Environmental Pollution Cleanup Research Articles

In-situ growth of hierarchical layered double hydroxide on polydopamine-encapsulated hollow Fe3O4 microspheres for efficient removal and recovery of U(VI)

With the increasing demand of nuclear power plant, the depleted uranium is inevitably emitted and causes environmental risk, hence it is crucial to develop new methods to efficiently eliminate uranium compounds from water. In this work, a bifunctional material core-shell-shell layered double hydroxide (LDH) decorated hollow magnetic polydopamine (MP) microspheres (defined as MPL) were synthesized and evaluated for the cleanup of uranium (VI) from aqueous solutions through specific adsorption. The experimental results showed that the adsorption was significantly affected by pH value rather than ionic strength, reflecting that the interaction was mainly governed by inner-sphere surface complexation owing to the multiple functional groups including imine, catechol, amine, and hydroxyl groups. The adsorption kinetics can be perfectly depicted by the pseudo-second-order model with high uptake percentage of 94.8%, which was superior to the previously reported materials. Interestingly, the maximum adsorption performance can be tuned by changing the thickness of polydopamine shell and the content of LDH, in the order of MP2L2 (344 mg/g) > MP2L3 (291 mg/g) > MP3L2 (245 mg/g) > MP2L1 (211 mg/g) > ML2 (142 mg/g) > MP1L2 (141 mg/g) > MP2 (71 mg/g) > Fe3O4 (34 mg/g) at 298.15 K and pH 5.0. The adsorption mechanism has been thoroughly investigated with techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), X-ray diffraction (XRD), thermo-gravimetric analyses (TGA), Fourier transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). In summary, the bifunctional material could be applied as promising building block for the enrichment and recovery of uranium (VI) from aqueous solutions in environmental pollution cleanup.

Removal of radionuclides by metal oxide materials and mechanism research

With the development of civil nuclear industry, “radioactive contamination” has aroused worldwide public attention increasingly. The study on the interaction of radionuclides at solid-liquid interfaces can lead to a more profound comprehension of its diffusion, migration and transformation in the natural environment, which would make the disposal and control of radioactive wastes more effectively. The metal oxide materials have shown great potential applications in the field of radionuclides’ removal, which are mainly attributed to their multiple advantages, such as the sufficiency, the low cost, the environmental friendliness and the large sorption capacity. Herein, we reviewed the application of commonly used metal oxide materials (such as iron oxides, layered double oxides, aluminum oxides and titanium dioxides) in the sorption of radionuclides from large volumes of aqueous solutions in the last five years. The sorption properties and the main interaction mechanism were investigated and discussed through batch experiments, surface complexation models, spectroscopic techniques and theoretical calculations. Moreover, the application of the metal oxide materials in environmental radioactive pollution cleanup was also discussed. Therefore, we hope that this work would be helpful to further investigation and application of metal oxide materials in environmental radionuclide pollution management.

Synthesis and application of sulfonated polystyrene/ferrosoferric oxide/diazoresin nanocomposite microspheres for highly selective removal of dyes

A versatile porous adsorbent of sulfonated polystyrene/ferrosoferric oxide/diazoresin (SPS/Fe3O4/DR) nanocomposite microspheres with magnetic property and acidic/basic groups was prepared and applied for removal of different dyes from water. The adsorbent showed good adsorption performance due to its functional groups and strong adsorption forces. The selective removal of methylene blue (MB) from MB/methyl orange (MO) mixture can be realized using this adsorbent. The adsorption uptake capacity of the adsorbents was 223.71mg/g and the removal efficiency was more than 90% even after five adsorption-desorption cycles. This adsorbent could be readily separated from solution within 2min using a magnet. Furthermore, adsorption kinetics for SPS/Fe3O4/DR followed by the pseudo-second order model. Isothermal equilibrium data were fitted with Langmuir model, which indicated the adsorption process is the monolayer adsorption. This novel, low cost and high effective adsorbent possesses great potential in environmental pollution cleanup.

