater. This work was conducted in order to study the removal of lead (Pb+2) from wastewater using microspheres of composites of sodium alginate, cellulose and chitosan, as well as using a cost-effective green route through composites of sodium alginate and dried water hyacinth. MATERIALS AND METHODS: Molecular modeling at B3LYP/6-31g(d,p) was utilized to study sodium alginate, cellulose and chitosan. Sodium alginate was cross-linked with calcium chloride to form microspheres, then both sodium alginate/cellulose and sodium alginate/chitosan were also crosslinked as 50/50 to form microspheres. The roots of the aquatic plant water hyacinth in dry form were added to the cross-linked sodium alginate for up to 70%. SEM and FTIR were employed to study the surface of the prepared microspheres and their structures respectively. Atomic absorption spectroscopy was used to study the levels of Pb. RESULTS: Molecular modeling indicated that the blending of such structures enhances their ability to bind with surrounding molecules owing to their ability to form hydrogen bonds. SEM results indicated that homogeneous structures of cellulose and chitosan are deformed when blended with sodium alginate, and FTIR confirmed the proper formation of the desired blends. Microspheres from sodium alginate showed the ability to remove Pb+2 from wastewater. SEM indicated further deformation in the morphology with the roughness of sodium alginate/water hyacinth microspheres, while FTIR confirmed the uniform matrices of the microspheres. The removal of Pb+2 was enhanced because of the addition of dried water hyacinth's roots. CONCLUSION: Modeling, experimental and kinetic data highlight sodium alginate/water hyacinth root as a green route to remediate Pb+2 from wastewater.

Low temperature-calcined TiO2 for visible light assisted decontamination of 4-nitrophenol and hexavalent chromium from wastewater.

In the present study, alkaline hydrothermally treated titania nanoparticles (TiO2-HT) are prepared and followed by calcination at different low temperatures to improve TiO2 activity under visible light. The prepared photocatalysts (PCs) are characterized by different tools. TiO2-HT is scrutinized for decontamination of para-nitrophenol (PNP) and hexavalent chromium ions (Cr6+ ions) under simulated sunlight. TiO2-HT-300 and TiO2-HT-400 PCs have nanosized particle with large surface area of 148 and 116.26 m2/g, respectively. Additionally, XRD and FTIR proved formation of nanocrystalline anatase TiO2. The different calcined TiO2-HT materials show lower adsorption capacity for PNP and Cr6+ ions. TiO2-HT-300 and HT-TiO2-400 PCs have higher reduction rate of PNP than that of uncalcined temperature titania (HT-TiO2-U) powder. Complete conversion of PNP is achieved at natural pH after 180 min over TiO2-HT-300. As well, TiO2-HT-300 exhibits a superior photocatalytic removal of Cr6+ ions. The enhanced photocatalytic efficacy is ascribed to the synergism between higher surface area and particle size (quantum effect) of TiO2-HT-300. As results, HO· radicals are the main key active species for the photocatalytic degradation of PNP over TiO2- HT-300 PC but contribution of O2- and h+ holes is minor. The used method for preparation of TiO2-HT-300 reduces the cost preparation as well as environmental impact reduction. Finally, low temperature-calcined TiO2 is promising visible light active and an efficient photocatalyst with lower environmental impact for detoxification of PNP and Cr6+ ions from water.

Grafting polymerization of acrylic acid onto chitosan-cellulose hybrid and application of the graft as highly efficient ligand for elimination of water hardness: Validation of high selectivity in presence of interfering ions.

Graft Copolymer resulting from polymerization of acrylic acid from chitosan is non-coherent, brittle and exhibit modest swelling in water, which limits its application. Chitosan-cellulose hybrid was initially prepared and novel polymeric ligand ((CTS/Cell)-g-PAA) derived from grafting polymerization of acrylic acid from this hybrid was fabricated and investigated using fourier transform infrared (FTIR) and Scanning electron microscopy (SEM). Also, the graft copolymer exhibited high mass transfer under a wide range of pH values due to its elevated hydrophilicity in addition to a good mechanical strength with respect to the comparable graft derived from chitosan as sole backbone for the grafting. The high content of different oxygen and nitrogen-containing groups in a crowded chemical atmosphere along with the high swelling qualified the graft to act as very efficient polymeric ligand with high capacity of removal of metal ions from water under broad conditions. The polymeric ligand performed outstandingly and competitively in the removal of water hardness even in presence of other interfering ions.

