Organic removal from coal-to-chemical brine by a multistage system of adsorption-regeneration and electrochemically driven UV/chlorine processes.

Treatment of coal-to-gas brine (CGB) is a great challenge since it contains elevated inorganic salts and a high level of toxic and bio-accumulative organics. In this study, CGB treatment was conducted by adsorptionregeneration and electrochemically driven UV/chlorine (E-UV/Cl2) processes. LS-109D macroporous resin was optimal adsorbent primarily due to unique pore structure, which preferably adsorbed the aromatic fluorescent components with quenching Cl∙ effect and low molecular weight acids recalcitrant to ∙OH. The E-UV/Cl2 process outperformed the UV photolysis process and electrochemical advanced oxidation processes (EAOPs) for oxidation of organic compounds due to its full utilization of Cl- in CGB to produce highly active oxidation agents. Thanks to the synergy between process units in organic matter removal, dissolved organic carbon (DOC) of CGB was reduced from 163.41 mg/L to 26.58 mg/L by the multistage system. Furthermore, the CGB with characteristics of high fluorescence and molecular weight (MW) distribution was converted to effluent with low fluorescence and MW distribution. The exhausted LS-109D was regenerated by ultrasound-assisted hot water elution at 363 K. After pretreated by ozonation, the eluate can be easily treated by biological process. The study suggests that the multistage system can provide an effective treatment option for removing organics from CGB.

Temporal relationship between serial RT-PCR results and serial chest CT imaging, and serial CT changes in coronavirus 2019 (COVID-19) pneumonia: a descriptive study of 155 cases in China.

OBJECTIVE: To determine CT's role in the early detection of COVID-19 infection and serial CT changes in the disease course in patients with COVID-19 pneumonia. METHODS: From January 21 to February 18, 2020, all of the patients who were suspected of novel coronavirus infection and verified by RT-PCR tests were retrospectively enrolled in our study. All of the patients underwent serial RT-PCR tests and serial CT imaging. The temporal relationship between the serial RT-PCR results (negative conversion to positive, positive to negative) and serial CT imaging was investigated, and serial CT changes were evaluated. RESULTS: A total of 155 patients with confirmed COVID-19 pneumonia were evaluated. Chest CT detection time of COVID-19 pneumonia was 2.61 days earlier than RT-PCR test (p = 0.000). The lung CT improvement time was significantly shorter than that of RT-PCR conversion to negative (p = 0.000). Three stages were identified from the onset of the initial symptoms: stage 1 (0-3 days), stage 2 (4-7 days), and stage 3 (8-14 days and later). Ground glass opacity (GGO) was predominant in stage 1, then consolidation and crazy paving signs were dramatically increased in stage 2. In stage 3, fibrotic lesions were rapidly increased. There were significant differences in the main CT features (p = 0.000), number of lobes involved (p = 0.001), and lesion distribution (p = 0.000) among the different stages. CONCLUSION: Chest CT detected COVID-19 pneumonia earlier than the RT-PCR results and can be used to monitor disease course. Combining imaging features with epidemiology history and clinical information could facilitate the early diagnosis of COVID-19 pneumonia. KEY POINTS: • The chest CT detection time of COVID-19 pneumonia was 2.61 days earlier than that of an initial RT-PCR positive result (t = - 7.31, p = 0.000). • The lung CT improvement time was significantly shorter than that of RT-PCR conversion to negative (t = - 4.72, p = 0.000). • At the early stage (0-3 days), the CT features of COVID-19 were predominantly GGO and small-vessel thickening; at stage 2 (4-7 days), GGO evolved to consolidation and crazy paving signs. At stage 3 (8-14 days and later), fibrotic lesions significantly increased, accompanied by consolidation, GGO, and crazy paving signs.

Effect of Different Acid-Modified Coking Coals on Quinoline Adsorption.

The adsorption of quinoline from wastewater by coking coal (AC-1), HCl-modified coking coal (AC-2), HNO3-modified coking coal (AC-3), HF-modified coking coal (AC-4), and H2SO4-modified coking coals (AC-5) was investigated in this paper. The effects of acid-modified concentration, modification time, and adsorption time versus quinoline removal rate were studied by batch experiments. The quinoline concentration was measured by UV spectrophotometry, the average pore size and specific surface area of coking coal before and after modification were characterized through static nitrogen adsorption, the mineral composition of coking coal was tested by X-ray diffraction, the surface functional groups were tested by Fourier transform infrared spectroscopy, and the surface topography was tested using a scanning electron microscope. The experimental results showed that the adsorption capacity of coking coals was the best when both the modification time was 120 min and the acid-modified concentration was 0.1 mol·L-1 and the quinoline removal rate reaches the highest when the adsorption time was 120 min. The specific surface area of AC-2 increased from 2.898 to 3.637 m2·g-1, and the removal rate of quinoline increased from 77.64 to 90.61%. Acids reacted with inorganic mineral impurities within coking coal such as hydrogen vanadium phosphate hydrate, which caused an increase in the specific surface area. A new peak appeared in the Fourier transform infrared spectroscopy pattern at the wavenumber 2300 cm-1. The surface of coking coal modified by acids was rougher than that of AC-1. The adsorption capacity of coking coal was improved after modification, and modified coking coals have the highest potential as low-cost adsorbents for quinoline removal.