Enhanced degradation of organic pollutants over Cu-doped LaAlO3 perovskite through heterogeneous Fenton-like reactions

Cu-doped LaAlO3 perovskite (LaAl1−xCuxO3) was synthesized via a Pechini-type sol–gel process for the oxidative degradation of persistent organic compounds. The characterization results show that Cu was incorporated into the structure of sphere-like LaAlO3 and formed the bond of La/AlOCu. LaAl0.95Cu0.05O3 performed excellent activity and stability for the degradation and mineralization of various organic pollutants through heterogeneous Fenton-like reactions. In the practical reaction process, at the organic pollutant initial concentration of 25mgL−1, 1.0mol H2O2 produces 1.8mol HO radicals within 60min and 1.0mol H2O2 still produces 1.3mol HO radicals after reaction time of 240min. The results of ESR and active species trapping experiments indicated that HO radicals acted the dominant role during the degradation of pollutants in LaAl0.95Cu0.05O3/H2O2 system. Combining with in-situ Raman analysis and the XPS results of LaAl0.95Cu0.05O3 before and after reaction, H2O2 was predominantly reduced to HO on the electron-rich Cu center, and H2O2/H2O can be dissociated on oxygen vacancies (OVs) to enhance formation of HO on the surface of LaAl0.95Cu0.05O3, resulting in the high catalytic activity of LaAl0.95Cu0.05O3. This efficient material can potentially be used as a promising catalyst for the efficient degradation of organic pollutants in environmental pollution cleanup.

Exploitation of Ag<sub>3</sub>PO<sub>4</sub> Impregnated Alginate Beads for the Photocatalytic Degradation of Dye Solution under Sunlight Irradiation

Ag3PO4-alginate beads (AAB) were synthesized by simple precipitation method and their structure was characterized by XRD, FT-IR and SEM/EDS, respectively. The AAB was evaluated as the photocatalyst for degradation of methylene blue (MB) under sunlight irradiation. The results showed that AAB exhibited the high performance for degradation of MB (97.6%) in 60 min. The kinetic studied demonstrated that the photocatalytic reactions followed the pseudo first-order model. Moreover, AAB can maintain full photodegradation activity for at least five cycles. Consequently, the AAB are promising materials for the photocatalytic of dyes or similar organic contaminant in environmental pollution cleanup.

Magnetic carbon aerogel pyrolysis from sodium carboxymethyl cellulose/sodium montmorillonite composite aerogel for removal of organic contamination

In this paper, we present a facile approach for the synthesis of polysaccharide-based carbon aerogel by sol–gel processing, freeze-drying, and pyrolysis of a sodium carboxymethyl cellulose/sodium montmorillonite composite aerogel. The as-prepared carbon aerogel was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, nitrogen adsorption measurements, and vibrating sample magnetometry. The carbon aerogel obtained in this study possessed low density (0.064 ± 0.0029 g/cm3), a high surface area (185 m2/g), and flame retardance. Measurements of the magnetic properties indicated that the carbon aerogel exhibited typical ferromagnetic characteristic at room temperature. The absorption capacity of the carbon aerogel for oils and organic solvents is as much as 10–20 times its own weight. Moreover, a method of combustion could be employed to recycle the carbon aerogel. The results imply that the carbon aerogel is a potential cost-effective adsorbent for oil and organic pollutants from aqueous solutions in environmental pollution cleanup.

Synthesis of layered titanate nanowires at low temperature and their application in efficient removal of U(VI)

Uranium(VI) has become one of the most potential contaminants due to its productive and irreversibility impact on the surrounding environment. Titanate nanowires (TNWs) have attracted significant attention because of its high ion exchange ability and facile synthesis. Herein the TNWs were synthesized, and the morphology and structure of TNWs were investigated by Fourier transformed infrared spectroscopy, scanning electron microscope, transmission electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy in detail. The application of TNWs in U(VI) removal was studied under various environmental conditions using batch technique, and the results indicated that the sorption of U(VI) on TNWs was strongly affected by pH and weakly affected by ionic strength. The presence of PO43- and CO32- could overwhelmingly influence U(VI) interaction with TNWs, which was mainly attributed to the formation of anionic and electro-neutral complexes. From the Langmuir model simulation, the maximum sorption capacities were calculated to be 358, 384, and 410 mg g−1 at the temperatures of 298 K, 313 K and 328 K, respectively. The thermodynamic results revealed that the interaction process was spontaneous and endothermic. The extraordinary ion exchange capacity and facile synthesis under mild conditions made TNWs promising materials for the potential application in the efficient elimination of U(VI) or other lanthanides and actinides from aqueous solutions in the environmental radioactive pollution cleanup.