The promise of a specially-designed graft copolymer of acrylic acid onto cellulose as selective sorbent for heavy metal ions.

A specially-designed graft copolymer of acrylic acid onto in-situ formed cellulose-fulvate hybrid showed privileged tendency for uptake of Pb(II) during competitive removal from a mixture containing Cd(II) and Ni(II) within 5min at pH 5. This novel trend is attributed mainly to the crowded high content of coordinating centers within the designed graft copolymer along with the acquired superabsorbency. This provides an outstanding tool to separate some metal ions selectively from mixtures containing multiple ions on kinetic basis. Thus, the designed graft copolymer structure exhibited superior efficiency that reached ∼95% for sole removal of Pb(II). Kinetic modeling for Pb(II) individual removal showed excellent fitting with a pseudo second-order model. Intraparticle diffusion model on the other hand ensured governance of boundary layer effect over diffusion during the removal process due to the superabsorbency feature of the graft copolymer. The experimental findings were described with models such as Freundlich, Langmuir, and Dubinin-Radushkevich. The Langmuir and Freundlich models showed convenience with the adsorption isotherm of Pb(II) onto the developed graft copolymer.

Potassium fulvate-modified graft copolymer of acrylic acid onto cellulose as efficient chelating polymeric sorbent.

Acrylic acid (AA) was graft copolymerized from cellulose (Cell) in presence of potassium fulvate (KF) in order to enhance the chemical activity of the resulting chelating polymer and the handling as well. Fourier transform infrared (FTIR) proved that KF was efficiently inserted and became a permanent part of the network structure of the sorbent in parallel during the grafting copolymerization. Scanning electron microscopy (SEM) revealed intact homogeneous structure with uniform surface. This indicates improvement of the handling, however, it was not the case for the graft copolymer of acrylic acid onto cellulose in absence of KF, which is known to be brittle and lacks mechanical integrity. Effective insertion of this co-interpenetrating agent provided more functional groups, such as OH and COOH, which improved the chelating power of the produced sorbent as found for the removal of Cu2+ ions from its aqueous solutions (the removal efficiency reached ∼98.9%). Different models were used to express the experimental data. The results corroborated conformity of the pseudo-second order kinetic model and Langmuir isotherm model to the sorption process, which translates into dominance of the chemisorption. Regeneration of the chelating polymers under harsh conditions did not affect the efficiency of copper ions uptake up to three successive cycles. A thermodynamic investigation ensured exothermic nature of the adsorption process that became less favourable at higher temperatures.

Graft copolymerization of cellulose acetate for removal and recovery of lead ions from wastewater.

In this study, cellulose acetate (CA) was modified by grafting with an equimolar binary mixture of acrylic acid (AA) and acrylamide (AAm) via radical polymerization technique using benzoyl peroxide as an initiator. Comparative studies between CA powder and modified CA [CA-g-(AA-co-AAm)] were investigated for Pb(II) ions removal and recovery from wastewater. The main operating conditions such as pH, concentration of Pb(II) ions and sorbent dose were also studied. Kinetic modeling has been studied and lead uptake capacity was calculated using the Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich (DKR) models. The maximum sorption capacity (qemax) for Pb ions was only 9.4 mg/g for unmodified CA, while, it was reached to 66.67 mg/g by using modified CA. Spectroscopic analysis (FTIR), SEM, EDX and XRD analysis were investigated for CA and modified CA before and after recovery of lead ions from wastewater.

A novel structure for removal of pollutants from wastewater.

