Over the last 60 years plastics production has increased manifold, owing to their inexpensive, multipurpose, durable and lightweight nature. These characteristics have raised the demand for plastic materials that will continue to grow over the coming years. However, with increased plastic materials production, comes increased plastic material wastage creating a number of challenges, as well as opportunities to the waste management industry. The present overview highlights the waste management and pollution challenges, emphasising on the various chemical substances (known as “additives”) contained in all plastic products for enhancing polymer properties and prolonging their life. Despite how useful these additives are in the functionality of polymer products, their potential to contaminate soil, air, water and food is widely documented in literature and described herein. These additives can potentially migrate and undesirably lead to human exposure via e.g. food contact materials, such as packaging. They can, also, be released from plastics during the various recycling and recovery processes and from the products produced from recyclates. Thus, sound recycling has to be performed in such a way as to ensure that emission of substances of high concern and contamination of recycled products is avoided, ensuring environmental and human health protection, at all times.
The contamination of fresh water is a global concern. The huge impact of natural and anthropogenic organic substances that are constantly released into the environment, demands a better knowledge of the chemical status of Earth’s surface water. Water quality monitoring studies have been performed targeting different substances and/or classes of substances, in different regions of the world, using different types of sampling strategies and campaigns. This review article aims to gather the available dispersed information regarding the occurrence of priority substances (PSs) and contaminants of emerging concern (CECs) that must be monitored in Europe in surface water, according to the European Union Directive 2013/39/EU and the Watch List of Decision 2015/495/EU, respectively. Other specific organic pollutants not considered in these EU documents as substances of high concern, but with reported elevated frequency of detection at high concentrations, are also discussed. The search comprised worldwide publications from 2012, considering at least one of the following criteria: 4 sampling campaigns per year, wet and dry seasons, temporal and/or spatial monitoring of surface (river, estuarine, lake and/or coastal waters) and ground waters. The highest concentrations were found for: (i) the PSs atrazine, alachlor, trifluralin, heptachlor, hexachlorocyclohexane, polycyclic aromatic hydrocarbons and di(2-ethylhexyl)phthalate; (ii) the CECs azithromycin, clarithromycin, erythromycin, diclofenac, 17α-ethinylestradiol, imidacloprid and 2-ethylhexyl 4-methoxycinnamate; and (iii) other unregulated organic compounds (caffeine, naproxen, metolachlor, estriol, dimethoate, terbuthylazine, acetaminophen, ibuprofen, trimethoprim, ciprofloxacin, ketoprofen, atenolol, Bisphenol A, metoprolol, carbofuran, malathion, sulfamethoxazole, carbamazepine and ofloxacin). Most frequent substances as well as those found at highest concentrations in different seasons and regions, together with available risk assessment data, may be useful to identify possible future PS candidates.
Nanoremediation strategies applied to contaminated river sediments can induce changes in the mobility and bioavailability of metals with potential consequences on ecosystem health. In this study, the performance of rhamnolipid (RL) coated nanoscale zero-valent iron (NZVI) in immobilizing cadmium (Cd) and lead (Pb) from contaminated river sediments was investigated. We demonstrated that RNZVI was effective in transforming labile Cd and Pb to stable fraction (the maximum residual percentage of Cd and Pb increased by 56.40% and 43.10% after 42 days of incubation, respectively), with the decrease of the mobility of metals. The increase of pH in NZVI and RNZVI treated sediment samples indicated the related mechanism for Cd and Pb immobilization. The contents of organic matter (OM) were higher than in control, with the initial addition of RL during 7 days incubation, and then the contents gradually decreased and became stable, maybe resulting from the enhancement of the activity of microorganisms and the decomposition of OM. Urease and catalase activities were enhanced with the increase of incubation time, showing certain degrees of recovery in sediment metabolic function. This work provides a new insight into the potential effects of RNZVI applications on the Cd and Pb immobilization in contaminated river sediments.
