Inter-zonal Tradable Discharge Permit System to Control Water Pollution in Tianjin, China

In recent years, Chinese environmental authorities have expressed interest in the use of Tradable Discharge Permits (TDP) as a regulatory instrument to control pollutant emissions. Environmental professionals still have not had enough experience, however, in designing and managing TDP systems, especially for non-uniformly dispersed pollutants. As an empirical study, this paper proposes an inter-zonal TDP system and analyzes its effectiveness in cost savings and environmental protection for reducing water pollutant COD (chemical oxygen demand) in Tianjin, China. Zonal permit system (ZPS) and emission permit system (EPS) are discussed for comparison. The inter-zonal TDP system is demonstrated to improve cost efficiency by allowing permit trades between zones, as long as water quality constraints are satisfied. The transactions are assumed to proceed in a multilateral sequential way and are simulated with a circularly running linear programming (LP) model. The simulation of permit transactions among 20 firms shows that to reach the same COD removal target, ZPS, inter-zonal TDP system, and EPS lowered the total reduction cost by 12.8%, 14.6%, and 15.8%, respectively. EPS, however, brought about “hot spots” problem. Finally, the transaction costs and the sensitivity of the three TDP systems to changes in both COD reduction rate and the initial permit allocation are discussed, and policy implications are addressed

GO–Polymer Modified Anion Exchange Membranes for Antifouling

Organic fouling was one of key issues limiting the application of electrodialysis in the treatment of industrial wastewater, which results in degradation of membranes and high energy consumption. In this study, a novel graphene oxide (GO)–polymer modified anion exchange membrane (AEM) for antiorganic fouling was first developed by layer-by-layer interfacial polymerization (IP). The surface of AEM was alternately contacted with GO and tannic acid (TA) aqueous as the water phase and an n-hexane solution of trimesoyl chloride (TMC) as the organic phase; thus, a multilayer GO–polymer structure was fabricated on the surface of AEM. Results showed that the aqueous phase was preferred to be the final treatment of layer-by-layer interfacial polymerization, which was more conducive to enhancing hydrophilicity and negative charge density of the membrane surface. Compared with TA-TMC modified AEM, the introduction of GO nanosheets with carboxyl groups into aqueous solution significantly increased the negative charge density of the membrane surface and reduced membrane resistance. The desalination rate of (GOTA-TMC)1.5 was mostly close to that of pristine AEM without fouling, exhibiting significant antifouling performance and good stability. The study provides promising insights into the modification of ion exchange membranes with functional materials and a polymer composite layer

Selective Production of Jet-Fuel-Range Alkanes from Palmitic Acid over Ni/H-MCM-49 with Two Independent Pore Systems

With two independent pore systems (intralayer sinusoidal channels and interlayer supercages) and external 12 membered-ring (MR) cups, H-MCM-49 was selected as the acidic support for upgrading palmitic acid to jet-fuel-range hydrocarbons via simultaneous hydro-deoxygenation, hydrocracking, and hydroisomerization. Compared to other zeolites, H-MCM-49 showed better selectivity toward cracking and isomerizing products (C12–C14 alkanes). Postsynthesis of H-MCM-49 could tailor acidity and catalytic performance to produce more C12–C14 cracking and isoalkane products. Ni/H-MCM-49 bifunctional catalysts restrained the acid-catalyzed reactions to some extent because of enhancement in hydro-deoxygenation over Ni particles, leading to the decrease in appropriate cracking of C12–C14 alkanes’ and isoalkanes’ selectivity. Ni/H-MCM-49 bifunctional catalysts exhibited excellent catalytic stability on activity and selectivity of target products, which opened a novel tailoring pathway over zeolites with independent pore systems

Degradation of Sulfamethoxazole by Manganese(IV) Oxide in the Presence of Humic Acid: Role of Stabilized Semiquinone Radicals

In this work, we demonstrate for the first time the abatement of sulfamethoxazole (SMX) induced by stabilized ortho-semiquinone radicals (o-SQ•–) in the MnO2-mediated system in the presence of humic acid. To evaluate the performance of different MnO2/mediator systems, 16 mediators are examined for their effects on MnO2 reactions with SMX. The key role of the bidentate Mn(II)-o-SQ• complex and MnO2 surface in stabilizing SQ•– is revealed. To illustrate the formation of the Mn(II)-o-SQ• complex, electron spin resonance, cyclic voltammetry, and mass spectra were used. To demonstrate the presence of o-SQ• on the MnO2 surface, EDTA was used to quench Mn(II)-o-SQ•. The high stability of o-SQ•– on the MnO2 surface is attributed to the higher potential of o-SQ•– (0.9643 V) than the MnO2 surface (0.8598 V) at pH 7.0. The SMX removal rate constant by different stabilized o-SQ• at pH 7.0 ranges from 0.0098 to 0.2252 min–1. The favorable model is the rate constant ln (kobs, 7.0) = 6.002EHOMO(o-Qred) + 33.744(ELUMO(o-Q) – EHOMO(o-Qred)) – 32.800, whose parameters represent the generation and reactivity of o-SQ•, respectively. Moreover, aniline and cystine are competitive substrates for SMX in coupling o-SQ•–. Due to the abundance of humic constituents in aquatic environments, this finding sheds light on the low-oxidant-demand, low-carbon, and highly selective removal of sulfonamide antibiotics

