•The effect of calcination conditions on catalytic cracking of toluene over 3Fe8Ni/PG were comprehensively studied.•3Fe8Ni/PG reduced at 700 °C for 2 h had the best catalytic performance.•Steam reforming of toluene over 3Fe8Ni/PG catalyst was evaluated.•The deactivation mechanism of 3Fe8Ni/PG catalyst was discussed.In this paper, the effect of calcination conditions on catalytic cracking of toluene over 3Fe8Ni/PG (PG: palygorskite) was investigated. The experimental parameters including the calcination temperature, time and atmosphere and reaction temperature were evaluated. The catalysts were characterized using X-ray diffraction (XRD), H2 temperature-programmed reduction (TPR), transmission electron microcopy (TEM) and Raman spectroscopy. The gas composition was analyzed by a gas chromatograph (GC). The results showed that 3Fe8Ni/PG catalyst exhibited a higher catalytic reactivity for catalytic cracking of toluene than that of thermal cracking over quartz. In consideration of the thermal stability and catalytic reactivity of catalyst, a proper calcination temperature and time should be employed in the preparation of 3Fe8Ni/PG catalyst. The 3Fe8Ni/PG reduced in hydrogen at 700 °C for 2 h showed the highest catalytic reactivity as evidenced by the toluene conversion of 100% at the reaction temperature of 550 °C. The catalytic reactivity of 3Fe8Ni/PG reduced in hydrogen for toluene conversion was superior to that of 3Fe8Ni/PG calcinated in air, 3Fe/PG, and 8Ni/PG, which revealed that the awaruite (NiFe) was the active component for the decomposition of toluene. Moreover, steam reforming of toluene over 3Fe8Ni/PG catalysts suggested that 80% toluene conversion can be achieved and most of toluene was converted into H2 and CO. Both amorphous carbon and graphitic carbon species were formed on 3Fe8Ni/PG catalysts after the catalytic reaction. The D/G ratio (the relative intensity of D-band to G-band ratio) was positively correlated to the catalytic reactivity of 3Fe8Ni/PG catalysts.

•OH + ONO2* was predominant channel of HO2NO2 photolysis in aqueous phase at 266 nm.•The quantum yield of OH radicals of HO2NO2 photolysis was to be 0.14 ± 0.01.•OH react with HO2NO2 with a rate constant of (1.58 ± 0.03) × 109 L mol−1 s−1.The photodissociation of peroxynitric acid (HO2NO2) aqueous solution both in nitrogen-saturated and oxygen-saturated were studied by using 266 nm laser flash photolysis techniques. Hydroxyl radical and NO3 radical was observed in the time resolved spectra from the photolysis of HO2NO2. The yield of NO3 at 266 nm of 0.12 ± 0.02 was consistent with OH quantum yield of (0.14 ± 0.01) A small OH yield indicated that OH was mainly from the direct photodissociation of peroxynitric acid and OH + NO3 was predominant photolysis channel (if not the only photolysis pathway) from the HO2NO2 photolysis in the aqueous phase. The pKa of HO2NO2 was calculated to be 5.93. OH radical would sequentially react with HO2NO2 to form OHHO2NO2 adduct with a second-order rate constant of (1.58 ± 0.03) × 109 L mol−1 s−1.Download high-res image (99KB)Download full-size image