Nanoscale zero-valent iron (NZVI) has a high adsorption capacity for heavy metals, but it forms aggregates easily. In this study, zeolite-supported nanoscale zero-valent iron (Z-NZVI) was synthesized from a simplified liquid-phase reduction of iron(III) salts which simultaneously adsorbed As(III), Cd(II) and Pb(II) from aqueous solution and soil. Scanning electron micrographs showed that aggregation was eliminated and the NZVI evenly dispersed onto the surface of zeolite. FTIR spectra reveal that NZVI was protected from oxidization on the surface of Z-NZVI. XRD and XPS patterns confirmed the formation of Cd(OH) , Pb , and FeAsO in Z-NZVI after adsorption. The experimental maximum adsorption capacity of Z-NZVI was 11.52 mg As(III)/g, 48.63 mg Cd(II)/g, and 85.37 mg Pb(II)/g at pH 6, respectively, much higher than that of zeolite. Batch experiments indicate that various adsorption mechanisms including electrostatic adsorption, ionic exchange, oxidation, reduction, co-precipitation, and complexation coexisted with the selected heavy metals. Due to the formation of multiphase compounds on the Z-NZVI, the synergy and competition among heavy metals were concurrent. Most arsenic, cadmium and lead in the soil samples were immobilized after mixing with 30 g/kg Z-NZVI. These results suggest that Z-NZVI has great potential for treating water and soil multi-contaminated with heavy metals.
In this work, well-aligned ZnO nanorods were grown on the substrate of exfoliated g-C N nanosheets via a microwave-assisted hydrothermal synthesis, and then Pt/ZnO/g-C N nanostructures were obtained after the deposition of Pt nanoparticles. The growth of vertically ordered ZnO nanorods was occurred on g-C N nanosheets through the bonding interaction between Zn and N atoms, which was confirmed by XPS, FT-IR data and molecular orbital theory. The Pt/ZnO/g-C N nanostructures sensor exhibited the remarkable sensitivity, selectivity, and fast response/recovery time for air pollutants of ethanol and NO . The application of Pt/ZnO/g-C N nanostructures could be used as a dual-functional gas sensor through the controlled working temperature. Besides, the Pt/ZnO/g-C N nanostructures sensor could be applied to the repeating detection of ethanol and NO in the natural environment. The synergistic effect and improved the separation of electron-hole pairs in Pt/ZnO/g-C N nanostructures had been verified for the gas sensing mechanism. Additionally, Pt/ZnO/g-C N nanostructures revealed the excellent charge carriers transport properties in electrochemical impedance spectroscopy (EIS), such as the longer electron lifetime (τ ), higher electron diffusion coefficient (D ) and bigger effective diffusion length (L ), which also played an important role for Pt/ZnO/g-C N nanostructures with striking gas sensing activities.
A novel process on simultaneous absorption of SO and NO from flue gas using ultrasound (US)/Fe /heat coactivated persulfate system was proposed. The influencing factors, active species, products and mechanism of SO and NO removal were investigated. The results indicate that US enhances NO removal due to enhancement of mass transfer and chemical reaction. US of 28 kHz is more effective than that of 40 kHz. NO removal efficiency increases with increasing persulfate concentration, ultrasonic power density and Fe concentration (at high persulfate concentration). Solution pH, solution temperature and Fe concentration (at low persulfate concentration) have double effect on NO removal. SO is completely removed in most of tested removal systems, except for using water absorption. US, Fe and heat have a synergistic effect for activating persulfate to produce free radicals, and US/Fe /heat coactivated persulfate system achieves the highest NO removal efficiency. ·OH and SO · play a leading role for NO oxidation, and persulfate only plays a complementary role for NO oxidation.
