Materials For Environmental Remediation Research Articles

Enhanced visible-light photocatalytic degradation activity of Ti3C2/PDIsm via π–π interaction and interfacial charge separation: Experimental and theoretical investigations

Herein, Ti3C2 MXene nanosheets and perylene diimide supramolecular (PDIsm) were successfully combined via a facile self-assembly method. The apparent rate constant of photodegradation for tetracycline hydrochloride (TCH) and Rhodamine B (RhB) of 1%-Ti3C2/PDIsm (0.079 min−1 and 0.082 min−1) were 2.5 times and 7.2 times higher than that of pure PDIsm, respectively. The introduction of Ti3C2 MXene nanosheets is beneficial to the stacking degree of PDIsm and the adsorption capacity of PDIsm for organic pollutants. Moreover, the excellent electrical conductivity of Ti3C2 also promotes the charge separation, which contributes to more photoelectrons participated in the photodegradation reaction of pollutants and thereby the enhanced photocatalytic performance. Additionally, the density functional theory (DFT) calculation also provides strong evidence for the enhanced photocatalytic degradation activity of Ti3C2/PDIsm structure. Meanwhile, the mechanism exploration indicates that h+, ∙O2– and 1O2 play leading roles in the photocatalytic process. This work provides a new insight into using 2D MXenes as co-catalysts to enhance the activity of self-assembled organic materials for environmental remediation.

Worldwide Research Analysis on Natural Zeolites as Environmental Remediation Materials

Society faces a significant problem in regards to the spread of harmful products in the environment, primarily caused by accelerated growth and resource consumption. Consequently, there is a need for materials to be processed in less harmful ways and to remedy the contaminated sources they generate. Microporous materials have been studied for a long time and are used in waste treatment alternatives. Natural zeolites, on which this study is based, are attractive to the scientific and technological communities, due to their numerous applications as decontaminants and adsorption properties. This study analyzes the intellectual structures of publications related to natural zeolites in environmental remediation, using bibliometric methods to determine their volumes and trends. The methodology comprises of an analysis based on 1582 articles, using VOSviewer software, with data from 1974 to 2020, via the Scopus database. Results reflect a notable increase in publications from the end of the 1990s; the greatest contribution in the area comes from Eurasian countries. The study considers that development in this line of research will continue to increase and serve as a great contribution to preserve the environment in coming years, with themes that focus on water treatment (e.g., drinking water, wastewater, greywater), removal of heavy metals, ammonium, ammonia, and construction.

Effect of carbonaceous fillers on adsorption behavior of multifunctional diatomite-based foams for wastewater treatment

Nowadays the study of the potential applications of multifunctional materials for environmental remediation is one of the main goals of the materials engineering. Multifunctional porous materials, MPMs, incorporate, all in once, different and multiple functionalities that make them suitable for several uses and can satisfy many purposes at the same time. Multifunctional diatomite-based foams with a hierarchical porosity, already produced and characterized to be applied in building as well as aerospace sectors, are proposed as adsorbents for inorganic and organic pollutants removal from wastewaters. Then, the effect of the addition of different carbonaceous nanofillers (graphite, graphene and graphene oxide) on the water purification efficiency of the adsorbent was evaluated. Firstly, pristine MPM showed the best performance in adsorbing Indigo Carmine due to its intrinsic chemism and hierarchical porosity (at macro-, micro- and nano-level), but it is not the best with respect to the Cd2+ adsorption, if compared with the nanocomposites. Among the nanocomposite products, both graphene- and graphene oxide-MPM samples showed a significantly improved adsorption capacity towards Cd2+. This behavior is due to the synergistic effect of the finer morphology, higher available foam surface, and the highly exfoliated fillers, graphene and graphene oxide, which permit a better dispersion into the matrix.

