Synergistic effect of p-type and n-type dopants in semiconductors for efficient electrocatalytic water splitting

The main challenge for acidic water electrolysis is the lack of active and stable oxygen evolution catalysts based on abundant materials, which are globally scalable. Iridium oxide is the only material, which is active and stable. However, Ir is extremely rare and far from scalable. There exist both active materials and stable materials, but those that are active are not stable and vice versa. In this work, we present a strategy for making stable materials active. The stable materials are semiconductors that cannot change oxidation state at relevant reaction conditions. Based on DFT calculations, we find that by adding an n-type dopant, semiconductor surfaces can bind oxygen. However, after oxygen is adsorbed, the material is again in a state where it cannot bind or desorb oxygen. By combining n-type and p-type dopants, the reactivity can be tuned so that oxygen can be adsorbed and desorbed under reaction conditions. It turns out that the tuning can be understood from the electrostatic interactions between the dopants as well as between the dopants and the binding site. We experimentally verify that this strategy works in TiO2 by co-doping with different pairs of n- and p-type dopants. This encourages that the co-doping approach can be used to activate stable materials, without intrinsic oxygen evolution activity, to discover new catalysts for acid water electrolysis.

Volume change in compacted claystone-bentonite mixtures as affected by the swamp acidic water

Water containing sulfuric acid with a pH up to 3 is prevalent in swampy areas. This article focuses on the effects of the solution on volume change of compacted claystone?bentonite mixture. Claystone was obtained from Banjarbakula landfill and it was mixed with bentonite on a 5, 10, 15, and 20% dry mass basis. Samples possessed the dry density of 16 kN/m3 and moisture content of 10, 15, and 20%. The odometer examined the samples' swelling and compression in both pure and acidic water. Characterization tests i.e., XRF, XRD, and FTIR were also performed. The results showed that swelling and compression were affected by initial moisture and bentonite content. Samples with a moisture content of 20% showed compression in acidic water. Acidic water changed the water absorbed on the clay surface without altering the mineral. A mixture containing 20% bentonite compacted to optimum moisture content was found at best in reducing the acidic water effects.

The neutralizing of Acidic Wastewater Produced From Trinitrotoluene (TNT) Factory by Rock granules

Acidic wastewater treatment for the TNT factory which located in the middle of the mountains is characterized by part of its nature with alkaline properties, which prompted the researcher to take advantage of it in the treatment of acidic water instead of caustic soda. Acidic waste water is originated from spent acid treatment building, nitration, purification building, drying and packing building in TNT factory. The objective of this study is to use treated Acidic water TNT Factory by rock granules. Acidic waste water is mixed together with rock granules lye after crushed process of these rocks. The results the pH value of water after neutralizing reaction showed a significant rise in pH from 1.20 to 7. 00. This is within the SSMO. These data included reduction in BOD from 30.00 to 7.00 mg/l which is also within the range of SSMO. The COD value of the acidic wastewater which is 65.00 mg/l to 11 mg/l which is also within the range of SSMO. The use of rock granules for treatment will save an amount 9.45kg/t of caustic soda per ton of product TNT product.

Comparison of Different Extraction Solvents for Characterization of Antioxidant Potential and Polyphenolic Composition in Boletus edulis and Cantharellus cibarius Mushrooms from Romania

Edible mushrooms are well-known for their nutritional benefits and low energy density. In addition, mushroom extracts contain various bioactive compounds that account for their antioxidant activity; the applied extraction conditions influence the extraction efficiency of such compounds. Therefore, this study investigates the effects of four extractants on the content of polyphenols and antioxidant properties of Boletus edulis and Cantharellus cibarius mushrooms, aiming to optimize the extraction process. Powders of B. edulis and C. cibarius mushrooms were subjected to extraction with acidic water (10% CH3COOH), ethanol/water/acetic acid (15:76.5:8.5, v/v/v), hexane, and diethyl ether to measure their total phenolic content (TPC), total flavonoid content (TFC), and Trolox equivalent antioxidant capacity (TEAC). Furthermore, the level of individual polyphenolic compounds in these extracts was quantified using an HPLC-DAD-ESI-MS method. Results showed that the type of solvent significantly influenced the TPC and TEAC of mushroom powder but insignificantly influenced the TFC. A very strong positive correlation was found between TPC and TEAC, but no correlation was found between TFC and TEAC or TPC and TFC. Acidic water extracted the highest amount of polyphenolic compounds from these mushroom powders. Therefore, the aqueous extract showed the highest TPC and strongest antioxidant activity. Thus, acidic water is recommended for polyphenol analysis in B. edulis and C. cibarius mushrooms.

Small-scale field evaluation of geochemical blending of waste rock to mitigate acid rock drainage potential

Blending of potentially acid generating (PAG) waste rock with non-PAG waste rock to create a rock mixture which performs as non-PAG is a possible approach to permanent prevention of acid rock drainage (ARD) for PAG waste rock. In 2012, a field weathering study using 300 kg samples was implemented at Teck Coal's Quintette Project located in northeastern British Columbia, Canada to test the prevention of acid generation in the PAG waste rock by dissolved carbonate leached from overlying non-PAG waste rock and direct neutralization of acidic water from PAG waste rock by contact with non-PAG waste rock.After eight years of monitoring the experiments, the layered non-PAG on PAG barrels provided proof-of-concept that as the thickness of the PAG layer increases relative to the thickness of the non-PAG layers, acidic waters are more likely to be produced. The PAG on non-PAG layering has resulted in non-acidic water and no indications of metal leaching despite accelerated oxidation in the PAG layer shown by sulphate loadings. The study has demonstrated that the scale of heterogeneity of PAG and non-PAG materials is a critical consideration for providing certainty that rock blends designed to be non-PAG will perform as non-PAG in perpetuity. This is contrary to the standard paradigm in which an excess of acid-consuming minerals is often considered sufficient alone to ensure ARD is not produced.

A new minute riffle beetle (Coleoptera: Elmidae: Pagelmis) from the Brazilian Amazon

The monotypic genus Pagelmis Spangler, 1981 was described from six thousand specimens of Pagelmis amazonica Spangler, 1981 collected with blacklight traps in Ecuador. For many years the known distribution of this genus was restricted to its type-locality, and recently it was recorded in Venezuela, Suriname and Brazil (Roraima State). Now, 40 years after the description of the genus, we describe the second Pagelmis species, based on male and female collected in the Amazon forest (Amazonas State, Brazil). With the description of the second species in the genus we provide an emended diagnosis of Pagelmis. Since adults of this genus were previously collected only in light traps, no habitat information was known. We collected adults of the new species in the first- and second-order streams with black, acidic water and sandy streambeds. The main substrates available in these streams were leaves and roots of riparian vegetation.