Design of Bismuth Tungstate Bi2WO6 Photocatalyst for Enhanced and Environmentally Friendly Organic Pollutant Degradation.

In this study, a chemical precipitation approach was adopted to produce a photocatalyst based on bismuth tungstate Bi2WO6 for enhanced and environmentally friendly organic pollutant degradation. Various tools such as X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), optical spectroscopy and X-ray photoelectron spectroscopy, were employed to assess the structural and morphological properties. Hence, the XRD profiles showed a well crystallized Bi2WO6 orthorhombic phase. The photocatalytic performance of the resulting photocatalyst was assessed by the decomposition of Rhodamine B (RhB) and methyl orange (MO) with a decomposition efficiency of 97 and 92%, along with the highest chemical oxygen demand of 82 and 79% during 120 min of illumination, respectively. The principal novelty of the present work is to focus on the changes in the crystalline structure, the morphology, and the optical and the photoelectrochemical characteristics of the Bi2WO6, by tuning the annealing temperature of the designed photocatalyst. Such physicochemical property changes in the as-prepared photocatalyst will affect in turn its photocatalytic activity toward the organic pollutant decomposition. The photocatalytic mechanism was elaborated based on electrochemical impedance spectroscopy, photocurrent analysis, photoluminescence spectroscopy, and radical trapping measurements. The overall data indicate that the superoxide O2•- and holes h+ are the principal species responsible for the pollutant photodegradation.

Removal of cadmium and lead ions from aqueous solutions by novel dolomite-quartz@Fe3O4 nanocomposite fabricated as nanoadsorbent.

The elimination of heavy metal ion contaminants from residual waters is critical to protect humans and the environment. The natural clay (dolomite and quartz) based composite Fe3O4 nanoparticles (DQ@Fe3O4) has been largely explored for this purpose. Experimental variables such as temperature, pH, heavy metal concentration, DQ@Fe3O4 dose, and contact time were optimized in details. The DQ@Fe3O4 nanocomposite was found to achieve maximum removals of 95.02% for Pb2+ and 86.89% for Cd2+, at optimal conditions: pH = 8.5, adsorbent dose = 2.8 g L-1, the temperature = 25 °C, and contact time = 140 min, for 150 mg L-1 heavy metal ion initial concentration. The Co-precipitation of dolomite-quartz by Fe3O4 nanoparticles was evidenced by SEM-EDS, TEM, AFM, FTIR, XRD, and TGA analyses. Further, the comparison to the theoretical predictions, of the adsorption kinetics, and at the equilibrium, of the composite, revealed that they fit, respectively to, the pseudo-second-order kinetic, and Langmuir isotherm. These both models were found to better describe the metal binding onto the DQ@Fe3O4 surface. This suggested a homogenous monolayer sorption dominated by surface complexation. Additionally, thermodynamic data have shown that the adsorption of heavy metal ions is considered a spontaneous and exothermic process. Moreover, Monte Carlo (MC) simulations were performed in order to elucidate the interactions occurring between the heavy metal ions and the DQ@Fe3O4 nanocomposite surface. A good correlation was found between the simulated and the experimental data. Moreover, based on the negative values of the adsorption energy (Eads), the adsorption process was confirmed to be spontaneous. In summary, the as-prepared DQ@Fe3O4 can be considered a low-cost-effective heavy metals adsorbent, and it has a great potential application for wastewater treatment.

Multifunctional cobalt oxide nanocomposites for efficient removal of heavy metals from aqueous solutions.