Persulfate-based controlled release beads for in situ chemical oxidation of common organic pollutants

Groundwater contamination by organic pollutants is a growing threat to the environment and human health. As a cost-effective method, in situ chemical oxidation (ISCO) treatment has become a popular technical method to degrade groundwater pollutants. However, conventional ISCO treatment can suffer from a number of operational issues, such as tailing and concentration rebound, and thus the long-term treatment effectiveness is less desirable. As an alternative approach to the conventional ISCO method, controlled release materials are designated to gradually release oxidant chemicals to treat polluted groundwater with an extended chemical release duration and a reduced peak release rate. In this study, novel persulfate-paraffin based controlled release bead (CRB) materials were prepared and tested in a laboratory setting for their applicability in groundwater organic pollution remediation. It shows that bead size and temperature can substantially affect the release kinetics of persulfate from the CRBs, while the impact of solution pH and the presence of matrix anions are insignificant. Moreover, degradation experiments of benzene, toluene, ethylbenzene, and xylene pollutants show that the performance of CRBs, particularly within a short period after being delivered in situ, is on par with the conventional ISCO method using aqueous persulfate. This study expands our understanding and capacity in adopting controlled release materials for groundwater remediation. This study promotes the potential field application of such novel controlled release materials for environmental remediation of groundwater.

Efficient peroxymonosulfate activation in electron-rich/poor reaction sites induced by copper–iron oxide heterojunctions/interfaces: Performance and mechanism

The development of the efficient material for peroxymonosulfate (PMS) activation is of great importance for water treatment. Herein, a novel magnetic Cu/γ-Fe2O3 catalyst with a dual reaction center (DRC) and abundant heterojunctions/interfaces was constructed, in which uniform composite Cu/γ-Fe2O3 nanoparticles were anchored on a thin continuous carbon framework. The asymmetric configuration of the Cu/γ-Fe2O3 catalyst significantly promotes the adsorption and activation of PMS by strengthening Fe–OH coordination and reducing the adsorption energy barrier of interfacial Cu sites. The efficient conversion of SO4•- and the generation of singlet oxygen (1O2) were realized in the Cu and γ-Fe2O3 domains, respectively, owing to the electron polarization distribution in Cu/γ-Fe2O3. Through synergetic multi-pathway activation, tetracycline (TC) underwent efficient degradation over a wide pH range (3–11), and the degradation efficiency was not inhibited by common ions. The reaction rate of Cu/γ-Fe2O3 (0.685 min−1) was 5.1 and 9.8 times higher than that of the non-DRC Cu and γ-Fe2O3 catalysts, respectively. Furthermore, the Cu/γ-Fe2O3 + PMS system exhibited excellent stability and significantly low metal leaching. This work provides a possible approach to address the application bottlenecks of metal-based catalysts as well as to develop novel environmental remediation materials.

Modelling and optimisation by response surface technique for adsorption of carbon dioxide by aminated biosilica/alginate composite: Experiments, characterisation and regeneration studies

ABSTRACT Recently, there has been interest in designing recyclable and economical material for actual environmental remediation. In the present research work, amine-functionalised biosilica/alginate (NH2-SiO2/ALG) composite was evaluated for efficient capture of carbon dioxide (CO2). The morphological and textural properties of NH2-SiO2/ALG composite were comprehensively characterised by BET, SEM, XRD, TGA, and FTIR techniques. The impact of influential factors on the adsorption efficiency procedure was explored in a fixed-bed reactor and the corresponding breakthrough curves were plotted. The optimum value for CO2 removal efficiency (RE)% was predicted as 93.08% at 40°C temperature, 40 mL/min gas flow rate, and 5% moisture content. Under these conditions, the actual CO2 RE% was achieved 92.4%. The exothermic isosteric heat of adsorption (IHA) was found as 25.3–34.8 kJ/mol representing physical interactions between NH2-SiO2/ALG and CO2 molecules. Regeneration tests showed that the synthesised NH2-SiO2/ALG can be effectively recovered and used in multiple runs.

Magnetic hydrochar nanocomposite obtained from sunflower husk: A potential material for environmental remediation

A novel magnetic hydrochar composed of nanosized magnetite (Fe3O4) particles supported on a hydrochar matrix was synthesized via hydrothermal carbonization of sunflower husk, employing phosphoric acid as the activating agent. An exhaustive characterization of the hydrochars and the magnetic hydrochar was undertaken to identify, mainly, the mechanism by which the iron oxide nanoparticles interact with the hydrochar matrix. The magnetic hydrochar exhibited superparamagnetic properties with a saturation magnetization of 55,21 emu/g. BET surface area and pore diameter of the magnetic hydrochar were found to be 55.25 m2/g and 10,49 nm respectively which are in accordance with mesoporous materials. Fourier transform infrared spectroscopy and z potential characterization suggest that the main mechanisms of interaction between the magnetite nanoparticles and the hydrochar matrix were coulombic ones, where carboxyl and hydroxyl oxygen-containing functional groups of the hydrochar were more likely to interact with the iron oxide nanoparticles.

