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A great paradigm for state-of-the-art biomaterials is to use renewable lignocelluloses with ionic liquid-based green regimes. Novel transparent films were successfully prepared from the purified eucalyptus cellulose by the moderate incorporation of gutta percha (GP, 5–15%) using 1-butyl-3-methylimidazolium acetate ([bmim]OAc) as a versatile solvent. The refined GP was obtained from Eucommia ulmoides Oliver after hot-water extraction, alkaline treatment, enzymatic hydrolysis, and extended petroleum ether purification. The cellulose/GP films exhibited a well-distributed and smooth structure, and the crystalline structure of composite films was transformed from cellulose I to II. The incorporation of 5–10% GP obviously improved the tensile strength of films (129–139 MPa) as compared to the pure cellulose film (81 MPa). Moreover, the novel hybrid films showed excellent thermal stability and oxygen barrier property as a result of the reinforcement by GP. The cellulose/GP films with prominent tensile strength, thermal stability and oxygen permeability could be tuned via varying the ratio of GP to cellulose matrix, which can be exploited as a potential candidate of pollution-free, biodegradable and renewable cellulose-based composites for the substitute of petroleum derived packaging materials.

Sustained molecular oxygen activation by iron doped silicon carbide (Fe/SiC) was investigated under microwave (MW) irradiation. The catalytic performance of Fe/SiC for norfloxacin (NOR) degradation was also studied. Rapid mineralization in neutral solution was observed with a pseudo-first-order rate constant of 0.2239 min −1 under 540 W of MW irradiation for 20 min. Increasing Fe/SiC rod and MW power significantly enhanced the degradation and mineralization rate with higher yield of reactive oxygen species (ROS). Fe shell corrosion and subsequent Fe 0/II oxidation by molecular oxygen with MW activation was the key factor for NOR degradation through two-electron-transfer by Fe 0 under acidic conditions and single-electron-transfer by Fe II under neutral-alkaline solution. Removal rate of NOR was significantly affected by solution pH, showing higher degradation rates at both acidic and alkaline conditions. The highest removal efficiencies and rates at alkaline pH values were ascribed to the contribution of bound Fe II species on the Fe shell surface due to the hydroxylation of Fe/SiC. ·OH was the main oxidizing specie for NOR degradation, confirmed by density functional theory (DFT) calculations and radical scavenger tests. DFT calculations were conducted on the reaction/activation energies of the transition/final states of NOR/degradation products, combined with intermediate identification with high performance liquid chromatography coupled with a triple-quadruple mass spectrometer (HPLC-MS/MS), the piperazinyl ring was the most reactive site for ·OH attack, followed by further ring-opening and stepwise oxidation. In this study, Fe/SiC were proved to be an excellent catalyst for the treatment of fluoroquinolone antibiotics with MW activation.

In this work, a hierarchical Ni3S2@MoS2 hybrid structure was synthesized by an effective strategy with a combined hydrothermal route and subsequent annealing treatment. When tested as supercapacitor electrodes, the Ni3S2@MoS2 composites exhibited high specific capacitance of 1418.5 F g−1 at 0.5 A g−1, which also showed a good capacitance retention of 75.8% at 5 A g−1 after 1250 cycles. The Ni3S2@MoS2 composites demonstrated 1.9 fold higher specific capacitance compared to the amorphous shell counterpart (NixSy@MoS2). Furthermore, the assembled asymmetric supercapacitor (Ni3S2@MoS2//rGO) also demonstrated a capacitance of 61 F g−1 at 0.5 A g−1, with energy and power densities of 21.7 Wh kg−1 at 400 W kg−1 and 12 Wh kg−1 at 2400 W kg−1 under an operating window of 1.6 V. The asymmetric supercapacitor also showed a favorable cycle stability with 72% capacity retention over 4000 cycles at 10 A g−1. The improved electrochemical performance is attributed to the synergetic effect of the large accessible surface area and optimal contacts between the MoS2 and the electrolyte, as well as high capacitance of the metallic Ni3S2 core.

Geopolymer has been demonstrated as a promising candidate to replace Portland cement with less carbon footprint and energy consumption. The practical application of geopolymers is largely relying on strength development via the geopolymerization process. The application of microwave (MW) as an efficient auxiliary processing technology for geopolymers manufacture is emerging. Here in this paper, the fundamental mechanisms, influencing factors, and the potentials of microwave in geopolymer applications were reviewed. The capability of volumetric heating could generate significantly different heating patterns from traditional heating, therefore greatly reducing the processing time and enhancing the mechanical strength. The selective heating of certain ingredients with different dielectric properties would also benefit the immobilization of heavy metals in the geopolymer network, therefore facilitate solid waste disposal and recycle with significant environmental benefit. The current development of the promising microwave-assisted geopolymer strategy is mainly limited by the lack of large-scale microwave reactors. Future efforts to increase the energy conversion efficiency and processing capacity of MW reactors are critical before large-scale industrial applications.

Tin-containing slag from pyrometallurgical recovery process of spent lead-acid battery is a valuable secondary Sn resource. However, the low content of Sn (~4 wt%) in this slag with complex impurities (Fe, Al, Pb, Zn, and Cu, etc.) makes it challenging for efficient tin separation. In this study, a low-temperature chlorinating process is proposed for tin recovery from the tin-containing slag by using ammonium chloride as the chlorinating reagent. Under the optimized chlorinating conditions, tin volatilization ratios of above 96% under both air and vacuum atmospheres could be achieved. However, the discrepancy between the temperatures of tin chlorinating and impurity metal chlorinating is more dramatic under the air atmosphere than that under vacuum, which facilitates the separation of impurities. Meanwhile, the decomposition rate of NH4Cl in air is much lower than that under vacuum atmosphere, resulting in less consumption of NH4Cl. The obtained chlorinated condensation product in air is subjected to a subsequent water leaching-alkali smelting-leaching-crystallization process to effectively separate Fe impurity and obtain the final sodium stannate product with a total tin recovery ratio of 94%. This study provides a promising strategy for the recovery of tin, and significant environmental benefit could be generated simultaneously with solid waste recycling.

The electrogeneration of H2O2 and electro-regeneration of ferrous are conflicting matters in electro-Fenton system. In this research, the degradation of Rhodamine B, methyl orange (MO) and 4-chlorophenol (4-CP) was investigated using a novel dual-cathode microbial fuel cell (MFC) electro-Fenton (EF) hybrid system. An air-cathode of an EF system was used for H2O2 electrogeneration and a carbon felt cathode of a MFC was used to accelerate Fe2+ regeneration. Synergistic improvement of MFC power generation and the degradation of the above refractory organics through EF reaction was achieved. The EF air-cathode was fabricated by adopting activated carbon/graphite powder mixture and PVDF binder, which showed higher H2O2 generation but slower Fe3+ reduction rate than MFC carbon felt cathode. The Rhodamine B removal rate constant and mineralization current efficiency of the MFC coupled EF were 64% and 42% higher than that of uncoupled EF, respectively. The MFC-EF coupled system also exhibited significantly higher removal efficiency for MO and 4-CP than that of un-coupled EF system. Moreover, the power density of MFC was greatly enhanced by coupling EF due to higher Fe3+/Fe2+ redox potential than oxygen reduction.