In this study, co-precipitation synthesis of natural clay (NC) with Co3O4 nanoparticles (NPs) is carried out to elaborate the super NC@Co3O4 nanocomposites with admirable salinity confrontation, environmental stability and reusability, to eliminate heavy metal pollution such as toxic Pb(II) and Cd(II) ions. The advantages of using the NC@Co3O4 adsorbent are easy synthesis and biocompatibility. In addition, NC@Co3O4 can keep an excellent adsorption capacity by taking into account various environmental parameters such as the pH solution, NC@Co3O4 dose, adsorption process time and the initial heavy metals concentration. Furthermore, FTIR, XRD, TGA, SEM-EDS, TEM and AFM analyses were performed to confirm NC@Co3O4 nanocomposites synthesis and characterisation. The adsorption efficiencies of Pb(II) and Cd(II) ions by NC@Co3O4 nanocomposites were demonstrated to be up to 86.89% and 82.06% respectively. Regarding the adsorption from water onto the NC@Co3O4 nanocomposites, kinetics data were well fitted with PSO kinetic model, whereas a good agreement was found between the equilibrium adsorption and theoretical Langmuir isotherm model leading to maximum adsorption capacities of 55.24 and 52.91 mg/g, for Pb(II) and Cd(II) respectively. Monte Carlo (MC) simulations confirmed the spontaneous of this adsorption based on the negative values of Eads. The MC simulations were performed to highlight the interactions occurring between heavy metal ions and the surface of NC@Co3O4 nanocomposites, these were well correlated with the experimental results. Overall the study showed that NC@Co3O4 nanoadsorbents have strongly versatile applications and are well designed for pollutant removal from wastewater due to their unique adsorptive properties.

Green synthesis of Ag2O nanoparticles using Punica granatum leaf extract for sulfamethoxazole antibiotic adsorption: characterization, experimental study, modeling, and DFT calculation.

Silver oxide (Ag2O) nanoparticles (NPs) were generated by synthesizing green leaf extract of Punica granatum, and afterwards they were used as adsorbent to remove the antibiotic additive sulfamethoxazole (SMX) from aqueous solutions. Prior of their use as adsorbent, the Ag2O NPs were characterized by various methods such as X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), scanning electron microscopy/energy-dispersive X-ray (SEM-EDX), and transmission electron microscopy (TEM). The Ag2O NPs were found to be spherically shaped and stabilized by the constituents of the extract. Further, at SMX antibiotic concentration of 100 mg L-1, the Ag2O NPs achieved almost complete removal of 98.93% within 90 min, and by using 0.8 g L-1 of adsorbent dose at pH=4 and temperature T=308 K. In addition, the experimental data were well fitted with the theoretical Langmuir model indicating homogeneous adsorbed layer of the SMX antibiotic on the Ag2O NPs surface. The maximum uptake capacity was 277.85 mg g-1. A good agreement was also found between the kinetic adsorption data and the theoretical pseudo-second-order model. Regarding the thermodynamic adsorption aspects, the data revealed an endothermic nature and confirmed the feasibility and the spontaneity of the adsorption reaction. Furthermore, the regeneration study has shown that the Ag2O NPs could be efficiently reused for up to five cycles. The geometric structures have been optimized and quantum chemical parameters were calculated for the SMX unprotonated (SMX+/-) and protonated (SMX+) using density functional theory (DFT) calculation. The DFT results indicated that the unprotonated SMX+/- reacts more favorably on the Ag2O surface, as compared to the protonated SMX+. The SMX binding mechanism was predominantly controlled by the electrostatic attraction, hydrogen bond, hydrophobic, and π-π interactions. The overall data suggest that the Ag2O NPs have promising potential for antibiotic removal from wastewater.

Biosynthesis of SiO2 nanoparticles using extract of Nerium oleander leaves for the removal of tetracycline antibiotic.

Tetracycline (TC) is one of the antibiotics that is found in wastewaters. TC is toxic, carcinogenic, and teratogenic. In this study, the tetracycline was removed from water by adsorption using dioxide silicon nanoparticles (SiO2 NPs) biosynthesized from the extract of Nerium oleander leaves. These nanoparticles were characterized using SEM-EDX, BET-BJH, FTIR-ATR, TEM, and XRD. The influences of various factors such as pH solution, SiO2 NPs dose, adsorption process time, initial TC concentration, and ionic strength on adsorption behaviour of TC onto SiO2 NPs were investigated. TC adsorption on SiO2 NPs could be well described in the pseudo-second-order kinetic model and followed the Langmuir isotherm model with a maximum adsorption capacity was 552.48 mg/g. At optimal conditions, the experimental adsorption results indicated that the SiO2 NPs adsorbed 98.62% of TC. The removal of TC using SiO2 NPs was 99.56% at conditions (SiO2 NPs dose = 0.25 g/L, C0 = 25 mg/L, and t = 40 min) based on Box-Behnken design (BBD) combined with response surface methodology (RSM) modelling. Electrostatic interaction governs the adsorption mechanism is attributed. The reusability of SiO2 NPs was tested, and the performance adsorption was 85.36% after the five cycles. The synthesized SiO2 NPs as promising adsorbent has a potential application for antibiotics removal from wastewaters.