•A novel parameter (R) was defined to evaluate the goethite influence on methanogenesis.•R represented the ratio of available surface site of iron oxide to the acetate in reactor.•Goethite facilitates methanogenesis at −3 to 0 and suppressed it at 1.7–3 of R values.•R can also be used to evaluate and predict the influence of other iron oxides on methanogenesis.The influence of iron oxide on anaerobic methanogenesis has been researched for several decades. Both promotion and inhibition effects have been reported under various conditions. In the current study, the effect of goethite on the methanogenesis of acetate was investigated in batch experiment for a period of 105 days. With the increasing dosages of goethite from 0.45 to 90 mM, the methane yield increased from 0.72 to 0.91 mM-CH4 mM-Ace−1, which was significantly higher than the methane yield of the control without goethite supplementation as 0.56–0.64 mM-CH4 mM-Ace−1, indicating that the added goethite had facilitated methanogenesis. The solid in culture was analyzed by electron microscopy. The tight binding of goethite and microbial cells indicated that the promotion of methanogenesis might be caused by the enhancement of syntrophic effect of methanogenic microorganisms through the electron transfer mediated by the (semi)conduct iron oxide goethite. Based on the analysis of the data from various reports, a novel parameter of iron influence factor (R) was proposed, which represented the ratio of available surface site of iron oxide to the concentration of acetate in reactor, and showed that the methanogenesis was facilitated at goethite lgR values of −3 to 0 and suppressed at goethite lgR values of 1.7–3. This study provided novel insights for the evaluation of iron oxides influence on methanogenesis in anaerobic digestion.

•Siderite annealed for a short time can obtain materials with a high surface area.•The activated siderite has a best performance on removal of phosphate.•A good adsorption property especially in deeply removing phosphate.•Short time storage does not affect the removal capacity.•The activated siderite is an environmental friendly nano-scale material.Activated siderite ore (ASO) was prepared by annealing siderite ore at different temperatures for different durations. The performance of ASO on the removal of phosphate from aqueous solution and the effects of particle size, contact time, pH, initial phosphate concentration, temperature, and coexisting anions on phosphate removal were investigated. X-ray diffractometer, thermogravimetric analyzer (TGA), transmission electron microscopy (TEM), surface area analyzer, Fourier transformed infrared spectra and other techniques were utilized to characterize ASO before and after adsorption. The results showed that a large amount of CO2 was released meanwhile the siderite began to transform to hematite when the annealing temperature increased to 450 °C. The specific surface area of annealed product increased from 4.17 m2/g to 57.5 m2/g as the temperature came to 470 °C. Phosphate can be removed efficiently by ASO in a relatively wide pH range between 3.0 and 11.0. The effects of coexisting anions were not significant within the experimental concentration ranges except HCO3−. The adsorption process of phosphate on ASO fitted pseudo-second order kinetics model. ASO showed a high-efficient adsorption capacity of 9.24 mg/g estimated from Langmuir isotherm at 30 °C. Results of TEM and FTIR analysis suggested that under the condition of pH = 6.5 and phosphate concentration (100 mg/L), two different monoprotonated phosphate complexes exist at ASO, with one surface complex coordinated in a monodentate binuclear (bridging) fashion, and the other as a monodentate mononuclear complex. A small amount of co-precipitation is most likely to be another mechanism for the removal of phosphate. These fundamental data indicate that siderite is a promising precursor for preparing porous material at least for adsorption of phosphate.Download high-res image (382KB)Download full-size image

Elemental sulfur is the most commonly found form of sulfur in anaerobic sediments. Accurate determination of elemental sulfur is the key step to know physical chemistry and biogeochemical processes in the sediments. A novel method was developed for the analysis of elemental sulfur using high-performance liquid chromatography (HPLC) with a C18 column. The procedure of determination of elemental sulfur concentrations from 0.1 to 100 mg/g (on a basis of the dry weight of sediment) is based on the direct injection of acetone extracts of sediments into a chromatographic column. The linearity range of 20–110 mg/L showed an excellent linearity of response (r = 0.999). The limit of detection and limit of quantitation for elemental sulfur were 9.41 and 4.18 μg/L, and converted sulfur mass per sediment mass was 1.88 × 10−2 and 8.36 × 10−3 μg/kg. Besides, a repetitive experiment (ten times) was carried out and the average chromatographic peak area was 141.47 mg L−1. The sulfur concentration in the solution used for the determination of standard deviation and relative standard deviation was 1.02 and 0.727%, respectively. The average recovery ranges between 98 and 100%. The quantitation of elemental sulfur in sediment samples from anaerobic digestion reactor is obvious, and the average concentration of elemental sulfur on the basis of the dry weight of the sediment is 5.24 mg/g. The method was sensitive and exhibited good signal-to-noise ratio, as well as linear responses over a wide concentration range.