In-situ construction of WC/Bi2WO6 nanocomposites for efficient photodegradation of bisphenol A with peroxymonosulfate activation

Exploring highly efficient catalyst is the key for integration of photocatalysis and peroxymonosulfate (PMS) activation. Herein, WC/Bi2WO6 nanocomposites were judiciously constructed by anchoring the non-noble metal plasmonic WC nanocrystals onto the surface of ultrathin Bi2WO6 nanosheets to activate PMS for efficient photodegradation of bisphenol A (BPA). The prepared WC/Bi2WO6 nanocomposites possess abundant heterojunction interface, resulting in excellent photoabsorption capability, interfacial charge transfer dynamics, and charge carrier concentration. As expected, WC/Bi2WO6 nanocomposites exhibit superior catalytic activity and stability in PMS activation toward BPA degradation with removal efficiency of 97.4%, which is higher than that of Bi2WO6. The content of WC nanocrystals are critical to tune the catalytic activity of the nanocomposites. The intermediates and degradation pathways were determined through LC-MS/MS analysis. Finally, the reaction mechanism was systematically elucidated based on the active species detection, charge transfer dynamics, and band structures. The desirable photocatalytic performances can be ascribed to the constructional heterojunction between the WC nanocrystals and Bi2WO6 nanosheets, which can efficiently enhance the photoabsorption capability, heighten the interfacial charge transfer ability, and ameliorate the charge carrier concentration. This study provides some insights to construct highly efficient photocatalyst modification with non-noble metal based plasmonic materials for environmental remediation.

Facet Engineering of Bismuth Molybdate via Confined Growth in a Nanoscale Template toward Water Remediation.

Certain nanomaterials can filter and alter unwanted compounds due to a high surface area, surface reactivity, and microporous structure. Herein, γ-Bi2MoO6 particles are synthesized via a colloidal hydrothermal approach using organically modified Laponite as a template. This organically modified Laponite interlayer serves as a template promoting the growth of the bismuth molybdate crystals in the [010] direction to result in hybrid Laponite-Bi2MoO6 particles terminating predominantly in the {100} crystal facets. This resulted in an increase in particle size from lateral dimensions of <100 nm to micron scale and superior adsorption capacity compared to bismuth molybdate nanoparticles. These {100}-facet terminated particles can load both cationic and anionic dyes on their surfaces near-spontaneously and retain the photocatalytic properties of Bi2MoO6. Furthermore, dye-laden hybrid particles quickly sediment, rendering the task of particle recovery trivial. The adsorption of dyes is completed within minutes, and near-complete photocatalytic degradation of the adsorbed dye in visible light allowed recycling of these particles for multiple cycles of water decontamination. Their adsorption capacity, facile synthesis, good recycling performance, and increased product yield compared to pure bismuth molybdate make them promising materials for environmental remediation. Furthermore, this synthetic approach could be exploited for facet engineering in other Aurivillius-type perovskites and potentially other materials.

Mechanism of over-stoichiometric oxidation of SO2 by iron oxides modified pyridinic N-doped carbonaceous materials

Transitional metal oxides modified carbonaceous materials was effective for the removal of SO2 from flue gases. However, the local structure of the active sites and the oxidation mechanism remain to be opaque. In this work, iron oxides modified pyridine N-doped graphene was investigated with DFT calculation method. It was found that a four pyridinic N atoms doped defect with Fe2O4 cluster anchored is quite active, leading to an over-stoichiometric SO2/Fe molar ratio as high as 2.5 practically. The catalytic effect is due to the strong electronegativity of pyridinic N atoms, which help to accommodate the electrons of Fe atom in FeOS sulfated cluster and reduce the binding interaction between Fe and O atom. The latter facilitates the release of SO3 and the adsorption and activation of molecular O2. Additionally, the distance between Fe atom of the stabilized cluster and O atom of the adsorbed SO3 or SO4 moiety was proposed to be a descriptor of the capacity of iron oxides modified carbonaceous materials for SO2 removal, which may be used to screen and design new materials for environmental remediation from air pollutions.