Engineering of amine-based binding chemistry on functionalized graphene oxide/alginate hybrids for simultaneous and efficient removal of trace heavy metals: Towards drinking water.

Engineering of versatile binding chemistry on graphene oxide surface using nucleophilic substitution/amidation reactions for highly efficient adsorption of Cd (II), Cu (II) and Pb (II) is herein proposed. Graphene oxide (GO) was used as a precursor for covalent bonding of hexamethylenediamine (HMDA) molecules via the nucleophilic substitution/amidation reactions on epoxy (COC) and carboxyl (COOH) groups to yield hexamethylenediamine functionalized graphene oxide (GO-HMDA) with multiple binding chemistries such as oxygen and nitrogen. Afterwards, GO-HMDA was encapsulated in alginate hydrogel beads with different loadings 5, 10, 15 and 20 wt% to produce Alg/GO-HMDA hybrid adsorbents for the removal of trace heavy metal ions from aqueous solution. Batch adsorption studies showed remarkable adsorption rates reaching 100% for Pb (II), 98.18% for Cu (II) and 95.19 for Cd (II) (~1 mg L-1) with only 15 wt% of GO-HMDA incorporated into the alginate beads. Moreover, Alg/GO-HMDA showed high removal efficiencies of heavy metals from tap water with a removal order of (Pb > Cu > Cd) similar to that observed in single aqueous solution. In Addition, the Alg/GO-HMDA adsorbents displayed excellent regeneration ability for six consecutive adsorption-desorption cycles confirming the high performance and potential of these adsorbents, for real heavy metals remediation in environment and in drinking waters in both single and multiple systems. Finally, the adsorption mechanism of traces heavy metals resulted from several phenomena including the electrostatic interactions occurring between the COOH groups of Alginate and the GO-HMDA surface groups as well as, through chelation interactions occurring between the metal cations and amino-functionalized groups of Alg/GO-HMDA 15 hybrid adsorbent.

Microwave assisted green synthesis of Fe2O3/biochar for ultrasonic removal of nonsteroidal anti-inflammatory pharmaceuticals.

Iron oxide/biochar (Fe2O3/biochar) was prepared by green synthesis via a microwave to evaluate ultrasound-assisted adsorption capacity of Nonsteroidal Anti-inflammatory Drugs (NSAIDs) (salicylic acid, naproxen, and ketoprofen) from the water. Several techniques of characterization, including, Fourier transform infrared spectrometry, scanning electron microscopy, EDS analysis, N2 adsorption-desorption, X-ray diffraction, and Raman spectrometry were applied. The adsorption of NSAIDs onto Fe2O3/biochar was performed using an ultrasonic bath. The effects of batch adsorption under various experimental parameters such as contact time (0-120 min), initial concentration (10-500 mg L-1) and pH (2-12) were tested. The obtained Fe2O3/biochar specific surface area, mesopore volume/micropore volume, and pores size were equal to 786 m2 g-1, 0.409 cm3 g-1, and 1.534 cm3 g-1, respectively. The pseudo-second-order model could describe better all NSAID adsorptions onto Fe2O3/biochar. The Langmuir model agreed well with the NSAID adsorptions and the maximum adsorption capacities reached 683 mg g-1, 533 mg g-1 and 444 mg g-1 for salicylic acid, naproxen, and ketoprofen, respectively. Fe2O3/biochar can be used as an excellent adsorbent for the treatment of NSAIDs in water.

Correction: Microwave assisted green synthesis of Fe2O3/biochar for ultrasonic removal of nonsteroidal anti-inflammatory pharmaceuticals.

[This corrects the article DOI: 10.1039/D0RA00617C.].

New amino group functionalized porous carbon for strong chelation ability towards toxic heavy metals.

