Distribution and modes of occurrence of uranium in coals of Eastern Yunnan, China

Uranium is an environmentally hazardous element, and is commonly present at trace levels (2.4 μg/g for world coals) in coal deposits. However, selected coal deposits could be highly enriched in uranium. In this study, 15 coal samples were collected from Eastern Yunnan coal deposits, China, aiming to characterize the distribution and the occurrence of uranium in those coals. In studied samples, uranium content varied from 0.36 to 8.28 μg/g, with an average value of 3.76 μg/g. Generally, uranium content in coals from northern coal mines (3.02 ± 2.44 μg/g, n = 5) were lower than it in southern coal mines (4.13 ± 2.30 μg/g, n = 10). Uranium in coal samples showed no obvious correlation with total sulfur, whereas was positively correlated with ash yield. The results of sequential chemical extraction procedure confirm that organic-bound is the dominant occurrence of uranium. The slight enrichment of uranium in studied coals was probably attributed to sedimentation processes, hydrological conditions and tectonic structure of the coal deposits.

Adsorption of Mercury Using Different Types of Activated Bentonite: A Study of Sorption, Kinetics, and Isotherm Models

Mercury is a hazardous element because of its toxicity and harmful effects on human health. Various traditional and low-cost methods have been developed to remove mercury from wastewater. This study used local raw material as an alternative adsorbent to treat mercury-contaminated wastewater. Activated bentonite was prepared using different chemical activators (H3PO4, HCl, and ZnCl2) in various concentrations. Then, it was dried at 200°C for an hour. The materials were characterized by SEM-EDS. Its percent removal and isotherm models were analyzed. In this study, the most effective activator was H3PO4 and the experimental data matched the Freundlich model.

The Use of High-Alloyed EAF Slag for the Neutralization of On-Site Produced Acidic Wastewater: The First Step Towards a Zero-Waste Stainless-Steel Production Process

Recycling of steelmaking slags has well-established applications, such as their use in cement, asphalt, or fertilizer industries. Although in some cases, such as the electric arc furnace (EAF) high-alloyed stainless-steel production, the slag’s high metal content prevents its use in such applications. This forces companies to accumulate it as waste. Using concepts such dematerialization, waste management, industrial symbiosis, and circular economy, the article drafts a conceptual framework on the best route to solving the landfilling issue, aiming at a zero-waste process re-design. An experimental part follows, with an investigation of the use of landfill slag as a substitute of limestone for the neutralization of acidic wastewater, produced by the rinsing of steel after the pickling process. Neutralization of acidic wastewater with both lime and slag samples was performed with two different methods. Two out of four slag samples tested proved their possible use, reaching desired pH values compared to lime neutralizations. Moreover, the clean waters resulting from the neutralizations with the use of both lime and slag were tested. In terms of hazardous element concentrations, neutralization with slag yielded similar results to lime. The results of these trials show that slag is a potential substitute of lime for the neutralization of acidic wastewater.

Facilitated Chromium(VI) Transport across an Ionic Liquid Membrane Impregnated with Cyphos IL102

Chromium(VI) is a well-known hazardous element, thus, its removal from aqueous sources is of a general concern. Among the technologies used for the removal of this type of toxic elements, liquid membranes are gaining in importance and the same has occurred with the use of ionic liquids, considered for many, due to their properties, as green solvents. Thus, the present work joined the three previous points, presenting an experimental study about the removal of chromium(VI) by the use of a liquid membrane operation which used the commercially available Cyphos IL102 ionic liquid as a carrier. The experimental variables included: the stirring speed applied to the feed and receiving solution (a key-parameter to gain maximum transport), acid, chromium(VI), sodium hydroxide and Cyphos IL102 concentrations in their various phases. Additionally, the performance of the present system was evaluated both against the presence of other metals in solution and other carriers. The experimental results confirmed that Cyphos IL102 is a good carrier for chromium(VI) transport and, thus, its removal from aqueous streams, and it also performed well in the presence of accompanying metals and against the performance of other commercially available carriers.