Rational design and synthesis of monodispersed hierarchical SiO2@layered double hydroxide nanocomposites for efficient removal of pollutants from aqueous solution

Hierarchical silicon dioxide-@-layered double hydroxide (SiO2@LDH) nanocomposites were synthesized by a facile in situ co-precipitation method, and characterized by XRD, FESEM, FT-IR and XPS in detail. The sorption of uranium (U(VI)) and methyl orange (MO) on SiO2@LDH were investigated as a function of pH, ionic strength, contact time and temperature. The results indicated that the sorption of U(VI) and MO were strongly dependent on pH, and weakly dependent on ionic strength, demonstrating that the interaction of U(VI) was mainly dominated by inner-sphere surface complexation and the sorption of MO was mainly attributed to electrostatic attraction due to the high removal efficiency (∼98% within 4h for U(VI) ions, and ∼92% within 10min for MO). The kinetics sorption of U(VI) and MO both followed the pseudo-second-order model well, suggesting that the sorption processes were chemical sorption. The sorption isotherms of U(VI) and MO on SiO2@LDH were well fitted by the Langmuir model, and the maximum sorption capacities of SiO2@LDH were calculated to be 303.1mg·g−1 for U(VI) and 166.1mg·g−1 for MO. The thermodynamic parameters revealed that the sorption of U(VI) and MO was spontaneous process. Integrating the experimental result analysis, the hierarchical SiO2@LDH may be a promising material for the efficient elimination of radionuclides and dyes from aqueous solutions in natural environmental pollution cleanup.

The role of graphene oxide and graphene oxide-based nanomaterials in the removal of pharmaceuticals from aqueous media: a review.

In this review paper, the ill effects of pharmaceuticals (PhAs) on the environment and their adsorption on graphene oxide (GO) and graphene oxide-based (GO-based) nanomaterials have been summarised and discussed. The adsorption of prominent PhAs discussed herein includes beta-blockers (atenolol and propranolol), antibiotics (tetracycline, ciprofloxacin and sulfamethoxazole), pharmaceutically active compounds (carbamazepine) and analgesics such as diclofenac. The adsorption of PhAs strictly depends upon the experimental conditions such as pH, adsorbent and adsorbate concentrations, temperature, ionic strength, etc. To understand the adsorption mechanism and feasibility of the adsorption process, the adsorption isotherms, thermodynamics and kinetic studies were also considered. Except for some cases, GO and its derivatives show excellent adsorption capacities for PhAs, which is crucial for their applications in the environmental pollution cleanup.

Effect of Mixing Ratio and Doping Acid on the Photocatalytic Properties of PANI-BiVO4 Composites

BiVO4 photocatalyst prepared by hydrothermal method was mixed with polyaniline (PANI). The phase structure, morphology and optical properties of PANI-BiVO4 photocatalysts were analyzed through X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Vis diffuse reflectance spectroscopy (DRS). The results showed that the optimal preparation conditions of composite photocatalyst were 0.5wt.% PANI mixing ratio and H3PO4 as doping acid. The photocatalysis degradation rate is the highest. This new heterogeneous structure photocatalyst is expected to show considerably potential applications in solar-driven environmental pollution cleanup.