•Thermally treated clayey dolomite was carbonized.•Nanoparticles calcite and periclase was obtained by carbonation.•The carbonized products exhibited low thermal stability.•The carbonized products exhibited good performance to Cd (II).•The carbonized products greatly decreased the effluent pH.Highly active porous materials composed of calcite and periclase nanoparticles was prepared by the carbonation of thermally treated clayey dolomite, having great potential for heavy metal pollution control in water and soil. The effect of coexisting steam and hydration pretreatment on the carbonation of calcined clayey dolomite (CCD) was studied by fixed bed reactor and mass spectrum on-line monitoring. The phase, surface chemistry, thermal activity, pore type and morphology of CCD after carbonation were characterized by XRD, FTIR, TG, N2 adsorption–desorption isotherm and TEM. The results showed that the initial and complete carbonation temperatures of CCD under anhydrous conditions were 400 °C and 600 °C, respectively. The presence of 10% steam decreased the initial and complete temperatures by 100 °C, respectively. The complete carbonation temperature was reduced to 400 °C when the CCD was hydrated and dried before carbonation. However, the hydrated CCD which not dried can be directly carbonated at room temperature, and the carbonation rate (newborn calcite mass fraction) firstly decreased, then increased with the increase of temperature in the range of 50–500 °C. According to the TG results, the decomposition temperatures of the newborn calcite produced by 650 °C carbonation of CCD decreased by 50 °C compared with that of common calcite. The research on cadmium removal showed that the removal efficiency of 50 mg/L Cd (II) by 650 °C carbonation of CCD rapidly reached 99.8% within 1 h, while the equilibrium pH decreased by 2 units compared with CCD without carbonation. The carbonation of CCD formed nano calcite of lower decomposition temperature and also hampered the hydroxylation to decrease the effluent pH. The experimental results displayed carbonation can control the physicochemical property of the CCD, and the carbonated product is potential to be used for the removal of Cd (II) from aqueous solution.

•Sodium alginate reduced the crystal growth rate of struvite significantly.•Sodium alginate can adsorb and subsequently block active growth sites in the surface of struvite forming.•The adsorption of Sodium alginate on the surface of struvite crystals obeys Langmuir adsorption model.•Sodium alginate only affects the crystallization kinetics of struvite, causing no change in the mechanism of crystal growth.•Sodium alginate has a strong negative effect on the settleability of struvite crystals.As a representative of extracellular polymeric substances (EPS), the effect of sodium alginate (SA) crystallization kinetics of struvite, was investigated by constant composition technique under the conditions of 25 °C, pH 8.5, ion strength 0.1 mol L−1 NaCl. The results indicated that SA reduced the crystal growth rate of struvite significantly, attributed to the adsorption of SA and subsequently blocking of active growth sites onto the surface of struvite forming. Moreover, the adsorption followed Langmuir adsorption isotherm model, from which the affinity constant was calculated to be 63.6 × 104 L mol−1. Furthermore, SA in supersaturated solution affects the crystallization kinetics of struvite without changing its crystal growth mechanism. Additionally, SA can make the surface charge of struvite more negative, thus obviously reduce the settleability of struvite.

