A study of the kinetics and the effect of trace elements on mixed anaerobic fermentative biogas production by ternary quadratic general rotary unitized design

In this study the effect of trace elements on methanogenesis was investigated during mixed anaerobic fermentation using a single-factor experiment in the present study. The most effective concentrations of Fe0, Fe2+, Co2+ and Ni2+ that were added were 1500, 250, 0.3 and 0.6 mg/L, respectively. The optimal trace element combination was 0.58 mg/L Ni2+, 1200 mg/L Fe0 and 0.34 mg/L Co2+ by the ternary quadratic general rotary unitized design method. The degree of influence exerted by trace elements on the cumulative methane yields decreased in the order of Ni2+, Fe0 and Co2+, and the maximum CH4 yield was 241.6 mL/g volatile solids (VS), according to a regression equation. The non-dissolved organic carbon hydrolytic process showed a good fit with the first-order kinetic model. The maximum value of CH4 was 312.87 mL/g VS. Compared to the control, the bioconversion efficiencies of CH4 and CO2 production increased by 36.76% and 74.50%, respectively, at the optimal trace element combination. The obtained results provide new knowledge for improvements in the efficiency of anaerobic fermentation biogas production

Effect of different ratios of cow manure and corn straw on the mixed anaerobic fermentation rate

In order to study the effect of the different ratios on the anaerobic fermentation rate is investigated, and the rate-limiting factors are preliminarily determined, at mesophilic (38±1)℃ condition, with anaerobic granular sludge as inoculums, different ratios of cow manure and corn straw are used as substrate for mixed anaerobic fermentation. By measuring daily biogas production, the concentrations of CH4 and CO2 in the marsh gas, TC, the concentration of VFAs and pH value, The results show that under the mixture ratio of 2∶1, the hydrolysis rate constants, cumulative biogas yield and biodegradability CH4 reach their high limits, which are 0.043 7 d<sup>-1</sup>, 271.93 mL/g and 71.59%, respectively. Moreover, it is found that the concentration of acetic acid is proportional to the amount of cow manure at the beginning (the first day) of mixed fermentation, and the concentration of propionicacid is proportional to the amount of corn straw in medium fermentation stage (the fifth day). In addition, rate-limiting step of biogas production is related to the ratio of cow manure and corn in fermentation material. With the increasing of corn straw proportion, on the 1st day, it tends to hydrolysis acidogenesis; from the 2th day to 15th day, it tends to hydrogen-production acetogenisis; and from the 16th day to 30th day, it is hydrolysis acidogenesis. The paper focuses on the relationship between the ratio of cow manure and corn straw and the rate-limiting step for biogas production, which could provide a theoretical and experimental support for improving the efficiency of biogas production in mixed fermentation

Efficient and selective immobilization of Pb2+ in highly acidic wastewater using strontium hydroxyapatite nanorods

In this paper, strontium hydroxyapatite (Sr5(PO4)3(OH), SrHAp) nanorods were synthesized by a hydrothermal method and utilized for immobilization of Pb2+ from acidic aqueous solutions. The SrHAp nanorods exhibited a high immobilization capacity of 1482 ± 137 mg g!1 for Pb2+ in acidic solutions (pH = 2.5) within 15 min. The SrHAp nanorods could selectively immobilize Pb2+ with little immobilization effect on other co-existing metal ions when they were used to treat highly acidic nonferrous metallurgy wastewater (pH = 1.1). The XRD, SEM, EDX and XPS results revealed that the immobilization of Pb2+ by the SrHAp nanorods was mainly due to ion exchange and Pb2+ precipitation

Occurrence and profiles of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in soils from a typical e-waste recycling area in Southeast China