Hybrid organic-inorganic perovskite is a class of emerging materials with promising application prospects in optoelectronics. However, the consumption of lead resources and poor stability in moisture environment have limited their practical applications. Herein, a family of air-stable two-dimensional (2D) hybrid organic-inorganic perovskite crystal (C4H9NH3)2PbX4 (X=Cl, Br, I or mixed halides of them) is efficiently synthesized by direct recovery of spent lead-acid battery (LAB) paste. More than 95 wt% of the total lead element in spent lead paste could be recovered and converted into low-impurity lead ion solution via a facile recovery process at room temperature. Then 2D hybrid perovskite crystal is synthesized from the recovered lead ion solution with a one-pot solvent evaporation method. Excellent air stability is observed for the prepared perovskite crystals after exposure in high-humidity air at a high temperature of 75 °C, attributing to its layered structure which is capped with long-chain hydrophobic alkyl groups. The emission wavelengths of the synthesized perovskite crystals are tunable from 380 to 560 nm (corresponding to visible purple to yellow light) by compositional modulations, demonstrating their potential applications as optoelectronic materials. This research has proposed a promising strategy to synthesize high-value 2D hybrid perovskite optoelectronic materials directly recovered from spent LAB.

Phosphorus (P) recovery from incinerated sewage sludge ash (ISSA) has attracted increasing attentions in recent years. In this study, the P recovery was comparatively investigated on two types of ISSA for sewage sludge pretreated by Fenton's reagent, and a composite conditioner of Fenton's reagent and lime (referred to as ISSA-F and ISSA-FL, respectively). ISSA derived from raw sludge (referred to as ISSA-RS) was studied as the control group. The P species results showed that the proportions of AP (Ca-bound P) and NAIP (Al/Fe-bound P) in the ISSA samples were significantly affected by the added Fe and Ca elements in the sludge conditioner. The order of leaching efficiency of P in different ISSA samples was ISSA-F (100%) > ISSA-RS (94.4%) > ISSA-FL (83.1%), which was significantly related to the Ca content in those ISSA samples. Higher Ca content in the ISSA-RS and ISS-FL samples induced calcium oxalate precipitation during leaching process, which hindered the release of P from ISSA. P recovery product mainly composed of aluminum hydroxyphosphate was prepared from the purified solutions leached from different ISSA samples. Moreover, acid-leaching residues of different ISSA samples after P recovery were proposed to be reutilized as cement mortar additives by replacing 15 wt% of cement. The mechanical strength of the test cement mortar specimens with acid-leaching residues was comparable to that of the control cement mortar specimen without residue.

This study investigated the synergistic effect of water content and a composite conditioner of Fenton's reagent combined with red mud (Fenton-RM) on the pyrolytic products (fuel gas, tar, and solid char) of deep-dewatered sludge. The catalytic effect of metal oxides in Fenton-RM could be promoted by the presence of water during sludge pyrolysis, showing higher gas yield with increased water content. Maximum gas outputs of the deep-dewatered sludge conditioned with Fenton-RM (S-Fenton-RM) and the conventional dewatered sludge conditioned with polyacrylamide (S-PAM), both appeared at 900 °C with a water content of 65 wt%, and were 0.257 and 0.189 L/g dry solid (DS), respectively. At the same temperature and with the same water content, the hydrogen (H2) yields of the S-Fenton-RM samples were always higher than those of the S-PAM samples. At 900 °C, the maximum H2 yield of the S-Fenton-RM samples was 0.102 L/g DS, which was 85.5% higher than that of the S-PAM samples. The results indicated that water in the wet sludge provided the steam atmosphere for pyrolysis, and the water vapor then involved in secondary cracking reformation of tar and char gasification reactions, which would be catalyzed by the presence of metal oxides in the Fenton-RM conditioner, thus increasing the yield of fuel gas, especially hydrogen. The H2 production cost from the S-Fenton-RM system is less than that from the S-PAM system. The results suggest that pyrolysis of the wet deep-dewatered sludge conditioned with Fenton-RM is an economical and promising alternative for sewage sludge dewatering and disposal/reuse.

The catalytic capabilities of copper doped attapulgite (Cu/ATP) and silicon carbide (Cu/SiC) nanocomposites for p-nitrophenol (PNP) were characterized under microwave (MW) irradiation. Higher catalytic performance of Cu/SiC was obtained than that of Cu/ATP due to higher production rate of reactive oxygen species (ROS) as well as higher MW absorptivity. The electron (e−) – hole (h+) pairs were related to the generation of ROS on Cu/SiC. The modification Cu with SiC had an enhancement on the band gap and large EVB absolute values, which promoted the catalytic activity of Cu/SiC. An ROS-producing copper-redox cycle between CuI and CuII of Cu/ATP was responsible for PNP degradation. The produced CuI via thermal dissociation of [Cu–O–Cu]n species in Cu/ATP activated molecular oxygen, followed by Fenton-like reactions to produce ROS. The reusability of the catalysts and negligible phase transformation of Cu species after five rounds of cycle verified the catalyst stability. Based on Density functional theory (DFT) calculation and catalytic experimental analyses, the denitro-hydroxylation of PNP was the initial oxidation reaction step followed by further oxidation to form short-chain carboxylic acids. OH oxidation was predominant whereas O2− was not involved in the OH addition on the meta-position due to lower oxidation energy than the corresponding activation energies. Other than reactive species attack, the “hot spots” on the surface of Cu/SiC was responsible for thermal stabilization of PNP/intermediates in soil. In this study, MW-assisted Cu/ATP and Cu/SiC catalytic degradation of PNP was proved to be an efficient technology for wastewater treatment and soil remediation.

Two-dimensional accordion-like alk-Ti 3 C 2 was prepared by acid etching and alkaline intercalation treatment, and demonstrated as a new platform for the simultaneous electrochemical detection toward multiple heavy metal ions using square wave anodic stripping voltammetry. The alk-Ti 3 C 2 modified electrode exhibited significantly improved electrochemical response in comparison with the Ti 3 C 2 modified electrode due to the unique morphology and surface chemistry characteristics. Key operational parameters including pH, deposition potential and deposition time were optimized for the determination of trace heavy metal ions. Under the optimum conditions, it exhibited a high sensitivity superior to most of reported values and good linear correlations, with a detection limit of 0.098 μM, 0.041 μM, 0.032 μM and 0.130 μM for Cd(II), Pb(II), Cu(II) and Hg(II), respectively. Furthermore, mutual interference among the four target metal ions was explored, and the preferential deposition of Pb(II) in the presence of other three metal ions together with an enhanced Hg(II) sensitivity in the presence of Cd(II) were discovered. This method offers a new strategy for heavy metal detection using MXenes materials.