Herein, 1,4-benzenedicarboxylate (BDC) and 2-amino-1,4-benzenedicarboxylate (NH -BDC) as organic linkers and tetraisopropyl orthotitanate as a metal source were used to synthesize several metal-organic frameworks (MOFs) nanomaterials. Five Materials Institut Lavoisiers (MILs) as MOFs include MIL-125(Ti), NH -MIL-125(Ti) and three MILs with different organic linkers molar ratios (BDC/NH -BDC: 75/25, 50/50 and 25/75 denoted as MIL-X1, MIL-X2 and MIL-X3, respectively). The synthesized nanomaterials were used for ultrasound-aided adsorption of cationic dyes (Basic Red 46 (BR46), Basic Blue 41 (BB41) and Methylene Blue (MB)) from single and multicomponent (binary) systems. The BET, XRD, FTIR, SEM, TEM, TGA and zeta potential were used for characterizing the MILs. Dye removal followed pseudo-second order kinetics with constant rate of 0.20833, 0.00481 and 0.00051 mg/g min for BR46, BB41 and MB, respectively. In addition dye adsorption obeyed the Langmuir isotherm model and the experimental dye adsorption capacity for BR46, BB41 and MB was 1296, 1257 and 862 mg/g, respectively. The synthesized MIL showed high reusability and stability over three cycles. The adsorption thermodynamics data presented that dye removal was a spontaneous, endothermic and physical reaction. The free Gibbs energy for dye removal by the NH -MIL-125(Ti) at 308K was −19.424, −15.721 and −17.413 kJ/mol for BR46, BB41 and MB, respectively.
Novel graphitic carbon nitride nanoparticles (NPs)-wrapped TiO nanotube arrays (NTAs) (g-C N /TiO ) were fabricated by a two-step method including an electrochemical anodization technique followed by impregnation under vacuum using urea as precursor. The as-prepared photoelectrode exhibited outstanding photoelectric properties and excellent photelectrocatalytic (PEC) performance for the degradation of phenol under stimulated solar light, which was due to the enhanced light absorption property and improved charge separation efficiency. The introduction of g-C N NPs strongly decreased the charge transfer resistance and boosted the charge separation efficiency of TiO . The optimum ratio of the g-C N /TiO yielded a pronounced 4.18-fold higher photocurrent density than TiO . Besides, the combination of g-C N NPs could negatively shift for the flat band potential of TiO , resulting in an enhanced reduction property for the photoelectrocatalytic degradation of organic pollutants. The PEC process for the degradation of phenol over g-C N /TiO was much higher than the sum of photocatalytic (PC) and electrocatalytic (EC) processes indicating that a photoelectric synergy was achieved on the as-prepared photoelectrode and resulting in an improved PEC performance for the composite photoelectrode.
Ag O nanoparticles-loaded Bi O I microspheres forming a three dimensional Ag O/Bi O I – heterojunction photocatalyst with wide-spectrum response were synthesized in this study. The results of transmission electron microscopy observations revealed that the Ag O nanoparticles with the diameter of 10–20 nm were distributed on the surfaces of Bi O I nanosheets. The as-synthesized Ag O/Bi O I exhibited an excellent wide-spectrum response to wavelengths ranging from ultraviolet (UV) to near-infrared (NIR), indicating its potential for effective utilization of solar energy. Compared with pure Bi O I, the Ag O/Bi O I composite also demonstrated excellent photocatalytic activity for the degradation of Bisphenol A and phenol in aqueous solution under visible LED light irradiation. Among samples, the 20% Ag O/Bi O I composite photocatalyst showed the highest photocatalytic activity for the degradation of Bisphenol A and phenol in aqueous solution. In addition, the 20% Ag O/Bi O I composite also exhibited a photocatalytic activity for the degradation of Bisphenol A under NIR light irradiation. The improved photocatalytic activity is attributed to the formation of a - heterojunction between Ag O and Bi O I, allowing the efficient utilization of solar energy (from UV to NIR) and high separation efficiency of photogenerated electron-hole pairs. The present work is desirable to explore a possible avenue for the full utilization of solar energy.
Phosphate (P) compounds are usually used as chemical amendment for remediation of heavy metal polluted sediment. However, the low deliverability, weak utilization and potential risk of eutrophication inhibit the application of most P materials. Therefore, rhamnolipid (Rha), a kind of anionic biosurfactant which has algicidal activity, was employed in this study to synthesize a new kind of nano-chlorapatite (nClAP) for Pb and Cd immobilization. Characterization results showed that the Rha stablized nClAP (Rha-nClAP) was uniformly distributed in suspensions within about 5 nm. Experimental data demonstrated that the combination of Rha and nClAP could greatly enhance the Pb- and Cd-immobilization efficiencies, promoting their transformation from labile fractions to stable fractions through precipitation or adsorption processes, especially when the Rha approached to its critical micelle concentration. And Rha-nClAP could also decrease both the TCLP-leachable Pb and Cd with maximum reduction efficiencies of 98.12% and 96.24%, respectively, which also presented concentration dependence of Rha. Changes of available phosphorus implied the dissolution of nClAP during the treatment and the detection of organic matter demonstrated that the microorganisms may involve in the remediation.