Surface soils collected from Taizhou, a typical e-waste recycling area in Southeast China, were analyzed for the residues of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs) by using microwave-assisted extraction and gas chromatography -mass spectrometry (GC-MS). The total concentrations of 16 PAHs in US EPA's priority list (Sigma PAHs), six indicator PCBs (Sigma PCBs), 15 OCPs widely used in China (Sigma OCPs) in soils ranged from 125 to 4737 ng/g (average: 854 ng/g), from not detected to 55.4 ng/g (3.16 ng/g), and from 47.9 to 820 ng/g (276 ng/g), respectively. Individual PAHs were ubiquitously found in soil samples with detected ratio of 96% and their residual levels were comparable with those of serious polluted sites. Principal component analysis in combination with diagnostic ratios suggested that the combustion of coal, wood, and plastic wastes that are closely associated with illegal and unsafe recycling operations of e-wastes was the main source of PAHs in this area. Compared with other polluted sites, the PCBs residues in soils were generally low except for those in the major recycling site. The residual levels of OCPs in this region were also relatively higher and hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane (DDT) and its metabolite forms including dichlorodiphenyldichloroethane (DDD) and dichlorodiphenyldichloroethylene (DDE), hexachlorobenzene (HCB), and dicofol were dominant species. The composition analysis indicated that the HCHs residues in soils might originate from the application of lindane (pure gamma-HCH) and parts of DDTs possibly from the wide use of dicofol with high impurity of DDT compounds in this region.Surface soils collected from Taizhou, a typical e-waste recycling area in Southeast China, were analyzed for the residues of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs) by using microwave-assisted extraction and gas chromatography -mass spectrometry (GC-MS). The total concentrations of 16 PAHs in US EPA's priority list (Sigma PAHs), six indicator PCBs (Sigma PCBs), 15 OCPs widely used in China (Sigma OCPs) in soils ranged from 125 to 4737 ng/g (average: 854 ng/g), from not detected to 55.4 ng/g (3.16 ng/g), and from 47.9 to 820 ng/g (276 ng/g), respectively. Individual PAHs were ubiquitously found in soil samples with detected ratio of 96% and their residual levels were comparable with those of serious polluted sites. Principal component analysis in combination with diagnostic ratios suggested that the combustion of coal, wood, and plastic wastes that are closely associated with illegal and unsafe recycling operations of e-wastes was the main source of PAHs in this area. Compared with other polluted sites, the PCBs residues in soils were generally low except for those in the major recycling site. The residual levels of OCPs in this region were also relatively higher and hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane (DDT) and its metabolite forms including dichlorodiphenyldichloroethane (DDD) and dichlorodiphenyldichloroethylene (DDE), hexachlorobenzene (HCB), and dicofol were dominant species. The composition analysis indicated that the HCHs residues in soils might originate from the application of lindane (pure gamma-HCH) and parts of DDTs possibly from the wide use of dicofol with high impurity of DDT compounds in this region

Source and Migration of Short-Chain Chlorinated Paraffins in the Coastal East China Sea Using Multiproxies of Marine Organic Geochemistry

Multiple proxies of terrestrial organic matters (TOM) were introduced to study the migration behaviors of short-chain chlorinated paraffins (SCCPs) in the coastal East China Sea (ECS). The contents of SCCPs in the surface sediment collected from Changjiang (Yangtze) River Delta (CRD) and along the Zhejiang–Fujian coastline ranged from 9.0 to 37.2 ng/g (dry weight, d.w.), displaying a “band-style” distribution trend. Spatial distribution patterns of SCCP congeners presented an increasing trend seaward and southward along the coastline for shorter carbon length (C₁₀ + C₁₁) and lower chlorinated (Cl₅ + Cl₆ + Cl₇) congeners, suggesting a spreading tendency seaward and southward from the CRD and the north of the inner shelf. The significant relationship between ΣSCCPs and total organic carbons (TOC) (<i>r</i>² = 0.402, <i>p</i> < 0.05) indicated that the migration of SCCPs in sediments was markedly affected by TOC. The spatial patterns of the TOM proxies of TOC δ¹³C, the contents of ΣC₂₇ + C₂₉ + C₃₁ <i>n</i>-alkanes, terrestrial marine biomarker ratio (TMBR), and terrestrial TOC (T-TOC) were all similar to that of ΣSCCPs. Linear relationships between SCCP contents and both the contents of ΣC₂₇ + C₂₉ + C₃₁ <i>n</i>-alkanes (<i>r</i>² = 0.537, <i>p</i> < 0.05) and T-TOC (<i>r</i>² = 0.495, <i>p</i> < 0.05) were also observed. The consistence demonstrated that a major portion of sedimentary SCCPs in the coastal ECS should be from the river input of Changjiang River and deposited in the CRD and along the inner shelf of the ECS, but only a minor fraction was transported to the offshore areas

Spatial Distributions and Deposition Chronology of Short Chain Chlorinated Paraffins in Marine Sediments across the Chinese Bohai and Yellow Seas