The migration of long chain soluble lithium polysulfides through the separator to the anode, the so called “shuttle effect”, is one of the major issues responsible for the capacity degradation of lithium-sulfur (Li-S) batteries. In this work, N and S co-doped mesoporous carbon was prepared by a novel egg shell template method and utilized to modify the separator for high performance Li-S batteries. The discharge capacity of the second cycle retained at 1467 mAh g −1 at 1 C after 200 cycles and decayed at 0.20% per charge-discharge cycle, and a reversible capacity of 561 mAh g −1 was achieved even at 5 C rate after 200 cycles. The prepared material showed a porous hollow sphere morphology with larger surface area and N and S co-doped that can provide great electrochemical property as well as surface chemistry for the adsorption of the intermediate polysulfides. After separator modification, XPS analysis revealed that pyrrolic-type N, pyridinic-like N, and thiosulphate were the major factors contributing to the superior electrochemical performance of the CS/S cathode. This work also provided a rational design strategy for the modification of separator to effectively utilize the active sulfur and to retard the migration of dissolved polysulfides, which enhanced the performance of high energy density Li-S batteries with long cycling life.

The integrated biorefinery of woody biomass for the synthesis of cellulose materials and hemicellulosic products is nowadays considered attractive towards a sustainable standpoint. The effects of alkaline, hydrothermal and acidic pretreatments on the preparation of regenerated cellulose fibers from eucalyptus via ionic liquid wet-spinning, and the isolation and conversion of hemicelluloses using different pretreatments were explored. The structure of alkali-soluble hemicelluloses via 5% sodium hydroxide extraction was deduced to be D-Glc p -4- O -methyl- d -glucurono- d -xylan. The xylooligosaccharides (XOS, DP 2–6) yields by hydrothermal (180 °C, 30 min) and 0.25 mol/L dilute sulphric acid (90 °C, 1 h) pretreatments were 37.30 and 52.12 mg/g respectively, and the main XOS productions were xylobiose (11.19–15.68 mg/g) and xylotriose (10.03–11.63 mg/g). The isolated cellulose could be completely dissolved in 1-butyl-3-methylimidazolium acetate ([bmim]OAc) and the chemical conformation of the regenerated fibers was similar to cellulose II. The viscosity of the spinning dopes, the morphology, molecular weights and mechanical strength of the fibers were highly dependent on the type of pretreatments. The multifilament fibers exhibited a smooth morphology and good mechanical property (1.55–2.01 cN/dtex) being close to commercial viscose rayon. The conversion of hemicelluloses to value-added products was achieved via different pretreatments in conjugation with cellulose spinning process.

Electro-dewatering (EDW) is an innovative method for volume reduction of sewage sludge before re-utilization and disposal. In this study, dewaterability limit and energy consumption in sludge electro-dewatering process were directly explored using in-situ linear sweep voltammetry (LSV) analysis by a high-voltage electrochemical workstation instead of a traditional DC power source. Dewaterability limits of biosolids EDW were identified under a constant-voltage dewatering mode with different applied voltages at 10, 20, 30, 40, and 50 V, independently. The LSV tests reveal that the dewaterability limit of sludge is attributed to the higher electrical resistance of the sludge layer near the anode. The mass of the filtrate flow was linearly proportional to the total amount of electric charge corresponding to the energy consumption in EDW, which elucidated the principal mechanism of EDW. Under a constant-voltage dewatering mode, the applied voltage is a key factor in controlling the energy consumption. Reducing the applied voltage while extending the dewatering time is proposed to reduce the energy consumption and obtain a good dewatering result. As the applied voltage decreased from 50 to 10 V, the energy consumption could be reduced from 403.6 to 80.3 kWh/m 3 removed water, the dewatering times was increased from 6.4 to 85.4 min, and the dry solids content of dewatered cake increased from 16.1 to 34.4 wt%. Those results indicate that LSV is an effective method to reveal the mechanism of EDW and optimize the operation parameters to reduce energy consumption.

It is urgent to develop recycled ionic liquids (ILs) as green solvents for sustainable biomass pretreatment. The goal of this study is to explore the availability and performance of reusing 1-allyl-3-methylimidazolium chloride ([amim]Cl) and 1-butyl-3-methylimidazolium acetate ([bmim]OAc) for pretreatment, structural evolution, and enzymatic hydrolysis of eucalyptus. Cellulose enzymatic digestibility slightly decreased with the increased number of pretreatment recycles. The hydrolysis efficiencies of eucalyptus pretreated via 4th recycled ILs were 54.3% for [amim]Cl and 72.8% for [bmim]OAc, which were 5.0 and 6.7-folds higher than that of untreated eucalyptus. Deteriorations of ILs were observed by the relatively lower sugar conversion and lignin removal from eucalyptus after 4th reuse. No appreciable changes in fundamental framework and thermal stability of [amim]Cl were observed even after successive pretreatments, whereas the anionic structure of [bmim]OAc was destroyed or replaced. This study suggested that the biomass pretreatment with recycled ILs was a potential alternative for low-cost biorefinery.

A π-conjugated microporous poly(benzothiadiazole) (hereafter denoted as BBT) is synthesized through palladium-catalyzed Sonogashira-Hagihara cross-coupling polycondensation, and used as a novel organic semiconductor photocatalyst for both photocatalytic H2 production and pollutant degradation under visible light (λ > 420 nm) irradiation. Furthermore, BBT/TiO2 heterojunction is conveniently fabricated through an in-situ polycondensation procedure of 4,7-dibromobenzo[c][1,2,5]thiadiazole and 1,3,5-triethynylbenzene in the presence of commercial TiO2. After optimizing the composition ratio, the resultant BBT/TiO2 heterojunction exhibited dramatically enhanced visible-light-responsive photocatalytic activities (∼18.0 and 20.4 times higher activity for H2 evolution and ciprofloxacin degradation, respectively) as compared BBT alone. Detailed investigations revealed that the BBT/TiO2 heterojunction interface can accelerate the photogenerated electron transferring from BBT to TiO2, and then improve the photoactivity. The present work exhibits some interesting points and dramatic improvement of photoactivity when an organic semiconductor is combined with an inorganic one, which provides a novel direction to exploit and fabricate photocatalyst for solar energy conversion and pollutant degradation.