Materials of perovskite-type structure have attracted considerable attention for their applications in photocatalysis. In this study, a novel composite of -type LaFeO microsphere coated with -type nanosized graphitic carbon nitride nanosheets was constructed by the quasi-polymeric calcination method with the aid of electrostatic self-assembly interaction. Results indicate that the LaFeO /g-C N - heterostructured photocatalyst obtained, in contrast to the pure constituents, enabled improved visible-light absorption, and more efficient separation and migration of charge carriers solid - heterojunction interfacial effect. Correspondingly, the LaFeO /g-C N composite allowed for higher visible-light-responsive photocatalytic activity for the degradation of Brilliant Blue, which was 16.9 and 7.8 times that of pristine g-C N and LaFeO , respectively. The photocatalytic degradation of Brilliant Blue was ascribed to the combined contributions of the photogenerated holes (h ), superoxide radicals ( O ) and hydroxyl radicals ( OH). Based on solid heterojunction interfacial interaction, a Z-scheme charge carrier transfer pathway integrated with the dye-sensitization effect is proposed as the underlying mechanism of the photocatalytic reaction process. Therefore, we believe that the perovskite-type LaFeO /g-C N Z-scheme photcatalyst promotes the development of photocatalysis and holds much promise for environmental remediation.
A novel Fenton-like catalyst (Zn-Fe-CNTs) capable of converting O to H O and further to OH was prepared through infiltration fusion method followed by chemical replacement in argon atmosphere. The catalyst was characterized by SEM, EDS, TEM, XRD and XPS. The reaction between Zn-Fe-CNTs and O in aqueous solution could generate H O in situ, which was further transferred to OH. The Fenton-like degradation of sulfamethoxazole (SMX) using Zn-Fe-CNTs as catalyst was evaluated. The results indicated that Zn-Fe-CNTs had a coral porous structure with a BET area of 51.67 m /g, exhibiting excellent adsorption capacity for SMX, which enhanced its degradation. The particles of Zn and Fe /Fe O were observed on the surface of Zn-Fe-CNTs. The mixture of Zn and CNTs could reduce O into H O by micro-electrolysis and Fe /Fe O could catalyze in-situ generation of H O to produce OH through Fenton-like process. When initial pH = 1.5, T = 25 °C, O flow rate = 400 mL/min, Zn-Fe-CNTs = 0.6 g/L, SMX = 25 mg/L and reaction time = 10 min, the removal efficiency of SMX and TOC was 100% and 51.3%, respectively. The intermediates were detected and the possible pathway of SMX degradation and the mechanism of Zn-Fe-CNTs/O process were tentatively proposed.
Toxic heavy metal containing Cr(VI) species is a serious threat for ecological environment and human beings. In this work, a new mussel-inspired polydopamine microsphere (PDA-sphere) is prepared through oxidative polymerization at air condition with controllable sizes. The adsorption of Cr(VI) ions onto PDA-sphere is highly pH dependent with the optimal pH ranging from 2.5 to 3.8. A rapid Cr(VI) removal can approach in 8 min for equilibrium. More importantly, the prepared materials exhibit a remarkable sorption selectivity, coexisting SO , NO and Cl ions at high levels; The applicability model further proves its effective performances with treated capacity of 42,000 kg/kg sorbent, and the effluent can be reduced from 2000 ppb to below 50 ppb, which meets the drinking water criterions recommended by WHO. 1 kg sorbent can also purify approximately 100 t Cr(VI) contaminated wastewaters basing on the wastewater discharges of China. Such capacity for application ranks the top level for Cr(VI) removal. Additionally, the exhausted materials can be well regenerated by binary alkaline and salts mixtures. Such efficient adsorption can be ascribed to the well-dispersed morphology as well as the strong affinity between Cr(VI) and catechol or amine groups by XPS investigation. All the results suggest that polydopamine microspheres may be ideal materials for Cr(VI) treatment in waters.