Effects and mechanistic aspects of absorbing organic compounds by coking coal.

Coal is a porous medium and natural absorbent. It can be used for its original purpose after adsorbing organic compounds, its value does not reduce and the pollutants are recycled, and then through systemic circulation of coking wastewater zero emissions can be achieved. Thus, a novel method of industrial organic wastewater treatment using adsorption on coal is introduced. Coking coal was used as an adsorbent in batch adsorption experiments. The quinoline, indole, pyridine and phenol removal efficiencies of coal adsorption were investigated. In addition, several operating parameters which impact removal efficiency such as coking coal consumption, oscillation contact time, initial concentration and pH value were also investigated. The coking coal exhibited properties well-suited for organics' adsorption. The experimental data were fitted to Langmuir and Freundlich isotherms as well as Temkin and Redlich-Peterson (R-P) models. The Freundlich isotherm model provided reasonable models of the adsorption process. Furthermore, the purification mechanism of organic compounds' adsorption on coking coal was analysed.

Retention and distribution of Cu, Pb, Cr, and Zn in a full-scale hybrid constructed wetland receiving municipal sewage.

This study was conducted to investigate the retention and distribution of Cu, Pb, Cr, and Zn in a hybrid constructed wetland (CW) that consists of both vertical baffled flow wetlands (VBFWs) and horizontal subsurface flow wetlands (HSSFs) with unique flow regimes and oxygen distribution. The heavy metal concentrations in water, sediments, and plant tissues in the hybrid CW were analysed. The removal of heavy metals from the water stream in the monitoring period was not statistically significant. Metal concentrations in the sediments generally decreased along the wastewater treatment process. The reductive anaerobic condition in the VBFW may promote the sulphate reduction and form highly insoluble Cu, Pb, and Zn sulphides, resulting in the higher concentration of the bivalent cations in the VBFW sediments than the corresponding values in the HSSF; however, the aerobic and anoxic environments in the HSSF enhanced the removal of Cr with the co-precipitation of iron and manganese oxides, and their hydroxides. Metal concentrations in plant tissues were not significantly influenced by the concentrations in sediments, while roots contained statistically higher metal concentrations than stems and leaves. The sediments stored 94.01, 86.31, 95.85, and 89.51% of the total Cu, Pb, Cr, and Zn retained in the hybrid CW system, respectively, while only small fractions (<10%) were accumulated in the harvestable macrophyte tissues. It is important to clean not only the accessible sediments in free water surface tank and ponds but also the embedded sediments in vegetated beds for the sustainable removal of heavy metals.

Variation of dissolved oxygen and redox potential and their correlation with microbial population along a novel horizontal subsurface flow wetland.

AIMS: This study was conducted to evaluate the performance of a novel horizontal subsurface flow wetland (HSFW) in naturally improving the dissolved oxygen (DO) and the impact on redox condition, microbial activity and the nitrogen removal in the HSFW bed. MATERIALS AND METHODS: The HSFW, equipped with cascaded natural aeration ditches (NADs), was the second stage of a hybrid constructed wetland (CW) after vertical-baffled flow wetland beds. The performances of the HSFW for organics and nitrogen removal in a full-scale hybrid CW system treating municipal wastewater for more than three years have been analysed. The spatial distributions of the oxidation-reduction potential (ORP), DO, microbial population density and specific oxygen uptake rate were determined, and their correlations were analysed in one selected section of the HSFW bed. RESULTS: A 7-m-long shallow NAD increased the DO concentration from 0.28 mg O2 L(-1) to 3.80 mg O2 L(-1) and the ORP from +37.3 mV to +247.7 mV, creating an aerobic zone with a hydraulic retention time (HRT) of 0.5 h and an anoxic zone of another 0.5 h in series in the subsequent wetland bed. For the whole HSFW with three NADs, the macro aerobic and anoxic environment with a total HRT of 3 h can be created. CONCLUSIONS: The unique DO distribution in HSFW may contribute to an optimum environment for partial nitrification and anammox, and obtain a high performance for nitrogen removal. Correlation analysis showed that the microbial activity in the HSFW relied obviously on the redox condition.