Fast microwave-assisted sorption of heavy metals on the surface of nanosilica-functionalized-glycine and reduced glutathione

Characterization, antibacterial, and cytotoxic activities of silver nanoparticles using the whole biofilm layer as a macromolecule in biosynthesis

Recently, multi-drug resistant (MDR) bacteria are responsible for a large number of infectious diseases that can be life-threatening. Globally, new approaches are targeted to solve this essential issue. This study aims to discover novel antibiotic alternatives by using the whole components of the biofilm layer as a macromolecule to synthesize silver nanoparticles (AgNPs) as a promising agent against MDR. In particular, the biosynthesized biofilm-AgNPs were characterized using UV-Vis spectroscopy, electron microscopes, Energy Dispersive X-ray (EDX), zeta sizer and potential while their effect on bacterial strains and normal cell lines was identified. Accordingly, biofilm-AgNPs have a lavender-colored solution, spherical shape, with a size range of 20-60 nm. Notably, they have inhibitory effects when used on various bacterial strains with concentrations ranging between 12.5 and 25 µg/mL. In addition, they have an effective synergistic effect when combined with phage ZCSE9 to inhibit and kill Salmonella enterica with a concentration of 3.1 µg/mL. In conclusion, this work presents a novel biosynthesis preparation of AgNPs using biofilm for antibacterial purposes to reduce the possible toxicity by reducing the MICs using phage ZCSE9.

A novel insight into the microwave induced catalytic reduction mechanism in aqueous Cr(VI) removal over ZnFe2O4 catalyst

Aqueous Cr(VI) pollution is an emerging environmental issue. Herein, a sphere-like ZnFe₂O₄ catalyst with a size of ∼430 nm was prepared by a solvothermal method, by which the aqueous Cr(VI) in a 50 mL solution with concentration of 50 mg/L was completely removed after 10 min-microwave (MW) irradiation. "Surface temperature visualization" tests and COMSOL simulations showed that the surface temperature of the as-prepared ZnFe₂O₄ catalysts could be as high as > 1000 °C only after 300 s MW irradiation, and the work function calculations and scavenging experiments demonstrated that the excited electrons derived by the "hot spots" effect of the ZnFe₂O₄ catalysts reduced the Cr(VI) to Cr(III). Kinetic reaction process of the reduction of *Cr₂O₇^2- to *CrO₃H₃ over the ZnFe₂O₄ catalysts was clarified by using DFT calculation, and the results indicated that *Cr₂O₇^2- adsorbed on the Fe atoms was more easily to be reduced, and that Fe atoms played more significant roles than the Zn and O atoms in ZnFe₂O₄ catalysts. The present study not only proves that the MW induced ZnFe₂O₄ catalytic reduction was promising for ultrafast remediation of toxic Cr(VI), but also provides a new insight into the corresponding mechanism.

Technological trends in nanosilica synthesis and utilization in advanced treatment of water and wastewater

Water and wastewater treatment applications stand to benefit immensely from the design and development of new materials based on silica nanoparticles and their derivatives. Nanosilica possesses unique properties, including low toxicity, chemical inertness, and excellent biocompatibility, and can be developed from a variety of sustainable precursor materials. Herein, we provide an account of the recent advances in the synthesis and utilization of nanosilica for wastewater treatment. This review covers key physicochemical aspects of several nanosilica materials and a variety of nanotechnology-enabled wastewater treatment techniques such as adsorption, separation membranes, and antimicrobial applications. It also discusses the prospective design and tuning options for nanosilica production, such as size control, morphological tuning, and surface functionalization. Informative discussions on nanosilica production from agricultural wastes have been offered, with a focus on the synthesis methodologies and pretreatment requirements for biomass precursors. The characterization of the different physicochemical features of nanosilica materials using critical surface analysis methods is discussed. Bio-hybrid nanosilica materials have also been highlighted to emphasize the critical relevance of environmental sustainability in wastewater treatment. To guarantee the thoroughness of the review, insights into nanosilica regeneration and reuse are provided. Overall, it is envisaged that this work's insights and views will inspire unique and efficient nanosilica material design and development with robust properties for water and wastewater treatment applications.

Microwave enhanced sorption of methylene blue dye onto bio-synthesized iron oxide nanoparticles: kinetics, isotherms, and thermodynamics studies

To adequately address the grave human health risks and environmental damage caused by the uncontrolled utilization of organic dyes, we greenly synthesized iron oxide nanoparticles (IONPs) using Spirulina platensis micro-algae for sequestration of cationic methylene blue (MB) dye from an aqueous solution. The nano-engineered sorbent was thoroughly scrutinized by different spectral analyses of; FT-IR, SEM, EDX, BET surface area, TEM, VSM, UV/Vis spectroscopy, and PH_PZC measurement. The adsorption of MB was methodically carried out in a batch process to investigate the effects of initial pH (2.2-10.4), adsorbent concentration (0.5-5.0 g L^-1), initial dye concentration (10-1000 mg L^-1), contact time (0-230 min), and adsorption temperature (298 K, 308 K, 318 K, and 328 K). The outlined results inferred that the maximum adsorption capacity of MB dye by IONPs (surface area of 134.003 m²/g, a total pore volume of 0.3715 cc/g, and average pore size of 5.54 nm) was 312.5 mg g^-1 under the optimized pH value (i.e., pH = 10.4). Collectively, the adsorption kinetics profile showed that the experimental data were in good agreement with the PSORE model, and the equilibrium adsorption isotherm data were quantitatively dominated by the Langmuir model. The thermodynamic findings conformed to the endothermic nature of the adsorption process. Interestingly, the proposed microwave scenario enhanced the adsorption rate and the equilibrium was attained in a very short time (only 1 min), compared with the normal sorption conditions (∼70 min). Repeatability of the spent sorbent was successfully emphasized for 5 times of adsorption/desorption cycles using 0.5 M of HCl. The productive adsorbent admirably sequestered MB dye from spiked real specimens (>83%). These results demonstrated that IONPs can be considered as a cost-efficient adsorbent in practical applications such as wastewater purification.