•We tested the hematite derived from thermally treated natural limonite for catalytic cracking of toluene.•Hematite played a role of oxygen carrier in reacting with carbon deposit.•The catalysts can be magnetically reclaimed after catalytic reaction.•The spent catalyst can be regenerated simply by thermal treatment under air atmosphere.The catalytic performance of hematite derived from thermally treated natural limonite on catalytic cracking of biomass tar using toluene as a model compound was investigated. The catalysts before and after catalytic reaction were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Magnetic Susceptibility meter (MS). The effect of reaction temperature and gas hourly space velocity (GHSV) on the catalytic performance of the newly formed hematite was studied in a laboratory scale fixed bed reactor. Furthermore, the composition of gas product was measured by gas chromatograph (GC) and the lifetime as well as the regeneration times was also evaluated. The results showed that the newly formed hematite had a high catalytic activity for the decomposition of toluene compared with that of quartz at the designed experimental temperature between 500 and 800 °C. The toluene conversion of 90% was obtained as the GHSV was not more than 5662 h−1 at the reaction temperature of 700 °C. Meanwhile, the toluene was mainly decomposed into H2, CO2, CO and hematite was transformed into magnetite after catalytic cracking. What is more important, the spent catalysts can be reclaimed easily by a magnet, which benefited the recycle and regeneration of the catalyst. In addition, the strong resistance of this hematite to carbon deposit in lifetime test due to the existence of active lattice oxygen in hematite was documented. Therefore, this kind of low cost and high activity hematite derived from natural limonite is considered to be an advantageous catalyst for catalytic cracking of toluene.

•The TiO2/goethite/palygorskite photocatalytic composite was prepared and analyzed.•TiO2/goethite/palygorskite composite exhibited good photocatalytic synergistic effect.•Electron–holes and oxygen synergy effect were responsible for benzene degradation.The nano-TiO2/goethite/palygorskite catalysts were prepared by sol–gel method. The morphology and structure of the catalysts were analyzed by X-ray diffraction (XRD), UV–Vis reflection spectrometer, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and N2 adsorption-desorption measurement. The results indicated that the self-made catalysts had excellent catalytic performance on gaseous benzene degradation. In the case of benzene concentration at 30 mg/m3, the degradation efficiency, over TiO2/goethite/palygorskite composite with mass ratio of 10:5:5, reached 70.4% after 180 min 254 nm UV irradiation. The reaction mechanism and kinetics study showed that palygorskite/goethite/TiO2 composites photocatalytic degradation benzene was mainly caused by oxidizing property of electron–holes and oxygen synergy effect.

Nano zero valent iron (NZVI) was prepared by reducing natural limonite using hydrogen. X-ray fluorescence, thermogravimetry, X-ray diffraction, transmission electron microscope, temperature programmed reduction (TPR), field emission scanning electron microscope/energy disperse spectroscopy (FESEM/EDS) were utilized to characterize the natural limonite and reduced limonite. The ratios of Fe:O before and after reducing was determined using EDS. The reactivity of the NZVI was assessed by decomposition of p-nitrophenol (p-NP) and was compared with commercial iron powder. In this study, the results of TPR and FESEM/EDS indicated that NZVI can be prepared by reducing natural limonite using hydrogen. Most importantly, this NZVI was proved to have a good performance on decomposition of p-NP and the process of p-NP decomposition agreed well with the pseudo-first-order kinetic model. The reactivity of this NZVI for decomposition of p-NP was greatly superior to that of commercial iron powder.

•p-NP was the predominant product of the photochemical reaction of HNO3 and benzene.•p-NP produced from α-Fe2O3 surface was much higher than that in the gas phase.•Photochemical reaction on particle surface was an important source to form SOA.The 308 nm photochemical reactions of nitric acid (HNO3) and benzene in the gas phase and on α-Fe2O3 surface at 298 K was investigated by using Fourier transform infrared spectroscopy (FT-IR) combined with high performance liquid chromatography (HPLC). The concentration and yield of HONO and p-nitrophenol (p-NP) had been examined as a function of reaction time, benzene initial concentration and relative humidity on photochemical reaction. The results showed that gaseous HNO3 did not directly react with benzene in the dark, and p-NP was formed irradiation under 308 nm UV light. When HNO3 initial concentration was 400 Pa and benzene was 300 Pa, the illumination time was 100 min, the concentration of p-NP produced from the photochemical reaction of HNO3 and benzene on α-Fe2O3 surface was about 3.08 times higher than that in the gas phase. In the meantime, while reaction time was 40 min and relative humidity was 70%, the concentration of HONO and p-NP formed on α-Fe2O3 surface were about 3.55 and 2.51 times higher than those in the gas phase, and the yield of p-NP was 3.74% and 2.99%, respectively. Surfaces effect played a leading role in photochemical reaction of HNO3 and benzene on α-Fe2O3 surface.