Synthesis of imidazolium-based cationic organic polymer for highly efficient and selective removal of ReO4−/TcO4−

Rational design of anion-scavenging materials with high selectivity and stability under high acid/base extreme conditions for removing 99TcO4− is still a significant challenge. Herein, we put forward an anion exchange strategy that utilized an imidazolium-based cationic organic polymer (named ImCOP) for efficient capture of perrhenate (ReO4−), a surrogate for TcO4− with nonradioactive. ImCOP was synthesized via the quaternization reaction using tris (4-(1H-imidazol-1-yl) phenyl) amine, a tripodal flexible ligand, and 1,4-bis (bromomethyl) benzene to forming a semi-rigid structure. ImCOP exhibited high chemical stability even under 3 M HNO3 and 3 M NaOH, which was superior to those of most materials. Attributed to the charged imidazolium moieties and tertiary amine groups that produced rich adsorption sites, ImCOP can produce electrostatic interactions with ReO4−, thereby leading to a record uptake capability (1162 mg g−1) of ReO4−. Furthermore, ImCOP exhibited high selectivity for removing ReO4− in the presence of large excess of competitive anions, which was attributed to the hydrophobic surface of ImCOP. These excellent features endowed ImCOP successfully separated ReO4− from simulated Hanford waste with a high adsorption removal of 93.4%. The excellent performance suggested ImCOP would be a promising material for TcO4−/ReO4− removal, which provided a feasible pathway for designing a high-efficiency and durable material for nuclear-related environmental remediation.

Recent Developments in Understanding Biochar’s Physical–Chemistry

Biochar is a porous material obtained by biomass thermal degradation in oxygen-starved conditions. It is nowadays applied in many fields. For instance, it is used to synthesize new materials for environmental remediation, catalysis, animal feeding, adsorbent for smells, etc. In the last decades, biochar has been applied also to soils due to its beneficial effects on soil structure, pH, soil organic carbon content, and stability, and, therefore, soil fertility. In addition, this carbonaceous material shows high chemical stability. Once applied to soil it maintains its nature for centuries. Consequently, it can be considered a sink to store atmospheric carbon dioxide in soils, thereby mitigating the effects of global climatic changes. The literature contains plenty of papers dealing with biochar’s environmental effects. However, a discrepancy exists between studies dealing with biochar applications and those dealing with the physical-chemistry behind biochar behavior. On the one hand, the impression is that most of the papers where biochar is tested in soils are based on trial-and-error procedures. Sometimes these give positive results, sometimes not. Consequently, it appears that the scientific world is divided into two factions: either supporters or detractors. On the other hand, studies dealing with biochar’s physical-chemistry do not appear helpful in settling the factions’ problem. This review paper aims at collecting all the information on physical-chemistry of biochar and to use it to explain biochar’s role in different fields of application.

Insights into the mechanism of peroxydisulfate activated by magnetic spinel CuFe2O4/SBC as a heterogeneous catalyst for bisphenol S degradation

• CuFe 2 O 4 /SBC was synthesized via hydrothermal method assisted by PEG-20000. • The CuFe 2 O 4 /SBC/PDS system showed superior stability against metal ions leaching. • CuFe 2 O 4 /SBC could efficiently degrade 84.5% BPS in CuFe 2 O 4 /SBC/PDS system. • The adsorbed BPS on CuFe 2 O 4 /SBC could be further degraded. • The surface-bound radical pathways played a more crucial role. The CuFe 2 O 4 catalyst in advanced oxidation processes had received much attention, while the leaching metal ions and its agglomeration limited its application prospect. The conversion of waste activated sludge (WAS) into sludge-derived biochar (SBC) through pyrolysis could not only be the option of reducing the environmental burden but also converted to be the value-added environmental remediation materials. Hence, the present study prepared as a CuFe 2 O 4 /SBC heterogeneous catalyst to degrade new environmental pollutants (bisphenol S, BPS). To our best knowledge, CuFe 2 O 4 /SBC as a heterogeneous catalyst activating peroxydisulfate to degrade BPS in solution is rarely reported, and the catalytic performances and degradation mechanism of CuFe 2 O 4 /SBC need to be comprehensively investigated. The synergistic effect between CuFe 2 O 4 and SBC enhanced catalytic performances and alleviated agglomeration. The CuFe 2 O 4 /SBC was greatly ameliorated metal ions leaching, but the synthetic strategy could better optimize to further reducing Cu ion leaching. The dominant role of heterogeneous catalysis by CuFe 2 O 4 /SBC also have been elucidated. It was proposed that radical ( OH and SO 4 − ) and non-radical ( 1 O 2 ) oxidation processes worked together for BPS degradation, but surface-bound radical pathways played more crucial roles. Some intermediate products with higher toxicity may be produced due to the non-completely mineralized, thus future attention should be paid to their environmental risks. Hence, the detoxification efficiency of CuFe 2 O 4 /SBC needs to be further strengthened via improving the reaction conditions. Overall, this study provided a new strategy to simultaneously solve the problems of WAS disposal and leaching metal ions of CuFe 2 O 4 .

