Synthesis of mackinawite (FeSm) and its heterogeneous fenton-like catalytic degradation performance of rhodamine B

In this work, Mackinawite (FeSm) was synthesized by the homogeneous precipitation method, which was flower-like nanoparticles formed by the aggregation of nanosheets with a preferred orientation along the (001) plane. The heterogeneous Fenton-like degradation performance of FeSm on Rhodamine B (RhB) was investigated, results illustrated that RhB degradation was the synergistic effect of adsorption, Fenton, and the heterogeneous Fenton-like reaction. In repeated experiments, the reduction of reactivity was attributed to the oxidation of FeSm into lepidocrocite, whereas lepidocrocite has relatively low hydroxyl radicals (•OH) production reactivity. Thus, it showed excellent degradation effects in the long-time degradation of RhB. Photoluminescence (PL) technology and free radical capture experiments demonstrated that •OH produced on the surface of catalyst was the main active species to remove RhB. Meanwhile, the Fe species on the surface of FeSm was the main active center for surface-mediated reactions. The total organic carbon (TOC) test revealed that the degradation was not complete and degradation intermediates were formed. Liquid chromatography-mass spectrometry (LC-MS) technology was used to identify the degradation intermediates. On this basis, possible degradation pathways were proposed.

Development of iron-containing sorption materials for water purification from arsenic compounds

The paper is devoted to the development of a method for obtaining and using iron-containing sorption materials for the effective removal of arsenic compounds of different oxidation states from an aqueous medium. It is known that arsenic compounds have a harmful effect on biota due to high toxicity. The paper theoretically and experimentally substantiates the choice of iron-containing materials as the main sorbent material for arsenic compounds removal from the aqueous medium. A series of iron-containing adsorbents, including powder, activated carbon-based granular and suspension sorbents, was synthesized by different methods (heterogeneous and homogeneous precipitation). Experimental studies have confirmed that the adsorption of arsenate ions on iron-containing sorption materials corresponds to the pseudo-second order of the reaction (R2=0.999), which is inherent in adsorption processes. It was determined that oxyhydroxide sorption materials obtained by the homogeneous precipitation demonstrate higher sorption activity (up to 70 mg/g for As(III) and over 70 mg/g for As(V)). It was found that activated carbon-based iron-containing sorption materials showed approximately 2 times lower efficiency than powder iron(III) oxide, iron(III) oxyhydroxide and amorphous iron(III) hydroxide. It was shown that the use of microfiltration membranes is promising for the removal of spent suspension iron-containing sorption materials. Experimental studies have confirmed that the use of the combination “fine-particle iron(III) oxyhydroxide/membrane” allows removing arsenic compounds from contaminated water to the sanitary requirements level (less than 10 μg As/l) and separating effectively the spent fine-particle sorbent from water

Synthesis of Ni(OH)2, suitable for supercapacitor application, by the cold template homogeneous precipitation method

α-Ni(OH)2 obtained by template homogeneous precipitation exhibits high electrochemical activity in supercapacitors. The main disadvantage is the high energy consumption for maintaining a high temperature during synthesis. To reduce energy consumption, it is proposed to lower the synthesis temperature. In the study, α-Ni(OH)2 was obtained by the method of cold template homogeneous precipitation using Culminal C8465 (0.5 %) as a template for 6 months at t=20–35 °С. The electrochemical characteristics of the sample were studied by cyclic voltammetry and galvanostatic charge-discharge cycling of a pasted binder-free electrode made without introducing an external binder in the supercapacitor mode. It was determined that low-crystalline α-Ni(OH)2 was formed, consisting of agglomerates of spherical particles. Low specific characteristics of nickel hydroxide were revealed at the beginning of cycling due to blocking of the active surface. It was shown that the specific capacity of the sample increased with further cycling due to the breakdown of aggregates into smaller particles; specific capacities of 80 F/g and 38 mA⋅h/g were obtained. However, the lack of binding properties of the template residues was revealed, resulting in a decrease in specific characteristics. It was concluded that it was necessary to introduce an external binder. A previously undescribed effect of a significant increase in the specific capacity during drying of an alkali-impregnated electrode caused by the disintegration of particle agglomerates during alkali carbonization (the maximum capacity is 135 F/g and 69 mA⋅h/g) was revealed. It was concluded that using the revealed effect of any nickel hydroxide samples obtained by various methods of bulk template synthesis was promising