Superior coagulation of graphene oxides on nanoscale layered double hydroxides and layered double oxides

With the development and application of graphene oxides (GO), the potential toxicity and environmental behavior of GO has become one of the most forefront environmental problems. Herein, a novel nanoscale layered double hydroxides (glycerinum-modified nanocrystallined Mg/Al layered double hydroxides, LDH-Gl), layered double oxides (calcined LDH-Gl, LDO-Gl) and metallic oxide (TiO2) were synthesized and applied as superior coagulants for the efficient removal of GO from aqueous solutions. Coagulation of GO as a function of coagulant contents, pH, ionic strength, GO contents, temperature and co-existing ions were studied and compared, and the results showed that the maximum coagulation capacities of GO were LDO-Gl (448.3 mg g−1) > TiO2 (365.7 mg g−1) > LDH-Gl (339.1 mg g−1) at pH 5.5, which were significantly higher than those of bentonite, Al2O3, CaCl2 or other natural materials due to their stronger reaction active and interfacial effect. The presence of SO32− and HCO3− inhibited the coagulation of GO on LDH-Gl and LDO-Gl significantly, while other cations (K+, Mg2+, Ca2+, Ni2+, Al3+) or anion (Cl−) had slightly effect on GO coagulation. The interaction mechanism of GO coagulation on LDO-Gl and TiO2 might due to the electrostatic interactions and strong surface complexation, while the main driving force of GO coagulation on LDH-Gl might be attributed to electrostatic interaction and hydrogen bond, which were further evidenced by TEM, SEM, FT-IR and XRD analysis. The results of natural environmental simulation showed that LDO-Gl, TiO2 or other kinds of natural metallic oxides could be superior coagulants for the efficient elimination of GO or other toxic nanomaterials from aqueous solutions in real environmental pollution cleanup.

Layered double hydroxide intercalated with aromatic acid anions for the efficient capture of aniline from aqueous solution

Aniline is toxic and hard to be degraded, and thereby causes the environmental pollution seriously. Herein, a practical and green hydrothermal method was applied to fabricate terephthalic acid and pyromellitic acid intercalated layered double hydroxides (LDH) (named as TAL and PAL) for aniline efficient removal. The sorption of aniline on LDH-based materials were investigated at different experimental conditions, and the results indicated that aniline sorption on LDH, TAL and PAL were strongly dependent on pH and independent of ionic strength. The maximum sorption capacities of aniline on TAL and PAL at pH 5.0 and 293K were 90.4 and 130.0mg/g, respectively, which were significantly higher than that of aniline on LDH (52.6mg/g). Based on the BET, FTIR and XPS analysis, the higher sorption capacities of TAL and PAL were mainly due to high surface area and basal spacing as well as the abundant functional groups (e.g. –COO−). The interactions of aniline with TAL and PAL were mainly dominated by hydrogen bonds and electrostatic interactions. Such a facile synthesis method, efficient removal performance and superior reusability indicated that the aromatic acid modified LDH materials had potential application for efficient treatment of organic pollutants in environmental pollution cleanup.

Recent advances in synthetic biosafety.

Synthetically engineered organisms hold promise for a broad range of medical, environmental, and industrial applications. Organisms can potentially be designed, for example, for the inexpensive and environmentally benign synthesis of pharmaceuticals and industrial chemicals, for the cleanup of environmental pollutants, and potentially even for biomedical applications such as the targeting of specific diseases or tissues. However, the use of synthetically engineered organisms comes with several reasonable safety concerns, one of which is that the organisms or their genes could escape their intended habitats and cause environmental disruption. Here we review key recent developments in this emerging field of synthetic biocontainment and discuss further developments that might be necessary for the widespread use of synthetic organisms. Specifically, we discuss the history and modern development of three strategies for the containment of synthetic microbes: addiction to an exogenously supplied ligand; self-killing outside of a designated environment; and self-destroying encoded DNA circuitry outside of a designated environment.

Enhanced removal of methyl orange on calcined glycerol-modified nanocrystallined Mg/Al layered double hydroxides