To realize the full utilization of solar energy, the design of highly efficient photocatalyst with improved visible-near-infrared photocatalysis performance has attracted great attentions for environment pollutant removal. In this work, we rationally employed the surface plasmon resonance effect of metallic Ag in the phosphorus doped ultrathin g-C N nanosheets (PCNS) and BiVO composites to construct a ternary Ag@PCNS/BiVO photocatalyst. It was applied for the photodegradation of ciprofloxacin (CIP), exhibiting 92.6% removal efficiency under visible light irradiation (λ > 420 nm) for 10 mg/L CIP, and presenting enhanced photocatalytic ability than that of single component or binary nanocomposites under near-infrared light irradiation (λ > 760 nm). The improved photocatalytic activity of the prepared Ag@PCNS/BiVO nanocomposite can be attributed to the synergistic effect among the PCNS, BiVO and Ag, which not only improves the visible light response ability and hinders the recombination efficiency of the photogenerated electrons and holes, but also retains the strong the redox ability of the photogenerated charges. According to the trapping experiment and ESR measurements results, OH, h and O all participated in the photocatalytic degradation process. Considering the SPR effect of metallic Ag and the established local electric field around the interfaces, a dual Z-scheme electrons transfer mechanism was proposed.
It has been clearly demonstrated that the visible-light photocatalytic activities of g-C N (CN) for degrading 2,4-dichlorophenol (2,4-DCP) and bisphenol A (BPA) could be improved by fabricating nanocomposites with a proper amount of nanocrystalline anatase TiO . Interestingly, the visible-light activities of the amount-optimized nanocomposite could be further improved after decorating Au nanoparticles, with 5.11- and 3.1-time improvement respectively for 2,4-DCP and BPA compared to that of CN, even much higher than that of P25 TiO under UV–vis irradiation. Based on the transient-state surface photovoltage responses and photoelectrochemical measurements, it is confirmed that the exceptional visible-light activities of the fabricated Au-(TiO /g-C N ) nanocomposites are attributed to the extended visible-light response due to the surface plasmonic resonance (SPR) of decorated Au and its catalytic function, and to the enhanced charge separation by transferring electrons from CN and SPR Au to TiO in the nanocomposites. The highly promoted charge separation results in the effective availability of a large number of hydroxyl radicals ([rad]OH) participating in the photocatalytic oxidation process of 2,4-DCP. Furthermore, a possible mechanism of 2,4-DCP degradation is proposed according to the detailed analyses of produced intermediates. This work provides new idea for designing Au assisted nanocomposite photocatalysts for environmental remediation.
A novel method was developed and applied for the treatment of simulated wastewater containing multiple heavy metals. A sorbent of ZnS nanocrystals (NCs) was synthesized and showed extraordinary performance for the removal of Hg , Cu , Pb and Cd . The removal efficiencies of Hg , Cu , Pb and Cd were 99.9%, 99.9%, 90.8% and 66.3%, respectively. Meanwhile, it was determined that solubility product ( ) of heavy metal sulfides was closely related to adsorption selectivity of various heavy metals on the sorbent. The removal efficiency of Hg was higher than that of Cd , while the of HgS was lower than that of CdS. It indicated that preferential adsorption of heavy metals occurred when the of the heavy metal sulfide was lower. In addition, the differences in the of heavy metal sulfides allowed for the exchange of heavy metals, indicating the potential application for the sequential removal and separation of heavy metals from wastewater. According to the cumulative adsorption experimental results, multiple heavy metals were sequentially adsorbed and separated from the simulated wastewater in the order of the of their sulfides. This method holds the promise of sequentially removing and separating multiple heavy metals from wastewater.