Natural pyrite was modified by calcination under nitrogen (N2) atmosphere to produce a novel sorbent for removing phosphorus (P) with low concentration from aqueous solutions. The crystallinity, porous texture, magnetic susceptibility and performance in P removal of pyrite calcinates depended on calcination temperatures. The sorbent obtained at calcination temperature of 500–600 °C possessed the most efficient P removal. Solution pH in the range of 3.0–9.0 and anions of chloridion (Cl−), nitrate (NO3)− and sulfate (SO42−) had ignorable effect on P removal. The batch adsorption experiment shows that the maximum sorption capacities for P of this novel sorbent (qm) were up to 1.61–5.36 mg P/g at adsorption temperatures of 15–35 °C. Dynamic sorption and regeneration experiments were conducted in an adsorption column filled with pyrite calcined at 600 °C. The study found that oxygen was an important control factor responsible for P adsorption because the oxidization of Fe2+ to Fe3+ on the surface of the sorbent followed by P being bound to a ferric hydroxide surface film was the crucial processes. The mechanism was confirmed with surface characterization techniques including field emission scanning electron microscope and X-ray photoelectron spectroscopy. This research potentially provides a cheap, abundant sorbent for P removal from the secondary effluent of municipal wastewater treatment plant.

•We have prepared palygorskite-supported Fe and Ni catalysts.•Catalytic cracking of rape straw is used to reduce tar content in biomass gasification gas.•Combustible gas derived from the pyrolysis increased with an increase in gasification temperature.Biomass tar restricts the wide application and development of biomass gasification technology. In the present paper, palygorskite, a natural magnesium-containing clay mineral, was investigated for catalytic pyrolysis of rape straw in situ and compared with the dolomite researched widely. The two types of natural minerals were characterized with XRD and BET. The results showed that combustible gas derived from the pyrolysis increased with an increase in gasification temperature. The Hconversion and Cconversion increased to 44.7% and 31% for the addition of palygorskite and increased to 41.3% and 31.3% for the addition of dolomite at the gasification temperature of 800 °C, compared with 15.1% and 5.6% without addition of the two types of material. It indicated that more biomass was converted into combustible gases implying the decrease in biomass tar under the function of palygorskite or dolomite and palygorskite had a slightly better efficiency than that of dolomite in the experimental conditions.Graphical abstract

Modified pyrite (MPy) with submicrometer particle sizes and porous polycrystalline structure, which was obtained by calcining pyrite, was used to remove and recover Cu, Pb, Cd, and Zn from the single- and multimetal fixed-bed columns. Results showed that the removal capacities of Cu and Pb were 77.42 and 73.68 mg/g MPy for single-metal solutions, and they were 30.79 and 10.86 mg/g MPy for the Cu–Pb–Cd–Zn multimetal solution. The Cu and Pb contents in the used MPy collected from the saturation zone of the single- and multimetal sorption columns were 17.4% and 15.37% and 6.8% and 2.5%, respectively, high enough to extract Cu and Pb from the used MPy particles by means of direct extractive metallurgy. This research shows that MPy is able to remove and recover Cu and Pb from wastewater even with the presence of Cd and Zn. Sequential extraction of the metals, XRD, and TEM analyses evidenced that the major mechanism for Cu and Pb removal by MPy was precipitation and dissolution reactions by formation of covellite and galena.