Al-Omar M. Synthesis and Characterization of CuFe2O4 Nanoparticles Modified with Polythiophene: Applications to Mercuric Ions Removal

In this research, CuFe₂O₄ nanoparticles were synthesized by co-precipitation methods and modified by coating with thiophene for removal of Hg(II) ions from aqueous solution. CuFe₂O₄ nanoparticles, with and without thiophene, were characterized by x-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), energy dispersive x-ray (EDX), high-resolution transmission electron microscopy (HRTEM) and Brunauer-Emmett-Teller (BET). Contact time, adsorbent dose, solution pH, adsorption kinetics, adsorption isotherm and recyclability were studied. The maximum adsorption capacity towards Hg²⁺ ions was 7.53 and 208.77 mg/g for CuFe₂O₄ and CuFe₂O₄@Polythiophene composite, respectively. Modification of CuFe₂O₄ nanoparticles with thiophene revealed an enhanced adsorption towards Hg²⁺ removal more than CuFe₂O₄ nanoparticles. The promising adsorption performance of Hg²⁺ ions by CuFe₂O₄@Polythiophene composite generates from soft acid-soft base strong interaction between sulfur group of thiophene and Hg(II) ions. Furthermore, CuFe₂O₄@Polythiophene composite has both high stability and reusability due to its removal efficiency, has no significant decrease after five adsorption-desorption cycles and can be easily removed from aqueous solution by external magnetic field after adsorption experiments took place. Therefore, CuFe₂O₄@Polythiophene composite is applicable for removal Hg(II) ions from aqueous solution and may be suitable for removal other heavy metals.

Fate of environmental pollutants

This annual review covers the literature published in 2018 on topics related to the occurrence and fate of environmental pollutants in wastewater. Due to the vast amount of literature published on this topic, we have discussed only a portion of the quality research publications, due to the limitation of space. The abstract search was carried out using Web of Science, and the abstracts were selected based on their relevance. In a few cases, full-text articles were referred to understand new findings better. This review is divided into the following sections: antibiotic-resistant bacteria (ARBs) and antibiotic-resistant genes (ARGs), disinfection by-products (DBPs), drugs of abuse (DoAs), estrogens, heavy metals, microplastics, per- and polyfluoroalkyl compounds (PFAS), pesticides, and pharmaceuticals and personal care products (PPCPs), with the addition of two new classes of pollutants to previous years (DoAs and PFAS).

Microwave-accelerated sorption of cationic dyes onto green marine algal biomass

Monolithic algal green powder (MAGP) was fabricated based on the marine green macroalga Enteromorpha flexuosa. It was scrutinized by using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), Fourier transform infrared (FT-IR), point of zero charge (PH_PZC), and Brunauer-Emmett-Teller (BET) surface area. The ability of Enteromorpha flexuosa to capture both crystal violet (CV) and methylene blue (MB) from aqueous solutions was evaluated. The influence of variable conditional parameters on CV dye and MB dye batch sorption was investigated. Results showed that percentage removal of 90.3% and 93.4% were obtained under optimum conditions of variables for CV and MB, respectively. Effect of microwave radiation on dye sorption was also appraised. Processing the sorption under microwave irradiation (microwave-enforced sorption, MES) increases mass transfer and a contact time as low as 1 min is sufficient under optimized conditions (exposure time and power) reaching the equilibrium. The reusability of MAGP sorbent was achieved for four cycles of sorption/desorption by using 0.5 M HCl. The ability of MAGP for cationic dyes removal from spiked tap water and petrochemical plant discharge wastewater samples was successfully registered. Ultimately, the displayed data showed a superior and excellent ability of algal powder to be exploited as a green, harmless, and effective sorbent for cationic dye removal.

Characteristics and performance of Cd, Ni, and Pb bio-adsorption using Callinectes sapidus biomass: real wastewater treatment

In the current study, the bio-adsorption potential of Callinectes sapidus biomass for control of cadmium, nickel, and lead from the aqueous stream was assessed. Spectrum analysis of FTIR, AFM, EDAX, mapping, SEM, TEM, and XRF was used to study the properties of the C. sapidus biomass. The XRF analysis revealed that C. sapidus bio-adsorbent has various effective metal oxides that can be useful to adsorb pollutants. The best model to describe the equilibrium data was Freundlich isotherm. The Langmuir bio-adsorption capacity was reported at 31.44 mg g^-1, 29.23 mg g^-1, and 29.15 mg g^-1 for lead, cadmium, and nickel ions, respectively. Pseudo-first-order and pseudo-second-order kinetic models were studied to test the kinetic behavior of the process. An intra-particle diffusion model was used to determine the effective mechanisms involved in the bio-adsorption. Based on t_1/2, it can be concluded that the equilibrium speed of the bio-adsorption process is high. The thermodynamic study showed that the metal bio-adsorption process using C. sapidus biomass is exothermic and spontaneous. The field applicability of the crab bio-adsorbent for eliminating concurrently several contaminants (metal ions, antibiotics, sulfate, nitrate, and ammonium) from an actual wastewater was successfully examined.

Thiol-/thioether-functionalized porous organic polymers for simultaneous removal of mercury(ii) ion and aromatic pollutants in water

Two novel thiol-/thioether-functionalized porous organic polymers were prepared for simultaneous removal of Hg(ii) and aromatic pollutants in water with high binding ability and fast uptake kinetics.