Phase-controlled solvothermal synthesis has been proposed for the synthesis of nickel sulfide of single phase including α-NiS, Ni3S4 and NiS2 by tuning the reaction time and the addition of surfactant. The phase evolution of nickel sulfide proceeds with the increase of sulfur stoichiometry with longer reaction time in the presence of surfactant. With the addition of hexadecyl-trimethyl-ammonium bromide (CTAB), a higher sulfur stoichiometry NiS2 phase with hollow sphere geometry was synthesized at 9 h, a much shorter time due to the enrichment of S2− on CTAB micelle surface, followed by the transformation to single phase Ni3S4 finally due to dissipation of enriched sulfur to the bulk solution. The application of these three single phase materials in supercapacitors was investigated. The α-NiS electrode material outperformed the Ni3S4 and NiS2 electrodes, exhibiting a much higher specific capacitance of 800 F g−1 at 0.5 A g−1, attributable to the small particle size, high electrical conductivity and the unique hexagonal crystal structure.

In this study, the long-term stability of Cr(VI) in the FeSO4 and H2SO4 (FeSO4-H2SO4) treated chromite ore processing residue (COPR) after 400 curing days and the stabilization mechanisms were investigated. FeSO4-H2SO4 treatment significantly reduced toxicity characteristic leaching procedure (TCLP) and synthetic precipitation leaching procedure (SPLP) Cr(VI) concentrations to lower than the regulatory limit of 1.5mgL-1 (HJ/T 301-2007, China EPA) even for the samples curing 400days, achieving an outstanding long-term stability. Our independent leaching tests revealed that H+ and SO42- have synergistic effect on promoting the release of Cr(VI), which would make Cr(VI) easier accessed by Fe(II) during stabilization. The contributions of H+ and SO42- to Cr(VI) release ratio were 25%-44% and 19%-38%, respectively, as 5mol H2SO4 per kg COPR was used. X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and alkaline digestion analyses were also employed to interpret the possible stabilization mechanism. Cr(VI) released from COPR solid was reduced to Cr(III) by Fe(II), and then formed stable FexCr(1-x)(OH)3 precipitate. This study provides a facile and reliable scheme for COPR stabilization, and verifies the excellent long-term stability of the FeSO4-H2SO4 treated COPR.

In this study, a novel π-conjugated microporous poly(benzothiadiazole)–graphitic carbon nitride (BBT–C3N4) photocatalyst was synthesized through a facile in situ palladium-catalyzed Sonogashira–Hagihara cross-coupling polycondensation of 4,7-dibromobenzo[c][1,2,5]thiadiazole with 1,3,5-triethynylbenzene in the presence of evenly dispersed g-C3N4 using mixed DMF/TEA as solvent at 80 °C. Systematic characterization results revealed that BBT was equally dispersed on the surface of C3N4 with chemical bonds. The photocatalytic tests showed that this BBT–C3N4 composite exhibited enhanced photocatalytic removal of both sulfathiazole and Cr(VI) in comparison with the pure BBT and C3N4 as well as a mechanical mixture of BBT and C3N4, indicating that the oxidation and reduction abilities of BBT–C3N4 were simultaneously enhanced after composition under visible light irradiation. This was subsequently confirmed by radical detection, PL analysis and scavenger experiments as well. Holes and photoelectrons were demonstrated to be the main active species during the photocatalytic removal of sulfathiazole and Cr(VI), respectively. A possible photoelectron transfer mechanism for efficient photoinduced electron–hole separation of BBT–C3N4 composites is proposed based on all the results. This study provides new insight into the design of highly efficient visible light-driven photocatalysts with superior redox ability for wastewater treatment.

Two types of deep-dewatered sewage sludge cakes were produced from pilot-scale experiments by using two composite conditioners: FeCl3 + quick lime (Fe–Lime) and Fenton's reagent + red mud (Fenton–RM). The feasibility of direct reuse without any solidifying agents of these two deep-dewatered cakes, with water content of about 60 wt%, as landfill cover materials was investigated. Geotechnical properties of these two sludge cakes were found appropriate for reuse as landfill covers. Their plasticity index values increased significantly from 11.6 (raw sludge) to 23.8 (Fe–Lime) and 35.4 (Fenton–RM). The unconfined compressive strength and direct shear strength of the two deep-dewatered sludge cakes could meet or exceed the requirement of landfill cover materials after a certain curing time. Microstructural analyses of scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed that their microstructures were more porous than that of raw sludge since the skeleton builders played a role in building the rigorous framework. There was negligible leaching of Cu, Zn, Pb, Cd and Cr from the deep-dewatered sludge cake from the toxicity characteristic leaching procedure and column leaching test. Both deep-dewatered sludge cakes could be reused as effective landfill cover materials with a suitable curing time.

The interaction between lithium polysulfides and doped heteroatoms could prevent the loss of soluble polysulfides in the cathode and mitigate the shuttle effect in lithium–sulfur batteries. Herein, a facile synthesis of mesoporous graphene platelets (NSGs) with in situ nitrogen and sulfur doping by the pyrolysis of a self-assembled L-cysteine precursor on sodium chloride crystal surface for structure-directing is presented. The mesoporous lamellar structure of the NSG possesses a uniform distribution of pyrrolic N, pyridinic N, and thiosulphate structured heteroatoms originating from in situ doping, which promotes the confinement of intermediate polysulfides. Combining the strong interactions with soluble polysulfide, flexible mesoporous architecture, and high conductivity of graphene, the prepared NSG material exhibited a high initial capacity of 1433 mA h g−1 at a 2C rate as well as a reversible capacity of 684 mA h g−1 after 200 cycles. This demonstrates that the in situ nitrogen and sulfur doped thin lamellar structure of graphene would be a promising cathode material for high performance lithium–sulfur batteries.

A delaminated MXene-bismuth (Bi@d-Ti3C2) nanocomposite was synthesized for the construction of a microgrid electrochemical sensor via mechanical milling. The Bi@d-Ti3C2 nanocomposite was synthesized by accumulation of Bi(III) on the surface of delaminated Ti3C2 nanosheets through electrostatic attraction and subsequent in-situ growth of bismuth nanorods. Under optimized experimental conditions, the sensor exhibits (a) linear responses to Pb(II), Cd(II) and Zn(II) in the concentration range from 1 to 20 μg L−1, (b) well separated peak potentials at −0.54 V, −0.76 V and − 1.15 V vs. Ag/AgCl, (c) sensitivities of 0.98, 0.84 and 0.60 μA L μg−1, and (d) detection limits of 0.2, 0.4 and 0.5 μg L−1, respectively. This performance is attributed to the uniform dispersion of Bi nanorods on electrically conductive delaminated Ti3C2 MXene, and to the enhanced diffusion due to the microgrid structure.

During advanced oxidation treatment for enhancing sludge dewaterability, the peptide chains of protein can be decomposed into amino acids. Protein exhibits a great impact on sewage sludge dewaterability. However, the role of amino acids in sludge dewatering remains unclear. In this study, among the 23 types of amino acids investigated, tryptophane (Trp) and lysine (Lys) were identified as the key amino acids affecting sludge dewaterability during Fenton oxidation treatment. The content of lysine showed positive correlations with capillary suction time (CST), specific resistance to filtration (SRF), and bound water content, and the concentrations of total protein, low molecular weight protein, amines and amides, and 3-turn helix of proteinaceous compounds in bound extracellular polymeric substances (EPS), while the content of tryptophane showed negative correlations with the above parameters. The amino acids may be sourced from damage of the membrane and ribosomal proteins by hydroxyl radicals, and the peptide bonds connected with tryptophane were more inclined to be decomposed than other amino acids. Particularly, more amino acids of tryptophane can result in more hydrophobic interaction, and less necessary energy barrier for aggregation of particles. As such, regulating protein degradation towards production of tryptophane may be related with enhanced sludge dewaterability by Fenton oxidation treatment.