Sulfide sulfur, an important indicator for environmental monitoring and anaerobic bioengineering, has attracted increasing attention because of its significance in the anaerobic biotreatment processes and its high toxicity to humans and aquatic microorganisms. A detection system was designed for rapid and accurate determination of sulfide sulfur in an anaerobic system by gas-phase molecular absorption spectrometry (GPMAS). On the basis of the maximum absorption of hydrogen sulfide (H2S) at 202.6 nm, the calibration curve between sulfide content and absorbance was obtained, and then used to calculate the sulfide concentration in samples. The simulated samples of landfill leachate were used for detection after the anaerobic reaction. A new method for the removal of the effects of interference ions on the determination of sulfide in the fermentation broth is proposed. The results showed that the method obtained satisfactory precision and recovery. The detection limit of H2S in biogas is 5.1 × 10−3 mg L−1, the quantification limit is 1.7 × 10−2 mg L−1; in fermentation broth the detection limit of S2− is 1.2 × 10−2 mg L−1, the quantification limit is 4.1 × 10−2 mg L−1; the detection limit of acid volatile sulfide (AVS) in the fermentation residue is 2.7 × 10−2 mg g−1 (dry sample) and the quantification limit is 8.9 × 10−2 mg g−1 (dry sample). This indicates that the proposed method is suitable for the determination of sulfide sulfur derived from anaerobic systems.

•We have characterized the thermal transformation of natural goethite.•The heated products showed a topotactical relationship to the original mineral.•The N2 adsorption isotherm provided the variation of surface area and pore size distribution with temperature.•The significant increase in surface area was attributed to the formation of regularly arranged slit-shaped micropores.•The hematite derived from heating goethite has application as an adsorbent and catalyst.XRD (X-ray diffraction), XRF (X-ray fluorescence), TG (thermogravimetry), FT-IES (Fourier transform infrared emission spectroscopy), FESEM (field emission scanning electron microscope), TEM (transmission electron microscope) and nitrogen–adsorption–desorption analysis were used to characterize the composition and thermal evolution of the structure of natural goethite. The in situ FT-IES demonstrated the start temperature (250 °C) of the transformation of natural goethite to hematite and the thermodynamic stability of protohematite between 250 and 600 °C. The heated products showed a topotactic relationship to the original mineral based on SEM analysis. Finally, the nitrogen–adsorption–desorption isotherm provided the variation of surface area and pore size distribution as a function of temperature. The surface area displayed a remarkable increase up to 350 °C, and then decreased above this temperature. The significant increase in surface area was attributed to the formation of regularly arranged slit-shaped micropores running parallel to elongated direction of hematite microcrystal. The main pore size varied from 0.99 nm to 3.5 nm when heating temperature increases from 300 to 400 °C. The hematite derived from heating goethite possesses high surface area and favors the possible application of hematite as an adsorbent as well as catalyst carrier.

A zeolite porous filter (ZPF) was prepared using mixed raw zeolite, cement, and aluminum powder through steam curing and used as a novel filter medium in biological aerated filter (BAF). The performances of ZPF and commercially available ceramsite (CAC) in two laboratory scale upflow BAFs were compared. Results showed that the interconnected porous structure of ZPF was conducive to microbial biofilm growth. ZPF featured a total porosity of 29.55%, a compressive strength of 41–47 N, and a specific surface area of 59.53 m2/g. BAF containing ZPF showed more effectively the removal of organic carbon, ammonia nitrogen, nitrogen, and phosphorus compared to BAF containing CAC. The hydraulic retention time (HRT) was 7 h at an air/water (A/W) ratio of 3:1. The amounts of total nitrogen removed were 59.89% with ZPF and 35.96% with CAC. Moreover, the amount of phosphorus removed was 83.80% with ZPF, whereas that of CAC was only 31.50%. ZPF was more suitable for the attached growth of heterobacteria and nitrobacteria to attain simultaneous nitrification and denitrification performance in the BAF. Therefore, ZPF is a novel suitable filter medium for simultaneous removal of nitrogen and phosphorus in BAFs.Download high-res image (169KB)Download full-size image