As the most complex halogenated contaminants, short chain chlorinated paraffins (SCCPs) are scarcely reported in marine environments. In this work, a total of 117 surficial sediment (0–3 cm) samples and two sediment cores were collected from the Chinese Bohai and Yellow Seas to systematically study the spatial and temporal trends of SCCPs at a large scale in the Chinese marine environment. Total SCCP concentrations in the surficial sediments were in the range of 14.5–85.2 ng g^–1 (dry weight, d.w.) with an average level of 38.4 ng g^–1 d.w. Spatial distribution showed a decreasing trend with the distance from the coast to the open waters. Compositional pattern analysis suggested that C₁₀ was the most predominant homologue group, followed by C₁₁, C₁₂, and C₁₃ homologue groups. The concentrations of total SCCPs in sediment cores ranged from 11.6 to 94.7 ng g^–1 d.w. for YS1 and from 14.7 to 195.6 ng g^–1 d.w. for YS2, with sharp rise from the early 1950s to present based on ²¹⁰Pb dating technique. The historical records in cores correspond well to the production and usage changes of CPs in China. Multivariate regression statistics indicate TOC, latitude and longitude are the major factors influencing surficial SCCP levels in the Chinese East Seas by combining analysis with the data from the East China Sea (<i>R</i>² = 0.332, <i>p</i> < 0.01). These findings indicated that the sources of SCCPs were mainly from river outflows via ocean current and partly from atmospheric depositions by East Asian monsoon in the sampling areas

AuFe₃@Pd/γ-Fe₂O₃ Nanosheets as an In Situ Regenerable and Highly Efficient Hydrogenation Catalyst

Heterogenous Pd catalysts play a pivotal role in the chemical industry; however, it is plagued by S2– or other strong adsorbates inducing surface poisoning long term. Herein, we report the development of AuFe3@Pd/γ-Fe2O3 nanosheets (NSs) as an in situ regenerable and highly active hydrogenation catalyst. Upon poisoning, the Pd monolayer sites could be fully and oxidatively regenerated under ambient conditions, which is initiated by •OH radicals from surface defect/FeTetra vacancy-rich γ-Fe2O3 NSs via the Fenton-like pathway. Both experimental and theoretical analyses demonstrate that for the electronic and geometric effect, the 2–3 nm AuFe3 intermetallic nanocluster core promotes the adsorption of reactant onto Pd sites; in addition, it lowers Pd’s affinity for •OH radicals to enhance their stability during oxidative regeneration. When packed into a quartz sand fixed-bed catalyst column, the AuFe3@Pd/γ-Fe2O3 NSs are highly active in hydrogenating the carbon–halogen bond, which comprises a crucial step for the removal of micropollutants in drinking water and recovery of resources from heavily polluted wastewater, and withstand ten rounds of regeneration. By maximizing the use of ultrathin metal oxide NSs and intermetallic nanocluster and monolayer Pd, the current study demonstrates a comprehensive strategy for developing sustainable Pd catalysts for liquid catalysis

Distribution of Short Chain Chlorinated Paraffins in Marine Sediments of the East China Sea: Influencing Factors, Transport and Implications

Short chain chlorinated paraffins (SCCPs) are high production volume chemicals in China and found to be widely present in the environment. In this study, fifty-one surface sediments and two sediment cores were collected from the East China Sea to study their occurrence, distribution patterns and potential transport in the marginal sea. SCCPs were found in all surface sediments and ranged from 5.8 to 64.8 ng/g (dry weight, d.w.) with an average value of 25.9 ng/g d.w. A general decreasing trend with distance from the coast was observed, but the highest value was found in a distal mud area far away from the land. The C10 homologue was the most predominant carbon chain group, followed by C11, C12, and C13 homologue groups. Significant linear relationship was found between total organic carbon (TOC) and total SCCP concentrations (<i>R</i>² = 0.51, <i>p</i> < 0.05). Spatial distributions and correlation analysis indicated that TOC, riverine input, ocean current, and atmospheric deposition played an important role in controlling SCCP accumulation in marine sediments. Vertical profiles of sediment cores showed that SCCP concentrations decreased from surface to the depth of 36 cm, and then slightly increased again with depth, which showed a significant positive correlation with TOC and chlorine contents (Cl%). The results suggest that SCCPs are being regionally or globally distributed by long-range atmospheric or ocean current transport