The novel catalyst LaCu

Most previous studies of phosphorus (P) removal focused on investigation of the soluble, and particulate P, but ignoring the difference between organic and inorganic P. In this study, the effects of various flocculants, namely polyacrylamide (PAM) and polyaluminum chloride (PAC), on flocculation efficiency in different P speciations (organic and inorganic P) were investigated. A modified method to differentiate between organic and inorganic P content in secondary effluent samples was developed. The results showed that P speciation based on organic/inorganic P (Pearson’s correlation R = 0.915, p 0.05) in evaluating the P content in secondary effluents. The liquid 31P nuclear magnetic resonance measurements results indicated that PAM was more effective in removing organic P (phosphonates and orthophosphate monoesters) rather than inorganic P. However, PAC was more effective in removing inorganic P (particularly orthophosphate) rather than organic P. Based on the modeled results of a response surface methodology (RSM), doses of PAM and PAC were optimized for secondary effluent containing different amounts of organic and inorganic P from the two typical wastewater treatment plants (WWTPs) in Wuhan city, China.

Biogas and phosphorus recovery from waste activated sludge (WAS) with sequential homogeneous protocatechuic acid (PCA) enhanced Fenton pretreatment, anaerobic digestion (AD) and microbial electrolysis cell (MEC) were investigated. The cumulation of biogas production of WAS-Fenton-AD was 330.4 mL/g VS, which was 2.05-fold of the control without pretreatment (WAS-AD) during anaerobic digestion. Biogas production of 178 mL/L/d from WAS-Fenton-AD-MEC was achieved, which was 5.23-fold of the WAS-MEC, 2.28-fold of WAS-Fenton-MEC and 1.46-fold of WAS-AD-MEC, respectively. Enhanced phosphorus recovery in form of struvite reached 1.72 g/g TS (18.03% of total P) with a purity of 74.4%. Microbial community richness and diversity analysis revealed that the pretreatment process under circumneutral condition improved the diversity of microbial community, which was consisted of Bacteroidetes (33.90%), Proteobacteria (33.14%), and Chloroflexi (10.14%), compared to a majority of Firmicutes (70.81%) in WAS-AD. This study provides a feasible strategy for the recovery of biogas combined with phosphorus from WAS.

Arsenic-alkali residue (AAR) from antimony smelting is highly hazardous due to its ready leachability of As, seeking for proper disposal such as stabilization treatment. However, As stabilization in AAR would be challenging due to the high content of coexisting soluble carbonate. This study conducted the stabilization treatments of AAR by ferrous sulfate and lime, respectively, and revealed the significant influence of coexisting carbonate. It was found that ferrous sulfate was more efficient than lime, which required only one-tenth of dosages of lime to reduce the As leaching concentration from 915 mg/L to a level below 2.5 mg/L to meet the Chinese regulatory limit. The combining qualitative and quantitative analyses based on XRD, SEM–EDS, and thermodynamic modeling suggested that the formation of insoluble arsenate minerals, ferrous arsenate or calcium arsenate, was the predominant mechanism for As stabilization in the two treatment systems, and their efficiency difference was primarily attributed to the coexisting carbonate, which had a slight effect on ferrous arsenate but severely obstructed calcium arsenate formation. Moreover, the examination of As leaching concentrations in 1-year-cured samples indicated that the long-term stability of ferrous sulfate treatment was far superior to that of lime treatment. This study provides ferrous salts as a promising and green scheme for stabilization treatment of AAR as well as other similar As-bearing solid wastes with coexisting soluble carbonate. Keywords: Arsenic-alkali residue, Arsenic stabilization, Ferrous sulfate, Lime, Arsenate minerals, Coexisting soluble carbonate

The recovery of copper (Cu0) from waste printed circuit boards (WPCBs) is a great challenge as a result of its heterogeneous structural properties, with a mixture of metals, epoxy resin, and fiberglass. In this study, a three-step sequential process, including mechanochemical processing, water leaching, and recrystallization, for Cu0 recovery from WPCB powder is reported. Potassium persulfate (K2S2O8), instead of acid/alkali reagents, was employed as the sole reagent in the cupric sulfate (CuSO4) regeneration process. Complete oxidation of Cu0 in the WPCBs to copper oxide (CuO) and CuSO4 was first achieved during mechanochemical processing with K2S2O8 as the solid oxidant, and the K2S2O8 was simultaneously converted to sulfate compounds [K3H(SO4)2] via a solid-solid reaction with epoxy resin (C nH mO y) as the hydrogen donator under mechanical force. The rapid leaching of Cu species in the forms of CuO and CuSO4 was therefore easily realized with pure water as a nontoxic leaching reagent. The kinetics of the leaching process of Cu species was confirmed to follow the shrinking nucleus model controlled by solid-film diffusion. Finally, CuSO4·5H2O was successfully separated by cooling crystallization of the hot saturated solution of sulfate salt [K2Cu(SO4)2·6H2O]. An efficient conversion of Cu0 to CuSO4·5H2O product, for WPCB recycling, was therefore established.

A microbial fuel cell system with intimately coupled photocatalytic-electrogenic anode (photocatalytic-MFC) was proposed for the synergetic degradation of 2,4,6-trichlorophenol (2,4,6-TCP) which has a structure of three chlorine groups connecting to a phenol ring and is well recognized as a recalcitrant pollutant for its high toxicity, bioaccumulation and persistence. The photocatalytic-electrogenic anode was prepared by coating mpg-C3N4 on a carbon felt anode, followed by inoculating with municipal sewage and acclimating with 2,4,6-TCP at gradient concentrations. Improved TCP degradation was achieved, showing 79.3% of TCP removal in 10 h with an original concentration of 200 mg L−1, which was higher than that obtained with the unilluminated MFC (66.0%) and the photocatalytic-only process (56.1%). The coupled photocatalytic-electrogenic process demonstrated different degradation pathways compared with the photocatalytic-only process, with one open-chain compound (2-chloro-4-keto-2-hexenedioic acid, 2-CMA) detected in the photocatalytic-MFC system. Microbial community analysis revealed that Pseudomonas, instead of Geobacter observed in the unilluminated MFC bioanode, dominated in the photocatalytic-electrogenic anode MFC biofilm, which might be responsible for enhanced current generation in the coupled system. In addition, biofilm rich with Rhodococcus on air-cathode was also responsible for the enhanced TCP removal. This research provides an efficient strategy for the treatment of wastewater with recalcitrant contaminants by intimate-coupling of the photocatalytic and the electrogenic processes.