Dried water hyacinth was subjected to molecular modifications using quantum mechanical calculations. The model simulates the modified plant as 3 cellulose units, one lignin and some metal oxides namely CaO; FeO and Al(OH)3 are attached through O-Linkage. The model suggests the ability to remove inorganic pollutants from wastewater according to unique hydrogen bonding and high total dipole moment. Based on this model microspheres are synthesized in the laboratory from dried water hyacinth and chitosan following self-assembly method. FTIR spectrum of microspheres exhibits only the characteristic bands for raw materials which give strong evidence that the formed material is a composite. The analysis of SEM micrographes of microspheres showed that the fibers of water hyacinth are imbedded in the crosslinked chitosan matrix. Batch adsorption kinetic models revealed that the sorption of lead ions on microsphere was very fast and the equilibrium was rapidly attained within 30 min. and properly correlated with the second-order kinetic model. Different models of isotherm sorption were used to describe the Pb (II) adsorption onto microspheres. From Langmuir isotherm, the maximum adsorption capacity (q(max)) for Pb(II) was 312.5 mg/g, which is about 3 times higher than that of the crude hyacinth. The free energy (E) was 15.798 kJ/mol which shows that the sorption process is endothermic and the mechanism of reaction is an ion-exchange. Even after four cycles of adsorption-desorption, the adsorption capacity was maintained and the decline in efficiency was less than 10%.

Removal of Cd(II) and Pb(II) from aqueous solution using dried water hyacinth as a biosorbent.

Possible usages of dried water hyacinth as biosorbent for metal ions were investigated. A model describing the plant is presented on density functional theory DFT and verified experimentally with FTIR. The model shows that water hyacinth is a mixture of cellulose and lignin. Dried shoot and root were found as good sorbent for Cd(II) and Pb(II) at optimum dosage of 5.0 g/l and pH 5.0; equilibrium time was attained within 30-60 min. The removal using root and shoot were nearly equal and reached more than 75% for Cd and more than 90% for Pb. Finally the second-order kinetics was the applicable model. Hydrogen bonds of reactive functional groups like COOH play the key role in the removal process.

Spectroscopic analyses of pollutants in water, sediment and fish.

Water ways in Egypt is suffering from continual discharge without adequate treatment especially in the Delta and greater Cairo area. Accordingly water, sediments and catfishes were collected from El Mouheet El Youmna drain in Giza. Cd, Cr, Pb and Zn were determined furthermore the molecular structure of sediment and catfish were conducted with FTIR spectroscopy. Although studied metals were lower in water, higher values are recorded in sediment and catfish samples. FTIR shows possible interaction among metals and organic structures mainly proteins. The bioaccumulation of Pb and Cd proportion was significantly increased in the liver tissues of catfish. A correlation coefficient among sediment and fish liver metals accumulation exist. This infers that the waste assimilation capacity for the drain is high, a phenomena that could be ascribed to dilution, sedimentation and continual water exchange. Furthermore, the genotoxicity affect in catfish genomic corroborates the genus diagnostic markers which attributed to long pollution. This is an indication that agriculture and industrial wastes discharged into the drain has badly a significant effect on the ecological balance.

Application of zeolite prepared from Egyptian kaolin for the removal of heavy metals: II. Isotherm models.

In this study, the adsorption behavior of zeolites A and X, which are prepared from very cheap local Egyptian clay (kaolin), with respect to Cu(2+), Cd(+2), Cr(+2), Ni(+2) and Zn(2+) has been studied. The batch method has been employed, using metal solutions ranging from 100 to 400 mg/L. The distribution coefficients (K(d)) and adsorption percent were determined for the adsorption system as a function of sorbate concentration. In the uptake evaluation part of the study, adsorption ratios of metal cations on zeolites A and X match to Langmuir, Freundlich, and Dubinin-Kaganer-Radushkevich (DKR) adsorption isotherm data. Also, every cation exchange capacity for metals has been calculated. According to the equilibrium studies, the selectivity sequence can be given as Pb(2+)>Cd(2+)>Cu(2+)>Zn(2+)>Ni(2+). It was found that the uptake depend on hydrated ion diameter. This study may attract more interest due to the presence of large reservoirs of very cheap kaolin in Egypt from which both zeolite types were prepared.

Distribution and bacterial bioavailability of selected metals in sediments of Ismailia Canal, Egypt.

The spatial and temporal variability in concentrations of heavy metals, and the portion of the bioavailable metals for bacterial community of Ismailia Canal sediment were conducted. Furthermore, Fourier Transform Infrared Spectroscopy (FTIR) was employed to elucidate the molecular structure of the same sediment samples. Results indicate that Cu, Cr and Zn concentrations showed temporal variation (pPb>Cu>Cr>Co. Also, the shift in the CO suggested that hydrated divalent metals are interacting with organic acids to form hexahydrated metals carboxylate. There were non-significant interactions between temporal and spatial variation for all the studied metals.