Multi-component Zn2SnO4/MoS2/Ag/AgCl for enhancing solar-driven photoelectrocatalytic activity

In this study, efficient photoelectrocatalyst Zn2SnO4/MoS2/Ag/AgCl (ZTO/MoS2/Ag/AgCl) was prepared by hydrothermal method followed with the in-situ deposition process. ZTO/MoS2/Ag/AgCl electrode exhibited significant photoelectrocatalytic activity by degrading Methylene Blue (MB) and phenol of 96.5% and 68% respectively under simulated solar light within 2 h. According to a series of analysis and characterization, the results indicated that the multi-component ZTO/MoS2/Ag/AgCl not only broadened the visible light response ranges, but also restrained the recombination of charge carriers remarkably, which was due to the synergistic of SPR effect of Ag particles, and the agglomeration status in the special flake structures of MoS2. In addition, MoS2 also functioned as an electron mediator. Based on our results, we proposed a rational schematic mechanism for improved photoelectrocatalytic performance. This research provided exceptional insights for the use of zinc stannate-based materials for environmental remediation.

Modulation of the Bifunctional CrVI to CrIII Photoreduction and Adsorption Capacity in ZrIV and TiIV Benchmark Metal-Organic Frameworks

The presence of hexavalent chromium water pollution is a growing global concern. Among the currently applied technologies to remove CrVI, its adsorption and photocatalytic reduction to CrIII less mobile and toxic forms are the most appealing because of their simplicity, reusability, and low energy consumption. However, little attention has been paid to bifunctional catalysts, that is, materials that can reduce CrVI to CrIII and retain both hexavalent and trivalent chromium species at the same time. In this work, the dual CrVI adsorption–reduction capacity of two iconic photoactive water-stable zirconium and titanium-based metal–organic frameworks (MOFs) has been investigated: UiO-66-NH2 and MIL-125. The bifunctionality of photoactive MOFs depends on different parameters, such as the particle size in MIL-125 or organic linker functionalization/defective positions in UiO-66 type sorbents. For instance, the presence of organic linker defects in UiO-66 has shown to be detrimental for the chromium photoreduction but beneficial for the retention of the CrIII phototransformed species. Both compounds are able to retain from 90 to 98% of the initial chromium present at acidic solutions as well as immobilize the reduced CrIII species, demonstrating the suitability of the materials for CrVI environmental remediation. In addition, it has been demonstrated that adsorption can be carried out also in a continuous flux mode through a diluted photoactive MOF/sand chromatographic column. The obtained results open the perspective to assess the bifunctional sorption and photoreduction ability of a plethora of MOF materials that have been applied for chromium capture and photoreduction purposes. In parallel, this work opens the perspective to develop specific chemical encoding strategies within MOFs to transfer this bifunctionality to other related water remediation applications.

Graphdiyne: an emerging two-dimensional (2D) carbon material for environmental remediation

This review highlights recent and important advances related to the structure properties and application of graphdiyne (GDY)-based nanocomposites for environmental remediation.

2D and 3D Bulk Materials for Environmental Remediation: Air Filtration and Oil/Water Separation.