The uncalcined glycerol-modified nanocrystallined Mg/Al layered double hydroxides (named as G-LDH) and calcined G-LDH (named as G-LDO) with molar ratio of Mg:Al=3:1 were successfully synthesized using an easy and green hydrothermal method, and were characterized by scanning electron microscopy, transmission electron microscopy, N2 Brunauer–Emmett–Teller surface area measurement, Fourier transformed infrared (FT-IR) spectroscopy and X-ray diffraction (XRD). The as-synthesized G-LDH and G-LDO were applied as adsorbents to remove methyl orange (MO) from aqueous solutions at different experimental conditions, and the results showed that the interaction of MO with G-LDH and G-LDO were strongly pH-dependent and ionic strength-independent. Kinetic study indicated the MO adsorption on G-LDH and G-LDO were well simulated by pseudo-second-order model. The MO adsorption on G-LDH and G-LDO were well simulated by Langmuir model, and the maximum adsorption capacity of G-LDO (qmax=1062.3mg/g) was much higher than that of G-LDH (qmax=443.5mg/g) at pH=4.5. The thermodynamic parameters calculated from temperature-dependent isotherms indicated that the adsorption was spontaneous and exothermal process. The FT-IR and XRD analysis further evidenced that the interaction of MO with G-LDH was mainly dominated by electrostatic interaction, ion exchange, hydrogen bonding and surface complexation, whereas the uptake of MO to G-LDO was mainly attributed to electrostatic interaction and surface complexation. These results suggested that the G-LDO was a promising material for the efficient removal of organic pollutants in real environmental pollution cleanup.

Application of cryptocrystalline magnesite-bentonite clay hybrid for defluoridation of underground water resources: implication for point of use treatment

A new synthesis method was established to fabricate a nanocomposite material comprising of cryptocrystalline magnesite and bentonite clay that has high adsorption capacity for ionic pollutants. To synthesize the composite at 1:1 weight (g): weight (g) ratio, a vibratory ball mill was used. Batch adsorption experiments were carried out to determine optimum conditions for fluoride adsorption. Parameters optimized included: time, dosage, concentration and pH. Optimum conditions for defluoridation were found to be 30 min of agitation, 0.5 g of dosage, 0.5:100 solid to liquid (S/L) ratios and 25 mg L−1 of initial fluoride ions. Fluoride removal was independent of pH. The adsorption kinetics and isotherms were well fitted by pseudo-second-order and Langmuir models, respectively, indicating chemical and monolayer adsorption. Findings illustrated that the newly synthesized adsorbent was a promising adsorbent for the environmental pollution clean-up of excess fluoride in underground water and it can be used as a point source treatment technology in rural areas of South Africa and other developing countries.

Environmental Remediation and Application of Nanoscale Zero-Valent Iron and Its Composites for the Removal of Heavy Metal Ions: A Review.

The presence of heavy metals in the industrial effluents has recently been a challenging issue for human health. Efficient removal of heavy metal ions from environment is one of the most important issues from biological and environmental point of view, and many studies have been devoted to investigate the environmental behavior of nanoscale zerovalent iron (NZVI) for the removal of toxic heavy metal ions, present both in the surface and underground wastewater. The aim of this review is to show the excellent removal capacity and environmental remediation of NZVI-based materials for various heavy metal ions. A new look on NZVI-based materials (e.g., modified or matrix-supported NZVI materials) and possible interaction mechanism (e.g., adsorption, reduction and oxidation) and the latest environmental application. The effects of various environmental conditions (e.g., pH, temperature, coexisting oxy-anions and cations) and potential problems for the removal of heavy metal ions on NZVI-based materials with the DFT theoretical calculations and EXAFS technology are discussed. Research shows that NZVI-based materials have satisfactory removal capacities for heavy metal ions and play an important role in the environmental pollution cleanup. Possible improvement of NZVI-based materials and potential areas for future applications in environment remediation are also proposed.

Facile preparation of amino functionalized graphene oxide decorated with Fe3O4 nanoparticles for the adsorption of Cr(VI)

A novel ternary magnetic composite consisting of graphene oxide (GO), diethylenetriamine and Fe3O4 nanoparticles (AMGO) were synthesized by a facile one-step reaction route and characterized. The AMGO was applied as a magnetic adsorbent for the Cr(VI) removal from aqueous solutions and the magnetic separation process only took 40s. The maximum adsorption capacity of the AMGO for Cr(VI) was 123.4mg/g, displaying a high efficiency for the removal of Cr(VI), which was much higher than that of MGO. The removal process was pH dependence, endothermic and spontaneous. The pseudo-second-order model described well the adsorption kinetic data and the Langmuir isotherm model fitted the experimental data better than the Freundlich isotherm model. XPS analysis revealed that the Cr(VI) was reduced to the low-toxicity Cr(III) during the adsorption process. Both the Cr(VI) adsorption and subsequent reduction of adsorbed Cr(VI) to Cr(III) contributed to the Cr(VI) removal. In addition, the excellent reproducibility indicate that the AMGO may be a promising adsorption material for the separation and preconcentration of Cr(VI) ions from aqueous solutions in environmental pollution cleanup.