A liquid–gas two-phase computational fluid dynamics (CFD) model was developed to simulate flow field and gas hold-up in a pilot-scale oxidation ditch (OD). The volume of fluid (VOF) model and the mass flow inlet boundary condition for gas injection were introduced in this model. The simulated values of the flow velocities and the gas hold-up were verified by experimental measurements in the pilot-scale OD. The results showed that the gas hold-up at test-site 3, immediately downstream of the surface aerator, was the highest among all three test-sites. Most of the gas existed in the upper portion of the ditch and was close to the inner side of the channel. Based on the liquid–gas two-phase CFD model, three operating conditions with different setting height ratios of the submerged impellers were simulated. The simulated results suggested that the setting heights of the submerged impellers have significant impacts on the flow velocity distribution. Lowering the setting height could increase the flow velocity in the pilot-scale OD. An optimal setting height ratio of 0.273 was proposed, which would be beneficial for minimizing sludge sedimentation, especially near the inner side of the curve bend.

The facile synthesis of sulfur scaffold with high electrical conductivity and strong polysulfide immobilization capability plays an important role in developing high-performance lithium sulfur batteries. Here a new type of porous N-doped carbon fiber consisting of hollow carbon nanoparticles (9 wt%-CF) is designed as sulfur scaffold through electrospinning and carbonization processes with ZIF-8 and polyacrylonitrile as precursors. The carbon fiber skeleton can provide high electrical conductivity, and interconnected hollow particles provide ample space to host active materials and to immobilize polysulfides. Moreover, the N-doping further improves the interaction between 9 wt%-CF and polysulfides. Consequently, the as-prepared 9 wt%-CF/S cathode delivers an initial discharge capacity of 1524 mAh g−1 at 0.1 C and high capacity retention of 83% after 200 cycles charge/discharge at 0.5 C with a sulfur loading of 1.9 mg cm−2.

In this study, water-permeable bricks were prepared from fly ash (FA) by autoclaving. Granulated FA prepared by geopolymerization was used as aggregate and mixed with fine FA to achieve a high content of FA (>50 wt%) in water-permeable bricks. Effects of sodium silicate dose, water/fine FA mass ratio, forming pressure and autoclaving time on the performance of water-permeable bricks were investigated. Under optimal conditions, the compressive strength and permeability coefficient of prepared bricks could reach 35.5 MPa, and 1.044 × 10-4 m/s, respectively. The mineral compositions, micro-morphology, and pore distribution of the permeable bricks were investigated. The pore structure of permeable bricks was investigated by using mercury intrusion porosimetry and micro computed tomography. The connected pores in bricks contribute to the higher water permeability coefficient.

The debromination of brominated epoxy resins (BERs) from waste printed circuit boards (WPCBs) is of great challenge due to its high structural stability. An enhanced subcritical water (SCW) process with alkaline additive is proposed for efficient debromination of BERs, and the mechanism of alkaline additive on bromine removal has been investigated. More than 95.11% of bromine is removed under the optimal conditions. Both enhanced fiberglass destruction and BERs degradation contribute to the efficient debromination process. Structure of Ca−Al, Si−O, and Al−O bonds in fiberglass is destroyed by alkaline corrosion, releasing BERs into the solution and facilitating the debromination process. Meanwhile, phenol, 2-bromophenol and catechol are the main products of BERs degradation. Nucleophilic substitution reaction by the bimolecular process dominantly contribute to the debromination. The energy barrier of the bimolecular process is only 15.9 kcal/mol, which is much lower than that of the direct dissociation energy of C−Br bond (168.3 kcal/mol). Ion association of KOH is weaker than that of NaOH in the alkaline-enhanced SCW process due to the difference of cation radius, proved by ab initio molecular dynamics simulation. An efficient approach for WPCBs debromination under mild conditions has been proposed.

A hybrid electrochemical process with Ca(ClO)2 addition for simultaneous sludge dewaterability, stabilization and phosphorus fixation was proposed. Under optimal conditions (150 mg/g VS Ca(ClO)2, 15 V), the capillary suction time (CST) and specific resistance to filtration (SRF) were decreased by 88% and 92%, respectively. Efficient sludge stabilization with E. coli colonies of less than 1000 MPN/g TS was achieved. Phosphorus of 99% was removed from the filtrate and successfully fixed in the sludge cake and on the electrode surface. The integration of electrochemical and hypochlorite oxidation could effectively degrade the tightly bound extracellular polymeric substances (TB-EPS) structure with a total organic carbon (TOC) reduction of 52%. Besides, the disintegration of microbial cell envelopes was also achieved, with a reduction of living cell fraction of 98%. Furthermore, system pH could be maintained at near neutral (7.45) and the conversion of Fe(II) to Fe(III) was also facilitated with the addition of Ca(ClO)2, resulting in improved electrocoagulation process for enhanced sludge dewatering and phosphorus fixation. The multifunctional effects were achieved with the cooperated extracellular electrooxidation for EPS destruction and the active chlorine for intracellular microbial cell disintegration. This research provides a promising strategy for integrated sludge treatment and recycling for possible land utilization.

Although polyhalogenated carbazoles (PHCZs) can be generated and detected in drinking water, their occurrence and potential health risks to humans via drinking water ingestion are not well known. In this study, 11 PHCZs were screened in drinking water samples from Wuhan, the most populous city in central China. The total concentration of PHCZs could be up to 53.48 ng/L with a median level of 8.19 ng/L, which was comparable to polychlorinated biphenyls and poly- and perfluoroalkyl substances reported in the literatures for drinking water. Composition profiles revealed that 3,6-dichlorocarbazole, 3-chlorocarbazole, 3-bromocarbazole and 3,6-dibromocarbazole were the predominant PHCZ congeners in the tested samples. Regional differences in the levels and patterns of PHCZs suggested that anthropogenic releases should be the dominant source compared to natural generation. Boiling of the water samples caused no significant change in PHCZs concentrations after correcting the volume change due to evaporation. Potential health risks associated to the levels of PHCZs in drinking water were assessed using the toxic equivalent (TEQs) method. The estimated daily intake of PHCZs via drinking water ingestion is up to 0.38 pg-TEQ/kg body weight/day for infants, nearly 4.5 times higher than that for adults, and appears to reach the maximum permissible concentration set by certain authority agencies. Overall, drinking water ingestion represents an important exposure pathway for PHCZs. This is the first comprehensive study on the abundance and health risks of PHCZs in drinking water.

