Lead sulfide (PbS) is the main component of galena. The traditional method used to prepare metal lead from galena is disadvantaged by high energy consumption and severe pollution. In this paper, an eco-friendly yet simple process is proposed to prepare high-purity metal lead directly from lead sulfide. According to thermodynamic calculation, lead sulfide can be decomposed into metal lead under vacuum. The pathway to decomposition is based on the reaction of 2PbS (s) = 2 Pb (l) + S 2 (g). Besides, an investigation was conducted into the impact of temperature and holding time on the quality of decomposition products and the purity of lead in residue. The investigative results show that the decomposition rate of lead sulfide reached its maximum at 1050 °C for 60 min, which is about 50%, and the purity of the lead in the residue reached 99.51%. When the temperature reached above 1100 °C and the holding time exceeded 40 min, the purity of lead reached as high as 99.81%, but the quality of the residue stayed low. This method contributes a fresh idea to the eco-friendly utilization and efficient purification of galena for preparing high-purity metal lead.
Because of its irreversible toxicity and harm to people's health, lead contamination has gotten a lot of attention. As a result, the development of low-cost, high-performance removal approaches has become a popular issue. In this work, novel metal-organic framework (AMO-MOF) was developed to selectively adsorb Pb(II) from water. AMO-MOF perfectly inherits the structural characteristics of mesoporous materials and its specific surface area is 255.251 m 2 /g. The adsorption reached equilibrium at 180 min and the maximum adsorption capacity of AMO-MOF for Pb(II) was 472.73 mg/g. The adsorption of Pb(II) on AMO-MOF was fitted with pseudo-second-order kinetics and Langmuir isotherm models, indicating that the adsorption was monolayer chemisorption process. Thermodynamic and activation energy ( Ea ) analyses indicate that the monolayer chemisorption of Pb(II) on AMO-MOF was an endothermic process. When multiple cations coexist, AMO-MOF exhibits excellent selectivity for Pb(II). Meanwhile, after repeated used for 5 times, the removal rate can still reach more than 80 %. The adsorption mechanism is mainly the chelation and electrostatic interaction of N and O-containing functional groups on the adsorbent with Pb(II). The excellent adsorption performance of AMO-MOF for Pb(II) makes it have great application potential in practical environmental remediation.
At present, solvent extraction is an effective method to remove heavy metals from soil, which has certain practical significance. The physical properties such as density, viscosity and conductivity of NADESs with different proportions synthesized based on the double solid components of glycolic acid (GA) and L-proline (L-PRO) and the physical properties of NADESs aqueous solution at the lowest eutectic point (3:1) were studied. The extraction effect of NADESs on soil heavy metal Pb 2+ under different conditions was studied. The results showed that under the conditions of atmospheric pressure of 101.33 kPa, the lowest eutectic melting point, DESs concentration of 0.6 mol·L −1 , extraction temperature of 313.15 K and extraction time of 4 h, the extraction rate of Pb 2+ by NADESs was 95.28%. In addition, the internal structure of DESs was characterized by IR and NMR, which indicated that intermolecular hydrogen bonds were formed. and the interaction between DESs and Pb 2+ was analyzed by quantum chemical calculation, which showed that the hydroxyl group of GA was more likely to form coordination bond with Pb 2+ , and chelation occurred between them. This kind of DESs provides a new idea for the removal of heavy metals in soil.
The worm-like nitrogen-doped-carbon framework (WNCF) with abundant edge-plane-like defective sites (EDSs) was synthesized by using natural wax gourd ( Benincasa hispida ) as the main carbon precursor and milk yielded by Chinese Holstein cattle ( Holstein Friesian ) as the nitrogen precursor for the first time. The Nafion-dispersed WNCF (Nafion-WNCF) was employed to design a highly sensitive electrochemical sensor for the trace determination of toxic heavy metal lead (II) (Pb 2+ ) by the differential pulse anodic stripping voltammetry (DPASV). Some key experimental factors including calcination temperature of WNCF, pH value of the buffer solution, deposition potential, deposition time and the concentration of bismuth (Bi 3+ ) were optimized for the stripping analysis of Pb 2+ . Under the optimum experimental condition, Nafion-WNCF modified bismuth film glassy carbon electrode (Nafion-WNCF/BFGCE) exhibits a wide linear range from 0.5 μg L −1 to 100 μg L −1 and a low detection limit of 0.2 μg L −1 (S/N = 3) for detecting Pb 2+ . Especially, Nafion-WNCF/BFGCE was successfully applied to determine Pb 2+ in tap water and lake water samples. All the results suggest that the WNCF can be considered as a green and low-cost nanomaterial for the precision detection of Pb 2+ in real samples.
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