Impact of key geochemical parameters on the attenuation of Pb(II) from water using a novel magnetic nanocomposite: fulvic acid-coated magnetite nanoparticles

In recent years, magnetic nanoparticles have been widely utilized as promising adsorbents for fast and effective attenuation of metal ions in water in environmental pollution control. Herein, a novel magnetic nanocomposite, namely fulvic acid (FA)-coated Fe3O4 nanoparticles (Fe3O4/FA), was utilized for the attenuation of Pb(II) in water by an adsorption process. The results indicated that the coated FA reduced the surface oxidation and agglomeration of Fe3O4 particles and thus promoted the performance of Fe3O4/FA towards Pb(II) removal. The results indicate that Pb(II) adsorption on Fe3O4/FA obtained equilibrium in less than 2 h. Besides, the adsorption of Pb(II) on Fe3O4/FA is strongly dependent on medium pH, and independent of ionic strength and the type of coexisted ions. So, inner-sphere surface complexation mainly controls Pb(II) uptake on Fe3O4/FA. The Fe3O4/FA also showed good regeneration property and separation convenience for the treatment of Pb(II). Besides, XPS is used to study the mechanism at a molecular level and to identify the species of Pb(II) on Fe3O4/FA. Results of this study showed that the magnetic Fe3O4/FA is a promising sequestrator for the attenuation and separation of heavy metal ions in water in environmental pollution cleanup.

Understanding the adsorption mechanism of Ni(II) on graphene oxides by batch experiments and density functional theory studies

The graphene oxides (GOs) have attracted multidisciplinary study because of their special physicochemical properties. The high surface area and large amounts of oxygen-containing functional groups make GOs suitable materials for the efficient elimination of heavy metal ions from aqueous solutions. Herein the sorption of Ni(Ⅱ) on GOs was studied using batch experiments, and the results showed that the sorption of Ni(Ⅱ) is strongly dependent on pH and ionic strength at pH 8. The sorption of Ni(Ⅱ) is mainly dominated by outer-sphere surface complexation and ion exchange at low pH, and by inner-sphere surface complexation at high pH. The interaction of Ni(Ⅱ) with GOs was also investigated by theoretical density functional theory (DFT) calculations, and the results show that the sorption of Ni(Ⅱ) on GOs is mainly attributed to the -COH and -COC groups and the DFT calculations show that Ni(Ⅱ) forms stable GO_Ni_triplet structure with the binding energy of -39.44 kcal/mol, which is in good agreement with the batch sorption experimental results. The results are important for the application of GOs as adsorbents in the efficient removal of Ni(Ⅱ) from wastewater in environmental pollution cleanup.

Surface Modification of Graphene Oxides by Plasma Techniques and Their Application for Environmental Pollution Cleanup.

Graphene oxides (GOs) have come under intense multidisciplinary study because of their unique physicochemical properties and possible applications. The large amount of oxygen-containing functional groups on GOs leads to a high sorption capacity for the removal of various kinds of organic and inorganic pollutants from aqueous solutions in environmental pollution cleanup. However, the lack of selectivity results in difficulty in the selective removal of target pollutants from aqueous solutions in the presence of other coexisting pollutants. Herein, the surface grafting of GOs with special oxygen-containing functional groups using low-temperature plasma techniques and the application of the surface-modified GOs for the efficient removal of organic and inorganic pollutants in environmental pollution are reviewed. This paper gives an account of our research on the application of GO-based nanomaterials in environmental pollution cleanup, including: (1) the synthesis and surface grafting of functional groups on GOs, summarizing various types of low-temperature plasma techniques for the synthesis of graphene/GOs; and (2) the application of graphene/GOs and their composites for the efficient removal of organic and inorganic pollutants from aqueous solutions, including the interaction mechanism according to recently published results.