Highly Selective PdCu/Amorphous Silica−Alumina (ASA) Catalysts for Groundwater Denitration

Catalytic nitrate reduction is a promising technology in groundwater purification. In this study, PdCu bimetallic catalysts supported on an industrial amorphous silica−alumina (ASA) were synthesized and used to simulate catalytic removal of nitrate in groundwater. The catalysts exhibited very high activity and the highest catalytic selectivity toward N2O and N2 was 90.2%. The optimal Pd/Cu weight ratio was four. Relatively low reduction temperature was found benefit the catalytic stability and 300 °C was the appropriate reduction temperature during catalyst preparation. With an average particle size 5.4 nm, the metal particles were very uniformly distributed on the catalyst surface prepared with the codeposition method. This kept the catalyst more stable than the PdCu/Al2O3 catalyst with larger metal particles. According to XRD, TEM, and XPS results, the metals maintained zero-valence but aggregated by about 2 nm during the denitration reaction, which caused gradual deactivation of the catalysts. Little leaching of Cu and Pd from the catalyst might also have a slightly negative impact to the stability of the catalysts. A simple treatment was found to redistribute the particles on the deactivated catalysts, and high catalytic activity was recovered after this process

Unexpectedly Enhanced Organics Removal in Persulfate Oxidation with High Concentration of Sulfate: The Origin and the Selectivity

Massive anions in high saline wastewater are primary factors that restricted the efficiency of pollutant degradation in advanced oxidation processes (AOPs). Herein, we reported the influence laws of different anions at high concentration on the electron-transfer process in the activation of persulfate, and especially, the sulfate anion exhibited the excellent promotion effect. Depending on the ionic charge, polarizability, and size, the anions exerted diverse effects on the dispersed phase and zeta potential of carbonaceous catalysts, which further embodied in the removal of pollutants. Based on the differences of reaction rate constant in water solution and high saline solution, the order was ClO4– 3– – 42– 32–, obeying the Hofmeister series. The enhancement of the sulfate anion was widely confirmed with different carbonaceous catalysts and pollutants with various structures. It could be attributed to the higher oxidation capacity, the faster interfacial electron transfer, and the better catalyst dispersion in the high sulfate environment. On the other hand, the decrease of zeta potential of the catalyst induced by sulfate reinforced the electrostatic attraction or repulsion with pollutants, which caused the selectivity of the sulfate promotion effect. Overall, this study provides new insights into the mechanism of influence of anions on AOPs, which refreshed the cognition of the role of sulfate on pollutant degradation, and helps guide the treatment design of high salinity wastewater

High-Performance Recovery of Vanadium(V) in Leaching/Aqueous Solution by a Reusable Reagent-Primary Amine N1519

Efficient extraction and stripping for recovering vanadium­(V) from the leaching/aqueous solution of chromium-bearing vanadium slag (V–Cr slag) are essential to the reuse of heavy metals. The performance characteristics of a new reagent, primary amine N1519, were first reported for extracting vanadium. With a phase ratio of organic to aqueous up to 1:1, 99.7% of vanadium­(V) can be effectively extracted from the leaching/aqueous solution, and powder of NH₄VO₃ was obtained through the stripping with ammonia. The new reagent can be recyclable in use for sustainable reuse after stripping. Different extraction conditions, e.g., the initial pH of the leaching/aqueous solution and the molar quantity of N1519 were investigated. The powder of vanadium-organic compounds (VOC) with N1519 formed in the process of extraction was obtained and purified through three-steps of solvent-out crystallizations. The hydrogen bond association mechanism of extraction was illustrated with the structure of VOC and the enthalpy change in extraction process. The fast extraction process and slow stripping procedure for recovering vanadium­(V) are suitable for use in annular centrifugal contactors with very short contact/resident times and mixed-settler extractors with very good mass transfer, respectively. The results offer significant advantages over conventional processes

Open-Framework Metal Oxides for Fast and Reversible Hydrated Zinc-Ion Intercalation

The development of high capacity and stable cathodes is the key to the successful commercialization of aqueous zinc-ion batteries. However, significant solvation penalties limit the choice of available positive electrodes. Herein, hydrated intercalation is proposed to promote reversible (de)­intercalation within host materials by rationally designing a matching electrode. In contrast to previously reported works, the as-prepared electrode (NHVO@CC) can achieve fast and reversible intercalation of hydrated zinc ions in the interlayer gap, leading to a high capacity of 517 mAh g–1 at 0.1 A g–1 and excellent electrode stability for long-term cycling. Besides, as a consequence of the flexibility of the NHVO@CC electrode, a quasi-solid-state battery was achieved with equally advantageous electrochemical behavior under various bending states. The proposed hydrated cation direct insertion/extraction sets up an efficient way of developing high-performance positive electrodes for aqueous batteries