Air and water pollution pose an enormous threat to human health and ecosystems. In particular, particulate matter (PM) and oily wastewater can cause serious environmental and health concerns. Thus, controlling PM and oily wastewater has been a great challenge. Various techniques have been reported to effectively remove PM particles and purify oily wastewater. In this article, we provide a review of the recent advancements in air filtration and oil/water separation using two- and three-dimensional (2D and 3D) bulk materials. Our review covers the advantages, characteristics, limitations, and challenges of air filters and oil/water separators using 2D and 3D bulk materials. In each section, we present representative works in detail and describe the concepts, backgrounds, employed materials, fabrication methods, and characteristics of 2D and 3D bulk material-based air filters and oil/water separators. Finally, the challenges, technical problems, and future research directions are briefly discussed for each section.

From scrap polystyrene foam to efficient demercurizer: In-situ synthesis of Fe-embedded hyper-cross-linked polymers

Limiting mercury emission is imperative to clean production of coal-fired power plants. This work proposes a one-pot catalysis approach to in-situ reclaim scrap Styrofoam into Fe-embedded hyper-cross-linked polymers (HCP-Fe) for gaseous Hg° decontamination. Such approach renders demercurizer synthesis more environment-benign and cost-efficient than existing methods. The resulting HCP-Fe samples exhibit conspicuous pore features (BET surface areas: 423.71∼1158.40 m2/g), remarkable demercuration performance at wide-range temperatures (60∼180 °C), and desirable adaptability to both humid and acid flue gas settings, thereby, surpassing their Fe-cleaned counterparts and current state-of-the-art materials. Experimental and theoretical investigations indicate in-situ FeCl3 embedding endows Styrofoam-based HCPs with homodisperse Hg°-affinitive sites in porous framework, thus facilitating the effective Hg° trapping under various flue gas conditions; while inherent interconnected channels inside HCP-Fe further expedite the mass transfer for Hg° catalytic oxidation. Our attempt manifests a potential guideline to recycling waste plastics into value-enhancing materials for environmental remediation.

Developing scenario of titania-based building materials for environmental remediation

The present review article is aimed at analysing the different aspects of titania-modified building materials towards environmental remediation. The possibility of degradation of different toxic environmental pollutants like VOCs and NOx by the titania-modified paints, cements and other building materials has been discussed. The major role of titania resides in its photocatalytic activity that renders the materials’ potent for degrading these obnoxious compounds. The application of TiO2 both in small and in large scale and the mutual relationship of the amount of TiO2 with the amount of main building block constituents are discussed in detail. Application of daylight or lamplight, energy, time, and atmospheric conditions has also been dealt with. This review article solely focuses on titania-incorporated building blocks and is an endeavour to propagate a new horizon for our future pollution-free perspectives. Several environmental and product-related parameters that affect the efficacy of these modified matrices have been taken up. The present scenario in the industrial fields has also been assessed. Finally, a critical view is also presented that highlights the shortfall and areas open for further research and development in this particular field.

Construction of novel trimeric π-interaction subphthalocyanine-sensitized titanium dioxide for highly efficient photocatalytic degradation of organic pollutants

In this study, highly active TiO2 sensitized by a novel axial substituted subphthalocyanine H12SubPcB-OPHCH2COOH (SubPc-3) was successfully prepared via a solvothermal method. Based on the crystallographic strategy, a new packing motif of SubPc-3 consisting of ligand-convex concave-concave head-head π-interaction was discovered for the first time, which affected its catalytic performance significantly. Furthermore, the DFT and TD-DFT methods were used to study the electronic feature and excited-state properties in SubPc-3 utilizing an optimized structure. By examining the degradation of methyl orange (MO) and bromophenol blue (BB) under visible light, the photocatalytic activities of the nanocomposites were investigated. The photocatalytic degradation rate of MO and BB degradation with TiO2/SubPc-3 are 97.8% and 99.5%, which are approximately 5.26 and 1.41 times compared to pure TiO2, respectively. Besides, the reusability studies indicated that the photocatalytic activity of TiO2/SubPc-3 (25:1) could be maintained above 90.1% after five circulating photo-degradation. This work revealed the correlation between π-interaction of sensitizer and photocatalytic performance, as well as further confirmed the great potential of TiO2/SubPc-3 photocatalytic materials in environmental remediation.