The filter medium plays an important role in modulating the performance of biological aerated filters (BAFs). In this study, a zeolite composite filter (ZCF) was fabricated using a mixture of natural zeolite powder as the main material, cement as the binder, and waste paper pulp as the pore-forming agent (slow-release carbon source). Scanning electron microscopy and porosimetry were then conducted to evaluate the properties of the ZCF. Results showed that the uniform and interconnected pores of the ZCF are suitable for microbial growth. ZCF and commercially available ceramsite (CAC) used in an upflow laboratory-scale BAF were investigated to determine their suitability for advanced wastewater treatment. The results indicated that the ZCF–BAF is superior to the CAC–BAF in terms of total organic carbon, total nitrogen, ammonia nitrogen, and phosphorus removal. The carbon source from the waste paper pulp was released slowly, which decisively influenced simultaneous nitrification and denitrification. Therefore, ZCF is suitable for use as a novel filter medium for the simultaneous removal of nitrogen and phosphorus in BAFs for advanced wastewater treatment.

•A novel sorbent was manufactured by calcination of natural colloidal pyrite.•Cu removal by the novel sorbent was examined in a fixed bed column.•The throughput volume of the sorbent was up to 1672 bed volumes.•Cu content in the bottom reacted sorbent was up to 20%, benefiting Cu recovery.•The main removal mechanism for Cu was the formation of CuS precipitate.The aim of this study was to investigate the capacity and mechanism of a novel and cost-effective sorbent for copper (Cu) removal and recovery from wastewater. Calcined colloidal pyrite (CCPy) was prepared by calcining natural colloidal pyrite mineral in a N2 atmosphere. Cu2 + removal from aqueous solutions by using iron sulfides was investigated with fixed-bed column experiments. Results show that CCPy was much more efficient in Cu2 + removal than other three iron sulfide sorbents (natural pyrite, colloidal pyrite, and pyrrhotite). When the influent Cu2 + concentration was 1.56 mmol/L and Cu2 + breakthrough concentration was 0.0078 mmol/L, the throughput volume of the CCPy column was up to 1672 bed volumes (BV); the sorption amount at breakthrough was 84 mg Cu/g CCPy. The maximum Cu content in the used CCPy sorbent was up to 20%, which is much higher than the grades of industrial Cu ore (0.4–2.8%), indicating that CCPy can be used as an effective sorbent for the recovery of Cu2 + from wastewater. Copper specification analysis, X-ray diffraction (XRD), and transmission electron microscopy (TEM) show that Cu removal by CCPy was mainly due to the formation of covellite on the CCPy's surface. The CCPy sorbent has advantages over chemical precipitation and other sorbents due to the recovery of Cu from wastewater, cheap raw material for manufacturing this sorbent, and prevention of hazardous sludge generation.Download full-size image

Sulfide sulfur, an important indicator for environmental monitoring and anaerobic bioengineering, has attracted increasing attention because of its significance in the anaerobic biotreatment processes and its high toxicity to humans and aquatic microorganisms. A detection system was designed for rapid and accurate determination of sulfide sulfur in an anaerobic system by gas-phase molecular absorption spectrometry (GPMAS). On the basis of the maximum absorption of hydrogen sulfide (H2S) at 202.6 nm, the calibration curve between sulfide content and absorbance was obtained, and then used to calculate the sulfide concentration in samples. The simulated samples of landfill leachate were used for detection after the anaerobic reaction. A new method for the removal of the effects of interference ions on the determination of sulfide in the fermentation broth is proposed. The results showed that the method obtained satisfactory precision and recovery. The detection limit of H2S in biogas is 5.1 × 10−3 mg L−1, the quantification limit is 1.7 × 10−2 mg L−1; in fermentation broth the detection limit of S2− is 1.2 × 10−2 mg L−1, the quantification limit is 4.1 × 10−2 mg L−1; the detection limit of acid volatile sulfide (AVS) in the fermentation residue is 2.7 × 10−2 mg g−1 (dry sample) and the quantification limit is 8.9 × 10−2 mg g−1 (dry sample). This indicates that the proposed method is suitable for the determination of sulfide sulfur derived from anaerobic systems.