Silica monolayer isolation of electrodeposited SERS substrate and online probing of molecule adsorption onto mineral microparticles in relation to flotation.

In the minerals processing industry, the surface chemistry of mineral particles and its real-time detection can significantly enhance process performance, and ultimately leading to automotive and intelligent control. The adsorption of collector molecule onto bulk mineral specimens could be investigated with the help of shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS). However, this method is unsuitable for the online detection of particles fluid consisted of micro-sized chalcocite that encountered in industrial production processes. In this work, a novel strategy of shell-isolated nanoparticles synthesis by electrodeposition of gold nanoparticles film and isolation of this film with crosslinked silica monolayer was proposed. The adsorption of 2-mercaptobenzothiazole (MBT), a typical flotation collector, onto a copper sulfide mineral, chalcocite was measured in-situ with the help of such a SERS substrate. Enhancement factors of 106-107 was calculated based on an idealized model. Furthermore, we discussed the stability of the silica isolation monolayer under high-power laser irradiation.

Effect of chitosan on the mechanical properties and acid resistance of metakaolin-blast furnance slag-based geopolymers.

Adding organics in the process of geopolymer synthesis can combine the functional groups of organics with the three-dimensional structure of geopolymer, thus changing the properties of geopolymer such as compressive strength, flexural strength, and acid resistance. In this work, excellent mechanical properties and acid resistance of metakaolin-blast furnance slag (Mk-BFS)-based geopolymer were synthesized by the incorporation of chitosan. The formation of sodium-alumino-silicate-hydrate (N-A-S-H) gel and calium-alumino-silicate-hydrate (C-A-S-H) gel in geopolymerization were characterized by 29Si nuclear magnetic resonance (NMR). At 5% of chitosan, the compressive strength of Mk-BFS-based geopolymer could reach to 33.7 MPa. The results could be ascribed to that chitosan reacts with geopolymer to generate new C-O-Si structure meanwhile adhesion produced by the combination of positively charged cations and negatively charged ions makes the structure of geopolymer denser. After 7 days of sulfuric acid immersion, the reduction of compressive strength is less than 3 MPa, demonstrating its great acid resistance. The acid resistance of Mk-BFS-based geopolymer could attribute to that the free amino groups in chitosan preferentially react with acid solution and weakened the erosion of sulfuric acid. This study optimizes the compressive strength and acid resistance of geopolymer by adding appropriate amount of chitosan.

Simultaneous separation of Fe & Al and extraction of Fe from waste coal fly ash: Altering the charge sequence of ions by electrolysis.

A significant amount of coal fly ash is generated and this type of waste material causes severe environmental hazards. Metal (Al and Fe) extraction from coal fly ash is beneficial to the resource utilization of waste coal fly ash. However, the coexistence of Al and Fe in coal fly ash means that the separation of Al and Fe is required, which is a key and difficult step to prepare high value-added products from coal fly ash. This work presents a novel electrolysis method to alter the charge sequence of Al3+, Fe3+, and H2O, leading to a process different from their natural tendency for simultaneous separation of Fe3+ and Al3+, and extraction of Fe. The single iron removal efficiency was 43.48%, and the aluminum extraction efficiency was <0.30% under optimal conditions. The iron product had a purity of 98.3 wt% Fe, 0.45 wt% Al, and 0.18 wt% S. This process occurs without chemical additions and expensive membranes, avoiding impurity introduction, slag generation, and membrane limitations. Fe(s), H2(g), Al2(SO4)3(aq), and O2(g) are the main products during the electrolysis. Flake Fe is selectively produced instead of colloidal Fe(OH)3. Fe is a magnetic substance and is easier to remove from the solution by magnets than colloidal Fe(OH)3. H2 is a green fuel. Wastewater (Al2(SO4)3(aq)) can be directly used to further extract alumina. Therefore, this study provides an alternative method of zero pollution discharge for simultaneous separation of Fe3+ and Al3+, and extraction of Fe from coal fly ash leachate.

Clean production of porous-Al(OH)3 from fly ash.

Fly ash is one of the largest solid waste and causes serious environment problems. Extraction of Al(OH)3 from fly ash is beneficial to environment and economy. We developed a clean electrolysis method to generate hydroxyl groups in situ to extract Al(OH)3 from fly ash leachate without adding chemicals or using expensive membranes, avoiding the introduction of new impurities, secondary pollutants generation, and membrane limitations. Batch experiments yielded porous electrolytic products with BET surface areas from 11.7610 to 25.5267 m2/g, pore volumes from 0.1935 to 0.1643 cm3/g and pore sizes from 65.7960 to 25.7434 nm. The composition of the electrolytic products was 86.43 wt% Al(OH)3, 9.00 wt% SO3, 1.67 wt% Fe(OH)3, and 0.29 wt% Ca(OH)2. The current efficiency was 90.51 % under optimized conditions of c (Al3+) = 0.1 M, t =2 h, and J = 750 A/m2. Mean particle size was from 24.1-98.1 µm. Impurities mainly affected the composition of the electrolytic products. The OH- generated by H2O reduction reacted with Al3+, Fe3+, and Ca2+ to generate a hydroxide. Fe3+ preceded Ca2+ into the hydroxide. H2 released continuously from H2O reduction, resulting in a porous hydroxide. The wastewater was reused as a leaching reagent to promote zero-pollution discharge.

Current Status and Challenges of Methyltrimethyltridecylchromans Research in Source Rocks and Crude Oils.

Methyltrimethyltridecylchromans (MTTCs) are structurally similar to tocopherols, which were identified in large numbers of source rocks and crude oils (Pleistocene to Early Cambrian). The occurrence of MTTCs was widely used as a proxy indicator of paleosalinity in the field of organic geochemistry. However, their origin and geological formation pathway still remain greatly debated. Here, we review the progress made over the past 30 years in the distribution and origin of MTTCs and their applications. Furthermore, we discussed several key points for future studies on MTTCs.