Herein, ethylenediamine functionalized porous carbon (PC-ED/1.5) was synthesized, then characterized by various methods and finally used as a functional material for Cu(ii) and Pb(ii) ion removal from water. XPS revealed the presence of numerous functionalities within the surface of PC including -NH and C-N-C groups. Furthermore, S BET, RS, XRD and FTIR analyses confirmed the changes implemented on the PC surface. Thereafter, a systematic study was implemented to analyze the interactions of the PC-ED/1.5 surface with Cu(ii) and Pb(ii) heavy metal ions. Hence, adsorption experiments showed that the PC-ED/1.5 exhibits maximum adsorption capacities of 123.45 mg g-1 and 140.84 mg g-1 for Cu(ii) and Pb(ii), respectively. Moreover, in situ electrostatic interactions occurring between the divalent cation and the PC-ED/1.5 functional groups was investigated. The mechanism involves chelation processes, electrostatic interactions and mechanical trapping of the metal ions in the adsorbent pores. Interestingly, a synergistic effect of the pores and surface active sites was observed. Finally, by using alginate bio-polymer we prepared membrane films of PC-ED/1.5 which showed long-term stability, regeneration capabilities and high mass recovery.

High extent mass recovery of alginate hydrogel beads network based on immobilized bio-sourced porous carbon@Fe3O4-NPs for organic pollutants uptake.

This work goes inside the understanding of organic pollutants adsorption mechanism over network alginate hydrogel beads based on immobilized bio-sourced PC@Fe3O4-NPs (PC@Fe3O4-NPs@Alginate) and highlights its high extent mass recovery in aqueous media. The samples were successfully synthesized, we previously developed porous carbon (PC), which, was used to elaborate PC@Fe3O4-NPs via simple in situ coprecipitation (PC@ Fe3O4-NPs), which was encapsulated by alginate-Ca2+ via the blend crosslinking method. The structural, textural, chemical and morphological proprieties of as prepared materials were studied by XRD, FTIR, Raman spectroscopy, nitrogen adsorption-desorption, XPS, SEM and TEM. The adsorption kinetic and isotherm data were well fitted to the pseudo-second-order and Langmuir models. Magnetic particles exhibited an excellent ability to adsorb methylene blue (MB) from aqueous solutions with maximum MB adsorption capacity of 180.42 mg g-1 (PC@Fe3O4 NPs powder) and 49.66 mg g-1 (beads based PC@Fe3O4-NPs@Alginate). Response surface methodology was used to optimize the removal efficiency of MB from aqueous solution and optimum parameters were determined. Magnetic beads based PC showed good magnetic propriety, long-term stability, regeneration capabilities and high extent mass recovery.

Combined Methane Energy Recovery and Toxic Dye Removal by Porous Carbon Derived from Anaerobically Modified Digestate.

Valorization of agri-food organic waste in order to reach zero waste using cleaner methods is still a challenge. Therefore, both anaerobic co-digestion (ACD) (biological process) and adsorption (physicochemical process) were used in combination for this objective. ACD allows the activation of biodegradable organic matter by microbial action and produces a digestate (co-product). This coproduct was used as a raw material to produce porous carbon having a high specific surface area after chemical treatment using sulfuric acid and thermal activations at temperature T = 350 °C. The resulted material was used for the preparation of core-shell particles with a core made of porous carbon and a shell consisting mainly of alginate and a calcium ion layer. The final core-shell particles were then used for dye treating wastewater and solving the solid-liquid separation problem in the adsorption process. We show here that in the ACD process, significant bio-methane potential (BMP) was produced. Furthermore, the data indicate that 153 L CH4 kg·SV-1 of BMP was produced under optimum conditions of pH = 8 and inoculum/load ratio = 1.2. The overall results concerning the methylene blue (MB) adsorption from water onto the core-shell particles show the occurrence of a maximum adsorbed amount equal to 26.178 mg g-1, and good agreement was found between the experimental adsorption data with pseudo-second-order and Langmuir theoretical models. The response surface methodology coupled with the central composite design has allowed the identification of optimal conditions for MB removal and has led to the elucidation of adsorption mechanism and the regeneration of the adsorbent without the occurrence of the solid/liquid separation problem.