Aerobic composting is used widely for animal manure recycling, and it may reduce the amount of antibiotic resistance genes (ARGs) that enter the environment. We sampled three types of animal (bovine, chicken, and pig) manure and the corresponding composts from 12 large-scale farms, and tested multiple ARGs and mobile genetic elements (MGEs) by high-throughput qPCR. A total of 109 ARGs were detected in the manure and compost samples, thereby demonstrating that both are important ARG reservoirs. The diversity and abundance of ARGs were significantly higher in chicken and pig manure than bovine manure, but industrial composting was more efficient at reducing the ARGs in chicken manure than pig and bovine manure. Composting universally reduced some ARGs, but inconsistently influenced other ARGs from different types of animal manures. Network analysis detected the widespread co-occurrence of ARGs and MGEs. , , , ( ) ( ), and were identified as suitable indicator genes for estimating the total abundance of ARGs. Our results suggest that different animal species had significant effects on the diversity, abundance, and persistence of ARGs, where the abundance of transposons, heavy metal concentration, total nitrogen level, and the dosage and duration of exposure to antibiotics may explain these differences.
A novel water-compatible surface molecularly imprinted thiol-functionalized titanium dioxide (TiO ) material (CMIP-coated TiO ) was prepared in water, using 2, 4-dinitrophenol (2, 4-DNP) as template molecule and -phenylenediamine (OPDA) as both functional monomer and cross-linker. The as-synthesized materials were characterized by FESEM, FTIR, XRD, BET and UV–vis DRS. Moreover, we have investigated the adsorption capacity, adsorption selectivity and photodegradation activity of the CMIP-coated TiO and non-molecular imprinted materials (CNIP-coated TiO ). Additionally, the effects of pH and concentration of 2, 4-DNP on the degradation rate of 2, 4-DNP were also investigated. Results showed that CMIP-coated TiO exhibited higher adsorption capacity, greater selectivity and faster photodegradation activity for 2, 4-DNP compared with the CNIP-coated TiO . Meanwhile, the specific selectivity to 2, 4-DNP over its structural analogue 4-nitrophenol (4-NP) and the enhanced photodegradation capacity were mainly attributed to the imprinted cavities on the surface of CMIP-coated TiO . Taking advantage of efficient removal capacity, high reusability and no-additional chemicals in imprinted process, the prepared materials can be potentially applied to “green” removal of 2, 4-DNP in wastewater.
The development of efficient solar driven catalytic system for the degradation of antibiotics has become increasingly important in environmental protection and remediation. Non-noble-metal NiS and MoS nanosheet co-modified graphitic C N ternary heterostructure has been synthesized via a facile combination of hydrothermal and ultrasound method, and the ternary heterostructure has been utilized for photocatalytic degradation of antibiotic agents. The antibiotics of ciprofloxacin (CIP) and tetracycline hydrochloride (TC) were photodegraded by the hybrid under the visible light. The optimal photodegradation rate of the ternary heterostructure reaches about 96% after 2 h irradiation, which is 2.1 times higher than that of pure g-C N for TC degradation. The photocatalytic degradation rates of the ternary heterostructure for both CIP and TC obey the pseudo-first-order kinetic model. The enhanced visible light adsorption and charge separation efficiency contribute to the photocatalytic performance of the ternary heterostructure. This work provides new insights and pathways by which efficient degradation of antibiotics can be achieved and will stimulate further studies in this important field.
The animal experiment was preformed to investigate the roles of PPAR-γ/PI3K/Akt pathway in apoptosis triggered by cadmium (Cd) and in the antagonistic effects of selenium (Se) on Cd in the pancreas of chicken. The current study showed that Cd treatment obviously increased the accumulation of Cd and directly led to lower activities of amylase, trypsin and lipase in chicken pancreas. The expression of PPAR-γ, PI3K, and Akt was declined, whereas the level of Bax, Cyt C and caspase-3 were increased in Cd group. In the result of TUNEL assay and the histological examination, typical apoptosis characteristics in the pancreas of Cd group were confirmed. Cd group also showed high levels of inducible nitric oxide synthase (iNOS) activity and nitric oxide (NO) content in pancreas. However, those Cd-induced changes were obviously alleviated in Cd + Se group. Our study revealed that Cd could impact the pancreas function and induce the activation of and the overproduction of NO via PPAR-γ/PI3K/Akt pathway to promote apoptosis in chicken pancreas. However, Se could reduce Cd accumulation and antagonize Cd-triggered apoptosis in chicken pancreas.