Studies on stabilization effect of calcium dihydrogen phosphate (Ca(H2PO4)2) on Lead(Pb)-contaminated Soil.

This study investigated the effect of Ca(H2PO4)2 on pH, leaching toxicity and speciations of soil before and after leaching on it. Different amounts of Ca(H2PO4)2 were added to Pb-contaminated soil and stabilized for 30 days. The changes of pH and leaching toxicity of Pb-contaminated soil were tracked during that period. The content of Pb in soil before and after leaching was also determined after 30 days of stabilization. Results showed that the pH of the Pb-contaminated soil didn't change much with the addition of-Ca(H2PO4)2. When the amount of Ca(H2PO4)2 reached to 3 wt%, the leaching toxicity met the standard limiting level of groundwater class III of China. The change of leaching toxicity was found to be mainly affected by the water-soluble fraction and mild acid-soluble fraction of lead. The speciation experiments revealed that the changes on reducible, oxidizable, and residual fractions are significant, while there are only minor changes on the water-soluble and mild acid-soluble fractions. X-ray diffractometry (XRD) analysis showed that Pb9(PO4)6 and Pb2P2O7 substances were generated in the stabilized soil. The stabilization mechanism of Ca(H2PO4)2 was mainly attributed to the formation of insoluble Pb phosphate precipitates through interactions between the heavy metal Pb and the Ca(H2PO4)2. In such a way the active species of Pb in the soil can be successfully stabilized. Novelty statementAt present, the leaching toxicity is currently used for the evaluation of stabilization effect of heavy metal contaminated soil. The speciation distribution of stabilized contaminated soil before and after leaching has rarely been studied, and the research on stabilizing contaminated soil after leaching is less.Therefore, this paper mainly studies the stabilization effect through the speciation changes of contaminated soil before and after leaching, providing a new idea and method for the evaluation of the stabilization effect of contaminated soil remediation.Ca(H2PO4)2 has no significance in pH of contaminated soil: 5.05＜pH＜5.5.The content of the water-soluble fraction and the mild acid-soluble fraction of Pb were availably reduced by Ca(H2PO4)2.The content of the water-soluble fraction and the mild acid-soluble fraction of Pb has no marked change before and after leaching.The stabilization mechanism of Ca(H2PO4)2 is through interaction between the Pb in the soil and phosphate to form insoluble substances of lead phosphate.Ca(H2PO4)2 has a good effect on the stabilization of lead-contaminated soil.

Aromatic Ethers Induced Electronic Structure Reconstruction on Encapsulated Nickel Catalysts for High-Performance Catalytic Hydrogenation.

Carbon-encapsulated metal (CEM) catalysts effectively address supported metal catalyst instability by protecting the active metal with a shell. However, mass transfer limitations lead to reduced activity for catalytic hydrogenation reaction over most CEM catalysts. Herein, we introduce a dopant strategy aimed at incorporating nickel metal within graphene-like shells (GLS) featuring oxygen-containing functional groups (OFGs). The core of this strategy involves precise control of GLS modification and the demonstrated pivotal influence of aromatic ether linkages (═C-O-C) in GLS for significant enhancement of catalytic performance. The introduction of ═C-O-C into GLS with stability was beneficial to improve the work function of the catalyst and promoted electron transmission from Ni metal core to GLS, further elevating the catalytic activity, based on the Mott-Schottky effect. In addition, the experimental characterization and density functional theory (DFT) calculations showcased that the ═C-O-C reconstructed the electronic state of GLS, imparting it highly specific for the adsorption of hydrogen and para-chloronitrobenzene (p-CNB) to obtain para-chloroaniline (p-CAN) with high selectivity. This work manifested a feasible direction for the precise modulation and design of the OFGs in CEM catalysts to achieve highly efficient catalytic hydrogenation.

Iron-Based Catalysts with Oxygen Vacancies Obtained by Facile Pyrolysis for Selective Hydrogenation of Nitrobenzene.

The development of preparation strategies for iron-based catalysts with prominent catalytic activity, stability, and cost effectiveness is greatly significant for the field of catalytic hydrogenation but still remains challenging. Herein, a method for the preparation of iron-based catalysts by the simple pyrolysis of organometallic coordination polymers is described. The catalyst Fe@C-2 with sufficient oxygen vacancies obtained in specific coordination environment exhibited superior nitro hydrogenation performance, acid resistance, and reaction stability. Through solvent effect experiments, toxicity experiments, TPSR, and DFT calculations, it was determined that the superior activity of the catalyst was derived from the contribution of sufficient oxygen vacancies to hydrogen activation and the good adsorption ability of FeO on substrate molecules.