Removal of Hg(II) from aqueous solution using sodium humate as heavy metal capturing agent

Novel pyridine-based covalent organic framework containing N,N,N-chelating sites for selective detection and effective removal of nickel

A novel pyridine-based COF material with functional N,N,N chelating sites has been designed and synthesized, which has the dual functions of fluorescence detection and efficient removal of Ni2+ from aqueous solution.

Thiolated Polyethyleneimine-Based Polymer Sponge for Selective Removal of Hg2+ from Aqueous Solution

Polymer sponges with molecular recognition provide a facile approach to water purification and industrial separation with easy operation. Herein, a thiolated polyethyleneimine (PEI)-based polymer sponge was prepared through cryo-polymerization of PEI, followed by grafting of PEI and then post-modification of the amine functionalities present within the hyperbranched structure with methyl mercaptoacetate, which afford high density of thiol functional groups on the surface of the sponge. The developed sponge was characterized by scanning electron microscopy and element analysis, and the adsorption kinetic and isotherm studies were conducted in detail. The sponge presents a remarkable maximum adsorption capacity of 2899.7 mg/g, which can be attributed to its high density of thiol functionalities. The sponge also shows excellent selectivity toward Hg²⁺ against other metal ions and natural organic matter, indicating its great potential in removing mercury from real water bodies. In addition, the sponge can be chemically regenerated and exhibits good reusability, which decreases the economic and environmental impacts. Hence, the high removal efficiency, high selectivity toward mercury, and good reusability of the sponge material highlight it as a promising sorbent for mercury removal in water pollution treatment.

Reactivity Improvement of Ca-Based CO2 Absorbent Modified with Sodium Humate in Cyclic Calcination/Carbonation

The Ca-based sorbent cyclic calcination/carbonation reaction (CCCR) is a high-efficiency technique for capturing CO₂ from combustion processes. The CO₂ capture ability of CaO modified with sodium humate (HA-Na) (HA-Na/CaO) in long-term calcination/carbonation cycles was investigated. The enhancement mechanism of HA-Na on CCCR was proposed and demonstrated. The effects of carbonation temperature, reaction duration, and the addition amount of HA-Na on the carbonation rate of the CaO adsorbent were also studied. HA-Na/CaO is allowed to react 20 min at the optimum conditions for calcination (920 °C, 100% N₂) and for carbonation (700 °C, 15% CO₂, 85% N₂), respectively. HA-Na plays a key role in the CCCR process, and the carbonation conversion rate is lifted obviously. The maximum conversion rate of HA-Na/CaO is 23% higher than that of CaO in the first cycle. After 20 cycles, the conversion rate of HA-Na/CaO is still 0.28, while that of CaO is only 0.15. The carbonation conversion rate for HA-Na/CaO is improved by 86% compared to CaO. In addition, the characteristics of calcined sorbents are analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) methods.

Effect of nitric acid pre-oxidation concentration on pore structure and nitrogen/oxygen active decoration sites of ethylenediamine -modified biochar for mercury(II) adsorption and the possible mechanism

Controlling of pre-oxidation conditions can effectively enhance the aimed active functional groups via promoting the oxidation and grafting reaction on biochar's surface. Here, the effect of different nitric acid pre-oxidation concentration (NAPOC) was investigated on the type and content of active oxygen-containing functional sites during the pre-oxidation stage, as well as the active nitrogen-containing binding sites for the following grafting process. And the possible reaction mechanisms for introducing nitrogen/oxygen-containing functional groups such as amide, pyridinic, carbonyl, carboxyl, etc., into the surface by ethylenediamine (EDA) were proposed. The samples were characterized by various analyses including N₂ adsorption/desorption, Boehm titration, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Results showed that the NAPOC played a crucial role in promoting the formation of oxygen-containing initiators, and difference of NAPOC resulted in different reaction principles. At higher NAPOC, more carbonyl, carboxyl and hydroxyl functional groups were formed, which facilitated the decoration of nitrogen binding active sites of amide and pyridinic for mercury ions adsorption into the carbon lattice of mesoporous biomass-derived biochar (MBB). The proportions of micropore and mesopore remained basically unchanged, indicating that the decorated nitrogen/oxygen sites were highly uniformly dispersed in MBB's frame and thus resulted in high activity. The comparison of adsorption properties of MBB showed that MBB-25-EDA had the highest adsorption capacity of 153 mg g^-1 at pH 6, confirming that the 25% was the optimum NAPOC for introducing nitrogen/oxygen functional binding sites for effectively anchoring mercury.