The dramatic increase in global generation of e-wastes has become a great challenge for sustainable development, and strategies for efficient and environmental-friendly recycling and disposal of e-waste are of great demand. A cost-effective strategy of crushing pretreatment combined with pyrolysis to recover metals from waste printed circuit boards (WPCBs) has been developed. Effects of particle size and pyrolysis temperature on metal recovery were explored. The optimal combination of less energy consumption and higher metal recovery was obtained when the pretreated particle size was 4.0 cm and pyrolysis temperature was 330 °C. The Cu and Sn were recovered as zero-valent copper and tin-copper alloy with the recovery efficiency of 92.38 and 99.80 wt%, respectively. Brominated pollutants are easily controlled when pretreated particle size is larger than 2.0 cm and pyrolysis temperature is below 400 °C. Under the optimal crushing pretreatment and pyrolysis conditions, the bromine contents in the pyrolysis products of solid residues, liquid tar, and gas were 45.45 wt%, 38.70 wt%, and 15.85 wt%, respectively. The structure of WPCBs was destroyed at 275–525 °C due to decomposition of brominated epoxy resins (BERs), which could be accurately characterized by 8 dominating reactions through pyrolysis kinetics analysis. The main reactions took place at conversion of 0.14 and 0.15, corresponding to a pyrolysis temperature of 306–342 °C. Thus, the interlayer bonding force of WPCBs significantly decreased, contributing to effective separation of metals in WPCBs.

Modification of exoelectrogens with conjugated polymers is an efficient strategy to improve extracellular electron transfer (EET) from individual cells to electrode. However, due to the hydrophobic nature of conductive polymers, improving cell-electrode adhesion needs to be addressed. In this research, we report the modification of Shewanella oneidensis MR-1 by successively in situ coating individual cells with polypyrrole (PPy) and adhesive polydopamine (PDA). The PPy-PDA modified cells display improved conductivity and adhesion. We employ PPy-PDA modified cells as anode in microbial fuel cells (MFCs) and find that electro-activity of anode is greatly improved as direct EET is improved, and riboflavin secretion which is conducive to indirect EET is enhanced. The maximum power density of MFCs employing PPy-PDA modified cells is 11.8 and 4.8 higher than that of PPy modified and unmodified cells, respectively. Our results indicate this in situ modification of exoelectrogens with PPY-PDA offers a facile and promising strategy for performance improvement of MFCs.

A novel method to enhance sludge dewaterability with ammonium sulfate ((NH4)2SO4) was proposed, and the potential reuse of dewatered sludge cake and filtrate as nitrogen fertilizers was evaluated. Compared with raw sludge, 87.91% reduction of capillary suction time (CST) and 88.02% reduction of specific resistance to filtration (SRF) after adding 80% (m/m) (NH4)2SO4 were achieved, with 38.49% of protein precipitated simultaneously. The (NH4)2SO4 dose destroyed cell membrane, resulting in the release of intracellular water by converting bound water into free water, thus enhancing sludge dewaterability. In the solid phase, the content of protein-N increased, and larger protein aggregates were formed. The (NH4)2SO4 dose destroyed the hydration shell, making proteins to exhibit hydrophobic interactions, and to be aggregated, and precipitated from the liquid phase. When incubated Pennisetum alopecuroides L. with the dewatered sludge cake and filtrate after dewatering and conditioning with (NH4)2SO4, the germination rate of grass seed and shoot lengths both increased while compared with those incubated with dewatered sludge cake and filtrate of the raw sludge. This study might provide insights into sustainable sludge treatment by integrating sludge dewatering and the potential reuse of dewatered sludge cake and filtrate as nitrogen fertilizer via treatment with (NH4)2SO4.

This study investigated the pyrolytic performances of deep-dewatered sludge cakes which were previously conditioned with Fenton's reagent and red mud. The pyrolytic products, including fuel gas, tar and solid char, were characterized by GC, GC-MS and FTIR. The results showed that pyrolysis of sludge cakes conditioned with Fenton's reagent and red mud produced more gas, especially higher H2 yield, compared with pyrolysis of raw sludge. In addition, red mud promoted PAHs formation and tar re-formation through side-chain-cleaving, dehydrogenation, polycondensation and aromatization of hydrocarbon during the pyrolysis, resulting in enhancement of the H2 yield. The sharp decrease in the absorbance of C Haromatic group of chars from the conditioned cakes implied that red mud could intensify the cracking and re-formation of aromatics. The higher the iron oxide content in red mud was, the better catalytic efficiency in the decomposition of organics and tar re-formation was, which led to more H2 production.

Sludge samples taken from different sources and times may have different characteristics that could affect dewatering performance. In this study, 20 sludge samples from five wastewater treatment plants and different seasons in 1 year were characterized. Pearson correlation analysis indicated that solid content (SC), total suspended solid (TSS), polysaccharides and proteins contents had positive correlations with the capillary suction time (CST), whereas volatile suspended–solid/total suspended solid (VSS/TSS) exhibited negative correlations with CST. Moreover, no correlations between CST and specific resistance to filtration were found among these different sludge samples. The principal component analysis confirmed that only two group variables could represent most of the sludge characteristic parameters. The first set of variables represents the particulate nature of the biotic factors (SC, VSS/TSS, SCOD, TSS, polysaccharides and proteins), and the second set is the pH. CST could not be a reasonable indicator of dewaterability in sludge deep dewatering by Fe2+/S2O8 2−-phosphogypsum composite conditioning. Furthermore, the results of diaphragm filter press dewatering showed that initial SC and VSS/TSS were the most dominant sludge characteristics affecting the solid content of dewatered cake (R p = 0.610, p = 0.016; R p = −0.838, p = 0.000, respectively) with Fe2+/S2O8 2−-phosphogypsum composite conditioning. Results from this study suggest that dewatering performance is predictable by sludge characteristics parameters for Fe2+/S2O8 2−-phosphogypsum conditioning.

Electrodeposition and electrodissolution reactions of the Pb2+/Pb electrode were studied on a glassy carbon rotating disk electrode in aqueous solutions of CH3SO3H and Pb(CH3SO3)2. The electrolytic parameters, kinematic viscosity and ionic conductivity, were determined with various concentrations of CH3SO3H and Pb(CH3SO3)2. The diffusion coefficient of Pb2+ in this electrolyte prepared with CH3SO3H was determined by the Levich Equation. Both the concentrations of CH3SO3H and Pb(CH3SO3)2 were found responsible for the equilibrium potential shifts and exchange current density variations. The electrochemical processes at the Pb2+/Pb electrode were identified as being under mixed ohmic-diffusion control. The electrolyte conductivity and the ionic activity of Pb2+ were recognized as important parameters for designing the soluble lead redox flow cells. During constant current charge–discharge measurement, the specific capacity of the Pb2+/Pb electrode was about 253 mAh g−1Pb, about 98 % of the theoretical value. The impurity elements Fe, Ba, Al, and Zn in the Pb2+ electrolytes prepared with recycled lead exhibited insignificant influences on the Pb2+/Pb reactions. It is reasonable to believe that the recycled lead can be applied in soluble lead redox flow batteries, and the cost may be further reduced with recycled lead because expensive impurity-control processes seemed to be avoidable.

