Assessment of the Greenhouse Gas Footprint and Environmental Impact of CO_(2)and O_(2)in situ Uranium Leaching

Under the new development philosophy of carbon peaking and carbon neutrality,CO_(2)and O_(2)in situ leaching(ISL)has been identified as a promising technique for uranium mining in China,not only because it solves carbon dioxide utilization and sequestration,but it also alleviates the environmental burden.However,significant challenges exist in assessment of CO_(2)footprint and water-rock interactions,due to complex geochemical processes.Herein this study conducts a three-dimensional,multicomponent reactive transport model(RTM)of a field-scale CO_(2)and O_(2)ISL process at a typical sandstone-hosted uranium deposit in Songliao Basin,China.Numerical simulations are performed to provide new insight into quantitative interpretation of the greenhouse gas(CO_(2))footprint and environmental impact(SO_(4)^(2–))of the CO_(2)and O_(2)ISL,considering the potential chemical reaction network for uranium recovery at the field scale.RTM results demonstrate that the fate of the CO_(2)could be summarized as injected CO_(2)dissolution,dissolved CO_(2)mineralization and storage of CO_(2)as a gas phase during the CO_(2)and O_(2)ISL process.Furthermore,compared to acid ISL,CO_(2)and O_(2)ISL has a potentially smaller environmental footprint,with 20%of SO_(4)^(2–)concentration in the aquifer.The findings improve our fundamental understanding of carbon utilization in a long-term CO_(2)and O_(2)ISL system and provide important environmental implications when considering complex geochemical processes.

High-performance ZIF-8 membranes:preparation and their uranium adsorption performance

In this study,the ZIF-8 membrane(ZIF-8/PP-g-MAH)is prepared by in situ synthesis of ZIF-8 on irradiation-pretreated polymer substrates to improve the uranium adsorption performance and address the recycling problems of ZIF-8 powder.The effects of pH,contact time,and uranium concentration on the adsorption of ZIF-8/PP-g-MAH were investigated.Adsorption isotherm and kinetics analysis show that ZIF-8/PP-g-MAH has a high adsorption capacity of 478.5 mg/g,which is 1.26 times higher than that of ZIF-8,and a rapid adsorption equilibrium of 120 min,which is shortened to one-third of that required for ZIF-8(360 min).The adsorption process of ZIF-8/PP-g-MAH is consistent with that of the Langmuir isotherm and pseudo-second-order dynamic model.ZIF-8/PP-g-MAH also exhibits good selectivity for uranium in simulated seawater.The high adsorption performance of ZIF-8/PP-g-MAH is attributed to its membrane structure,which improves the utilization of coordination sites,including Zn-OH,C-N,and C=N.This study provides an efficient adsorption material for rapid uranium extraction,thus promoting the development of uranium extraction technologies.

Characteristics and method of synthesis seismic wave based on wavelet reconstruction

A novel method of synthesizing seismic wave using wavelet reconstruction is proposed and compared with the traditional method of using theory of Fourier transform. By adjusting the frequency band energy and taking it as criterion, the formula of synthesizing seismic wave is deduced. Using the design parameters specified in Chinese Seismic Design Code for buildings, seismic waves are synthesized. Moreover, the method of selecting wavelet bases in synthesizing seismic wave and the influence of the damping ratio on synthesizing results are analyzed. The results show that the synthesis seismic waves using wavelet bases can represent the characteristics of the seismic wave as well as the ground characteristic period, and have good time-frequency non-stationary.

Unraveling the role of formate in improving nitrogen removal via coupled partial denitrification-anammox

The addition of traditional carbon sources(e.g.,acetate)could favor heterotrophic overgrowth in partial denitrification coupled with anammox(PD–A)systems,thus hindering the performance and stability of this novel wastewater nitrogen removal technology.Therefore,it is necessary to develop an effective,environmentally friendly,and inexpensive alternative.This study demonstrated the potential of formate to enhance the performance and community stability of PD–A under mainstream conditions.In a laboratory-scale biofilm reactor,formate addition(COD/NO_(3)^(–)–N=1.75)improved nitrogen removal efficiency(from 72.1±3.5%to 81.7±2.7%),EPS content(from 106.3±8.1 to 163.0±15.5 mg/gVSS)and increased anammox bacteria growth(predominantly Candidatus Brocadia,from 29.5±0.7%to 34.5±5.4%)while maintaining stable heterotrophs dominated by methylotrophic Desulfobacillus.FISH–NanoSIMS revealed a formate uptake using Ca.Brocadia and Desulfobacillus,with Ca.Brocadia being the major contributor to partial nitrate reduction to nitrite.Desulfobacillus can synthesize diverse hydrophobic amino acids and provide key nutrients for Ca.Brocadia.To achieve comparable nitrogen removal,the cost of the formate-driven PD–A process should be 11.2%lower than that of acetate.These results greatly enrich our understanding of C1 metabolism represented by formate in anammox communities and its application in the context of coupling partial denitrification–anammox toward enhanced nitrogen removal in global wastewater treatment systems.

A calibration-free model for laser-induced breakdown spectroscopy using non-gated detectors

Calibration-free(CF)laser-induced breakdown spectroscopy(LIBS)is normally only applicable for gated detectors due to its dependence on the assumption of a steady-state plasma.However,most currently available LIBS systems are equipped with non-gated detectors such as chargecoupled device(CCD),which degrades the accuracy of CF method.In this paper,the reason for the less satisfactory quantification performance of CF for LIBS with non-gated detectors was clarified and a time-integration calibration-free(TICF)model was proposed for applications with non-gated detectors.It was based on an assumed temporal profile of plasma properties,including temperature and electron density,obtained from another pre-experiment.The line intensity at different time during the signal collection time window was estimated with self-absorption correction according to the temporal profile of the plasma properties.The proposed model was validated on titanium alloys and compared with traditional CF.The accuracy of elemental concentration measurement was improved significantly:the average relative error of aluminum and vanadium decreased from 6.07%and 22.34%to 2.01%and 1.92%,respectively.The quantification results showed that TICF method was able to extend the applicability of CF to LIBS with non-gated detectors.