A novel nano-scale ferrite (MgFe 2 O 4 ) was employed for hexachlorobenzene (HCB) removal in soil with microwave (MW) treatment. MW-generated hole (h + )/electron pair could activate water and oxygen adsorbed on the surface of MgFe 2 O 4 to produce OH and O 2 − . Radical scavenging tests confirmed it was OH but not h + and O 2 − that directly oxidized HCB. O 2 − was a responsible oxidant of intermediates decomposition. Thus the co-existing of water and molecular oxygen had significant enhancement on HCB catalytic oxidation, showing high degradation (80%) and dechloriantion (93%) after 20 min of MW radiation. Electron spin resonance analysis demonstrated that O 2 − and OH radicals were aroused from MW-induced h + /electron activation of molecule oxygen and water, but not from the lattice oxygen and –OH groups in the structure of ferrites. Thermal desorption of HCB occurred at the wide temperature of the surface soil at the range of 90–500 °C, and obviously catalytic oxidation happed at a temperature range of 90–620 °C in the water/oxygen-contained system. Complicated pyrolytic reactions happed at 90–670 °C in the absence of water and oxygen. The addition of MgFe 2 O 4 with MW radiation elevated soil temperature, leading to HCB pyrolysis that fitted well with the first order kinetics model. When soil was vitrified at >670 °C, with the process of thermal fixation, changes of the soil structure took place.

Barium sulfate (BaSO4) is a common impurity in recycled lead paste that is challenging to eliminate completely during hydrometallurgical recycling of spent lead acid batteries, so the effect of this impurity in positive active materials on the performance of recycled lead acid batteries was investigated. The BaSO4 doped lead oxide composite was used as a positive active material in positive plates of lead acid batteries with theoretical capacities of 2.0 A h. BaSO4 was retained in the solid phase throughout the battery fabrication process. Different BaSO4 dosages affected the phase of the positive plates during the curing process, with the highest content of metallic lead obtained at a BaSO4 dosage of 0.06 wt%. Morphology analysis indicated that aggregates were formed in the positive plates and the particles became rougher with increasing addition of BaSO4 during the formation process. BaSO4 also demonstrated a large impact on charge/discharge cycles with 100% DOD in battery testing. Analysis of disassembled failed batteries indicated that the expansion and shedding-off of the positive active material were mainly responsible for the failure of these batteries, and this could be attributed to the non-uniform growth of lead oxide on the BaSO4 nucleus, and the accumulation of internal stress.

A novel ultrasensitive, selective and low cost electrochemical sensor based on a hollow sphere bismuth oxide doped mesoporous carbon aerogel nanocomposite derived from a sustainable biomass material was successfully fabricated for simultaneous Pb2+ and Cd2+ detection at picomolar levels. In this nanocomposite material, we successfully brought together the advantages of an extraordinarily large surface area biomass derived carbon matrix with mesopores for analyte pre-enrichment and the excellent electroanalytical activity of the bismuth oxide hollow sphere structure for highly sensitive heavy metal sensing. Under optimized conditions, this electrode material exhibited a very low detection limit of 1.72 pM for Pb2+ and 1.58 pM for Cd2+ under ambient conditions, the lowest ever limit of detection recorded for the detection of both Pb2+ and Cd2+ using activated carbon. Furthermore, two wide linear ranges from 0.5 pM to 10 pM and from 10 pM to100 pM were observed due to the differences of adsorption dynamics at different metal ion concentration ranges. The nanocomposite sensor material demonstrated excellent reproducibility and great resistance to interference. Furthermore, the application for real water analysis was demonstrated and the result was highly consistent with the measurement from inductively coupled plasma optical emission spectroscopy (ICP-OES).

A conjugated oligoelectrolyte (COE), which spontaneously aligns within cell membranes, was shown to completely inhibit H2 uptake by Geobacter sulfurreducens in microbial electrolysis cells. Coulombic efficiencies that were 490±95%, due to H2 recycling between the cathode and microorganisms on the anode, were reduced to 86±2% with COE addition. The use of the COE resulted in a 67-fold increase in H2 gas recovery, and a 4.4-fold increase in acetate removal. Current generation, H2 recovery and COD removals by Geobacter metallireducens, which cannot use H2, were unaffected by COE addition. These results show that this COE is an effective H2 uptake inhibitor, and that it can enable improved and sustained H2 gas recovery in this bioelectrochemical system.

Geopolymers have been introduced as a promising strategy for the solidification/stabilization (s/s) of heavy metals due to its sustainability and environmental friendliness. However, it usually takes a long curing time to achieve a rational mechanical strength, and the stability of heavy metals in geopolymer needs to be further enhanced to reduce possible environmental risks. Here we introduced a microwave (MW) strategy for the s/s of real lead slag with geopolymer technology. The stabilization of lead slag (LS) with different addition ratios were characterized, and the effect of microwave power as well as irradiation time were also examined to optimize the geopolymer strength and the leaching of Pb. The geopolymerization process was drastically enhanced, showing shortened polymerization period from 28 days to 15 min with an optimum compressive strength of 18.8 MPa and s/s efficiency of 98.73%. It was revealed that physical embedding was the main stabilization mechanism proved by lead speciation, X-Ray Diffraction (XRD), Fourier Transform Infrared Spectrometry (FTIR), Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometry (EDS) analysis. It suggested that the combined effects of local heating and enhanced dehydration with MW irradiation would benefit the stabilization of lead slag in geopolymers.

Reuse of sludge-derived Fe-rich biochar as sludge conditioner is an attractive route for management of waste activated sludge at source. Homogeneous and heterogeneous Fenton reactions have been proved in sludge conditioning with Fe-rich biochar activating H2O2 to enhance sludge dewaterability. The FeAl2O4 phase in Fe-rich biochar was first identified during pyrolysis of sewage sludge after adding both Fe2O3 and Al2O3, since Fe and Al elements are two of major metal elements in Fe-rich sludge. Compared with the Fe-rich biochar that did not comprise FeAl2O4 phase, the capillary suction time (CST) and specific resistance to filterability (SRF) of the sludge conditioned with the Fe-rich biochar comprising FeAl2O4 phase could be efficiently decreased by 23% and 44%, respectively. The results indicated that FeAl2O4 phase in Fe-rich biochar could improve sludge dewaterability by enhancing heterogeneous Fenton reaction. Synergistic effect between Fe and Al in FeAl2O4 contributed to weak the O-O bond in H2O2 and reduce the activation energy of H2O2 decomposition for enhancing ·OH generation, which could be explained by density functional theory (DFT) calculations for the first time. Thus, the decomposition rate of H2O2 and the amount of ·OH generation were obviously promoted by FeAl2O4 phase in sludge-derived biochar during sludge conditioning, attributing to the destruction of sludge flocs, the release of bound water, and the improvement of sludge dewaterability.