Concentration of Thiourea is effective in breaking the dormancy of potato (Solanum tuberosum L.) varieties

Potato germination is highly sensitive to ecological conditions. High altitude and low annual average temperature result in tuber dormancy and poor sprouting. Dormancy has become a significant constraint for lowering potato production, which hinders the possibility of growing two crop cycles per year. An experiment was conducted from February to April 2020. Two major potato varieties (Desiree and Cardinal) were treated with four Thiourea concentrations (0, 1, 2, and 3%) in a two factorial, completely randomized block design with three replications. Tubers were soaked for 2 hours in different Thiourea solution as per treatments, air dried until excess solution was removed and kept in a dark room on plastic trays. With the progress of experiment dormancy breaking and sprouting parameters like early sprouting, dormancy breaking, sprout length and sprout density were recorded. It was found that Thiourea has a significant effect on all observed attributes as per varieties of potato. For Desiree variety, Thiourea (1%) decreased dormancy period by 22 days compared to control (Desiree*Thiourea 0%) and produced the longest average sprout of 7.36cm at 49 days after treatment (DAT). On the other hand, for the Cardinal variety, Thiourea (3%) decreased tuber dormancy by 27 days compared to control (Cardinal*Thiourea 0%) and produced sprout of 7.75 cm at 49 DAT. In case of sprouts/tuber 1% and 3% Thiourea produced 4.13 and 1.91 sprouts/tubers in Desiree and Cardinal, respectively. The overall mean finding indicate that, 1% and 3% Thiourea concentration was significantly superior for breaking dormancy and enhancing sprouting of potato varieties of Desiree and Cardinal respectively.

Obtaining of Nano Gold from Concentrate (Banská Hodruša, Slovakia) Using Algae with Utilization of Mechanochemical Activation

The difficult and predominantly toxic processing of sulphide concentrates with a low gold content has prompted the finding of a more efficient and environmentally friendly method of obtaining this noble metal. This work was therefore focused on the recovery of gold from the concentrate of refractory sulphide complex (Banská Hodruša, Slovakia) using a non-cyanide mechanochemico-biological process. Gold in this complex concentrate is physically located in the intercrystalline space of sulfide minerals and fills in structural defects in sulfides. The precipitation of gold from the complex mineral matrices of the concentrate can be achieved using a mechanochemico-biological process. This innovative process makes it possible to recover gold by applying a thiourea solution, which is a preferred alternative to toxic a cyanidation. The use of a biological process with the application of algae has shown that algae with siliceous structures make it possible to obtain gold from a complex concentrate (Banská Hodruša, Slovakia) with dimensions of the nano. Limnetic algae (diatoms, golden algae) are part of aquatic ecosystems and form the largest of biomass of all plants on Earth. Mechanochemicobiological process is a method that allows to obtain 100 nm gold nanoparticles from refractory sulphide concentrate (Banská Hodruša, Slovakia).

Effect of the Dissolving Method on the Dissolution of Dissolving Pulp Cellulose Fibers with Different Dried-States in Different NaOH/additives Aqueous Solutions

A NaOH/urea (or thiourea) solvent system capable of dissolving cellulose at lower temperatures is a breakthrough in cellulose chemistry, and it was reported that cellulose rapidly dissolved when it was added to a precooled aqueous solution of sodium hydroxide (NaOH) and additives. Therefore, this work compared the effectiveness of the direct dissolution method and freezing-thaw method in dissolving pulp fiber and pure cellulose. Three aqueous solutions were examined: 7% NaOH/12% urea, 9.5% NaOH/4.5% thiourea, and 8% NaOH/8% urea/6.5% thiourea. The dissolving capacity of three NaOH/additives aqueous solutions was analyzed by polarized optical microscopy and the dissolved cellulose proportion was determined. The results showed that the never-dried softwood dissolving pulp and bamboo dissolving pulp achieved better dissolution using freezing-thaw method than using direct dissolution method in the three aqueous solutions. The dissolving method had a negligible effect on the dissolution of each dissolving pulp in the 8% NaOH/8% urea/6.5% thiourea solution. It seems that the direct dissolution method was more suitable for oven-dried microcrystalline cellulose with a low degree of polymerization (DP) and the freezing-thaw method was more suitable for never-dried pulp cellulose fibers with a higher DP.

Uptake and Recovery of Gold from Simulated Hydrometallurgical Liquors by Adsorption on Pine Bark Tannin Resin

The recovery of critical and precious metals from waste electrical and electronic equipment (WEEE) is an environmental and economic imperative. Biosorption has been considered a key technology for the selective extraction of gold from hydrometallurgical liquors obtained in the chemical leaching of e-waste. In this work, the potential of tannin resins prepared from Pinus pinaster bark to sequester and recover gold(III) from hydrochloric acid and aqua regia solutions was assessed. Equilibrium isotherms were experimentally determined and maximum adsorption capacities of 343 ± 38 and 270 ± 19 mg g−1 were found for Au uptake from HCl and HCl/HNO3 (3:1 v/v) solutions containing 1.0 mol L−1 H+. Higher levels of acidity (and chloride ligands) significantly impaired the adsorption of gold from both kinds of leaching solutions, especially in the aqua regia system, in which the adsorbent underperformed. Pseudo-first and pseudo-second order models successfully described the kinetic data. The adsorbent presented high selectivity towards gold. Actually, in simulated aqua regia WEEE liquors, Au(III) was extensively adsorbed, compared to Cu(II), Fe(III), Ni(II), Pd(II), and Zn(II). In three adsorption–desorption cycles, the adsorption capacity of the regenerated adsorbent moderately decreased (19%), although the gold elution in acidic thiourea solution had been quite limited. Future research is needed to examine more closely the elution of gold from the exhausted adsorbents. The results obtained in this work show good perspectives as regards the application of pine bark tannin resins for the selective extraction of Au from electronic waste leach liquors.

Bio-Oxidation of a Double Refractory Gold Ore and Investigation of Preg-Robbing of Gold from Thiourea Solution

Carbonaceous sulfidic gold ores are commonly double refractory and thus require pretreatment before gold extraction. In this paper, the capacity of pre-bio-oxidation can simultaneously decompose sulfides or deactivate carbonaceous matters (CM) from a double refractory gold ore (DRGO) using pure cultures of A. ferrooxidans or L. ferrooxidans, and a mixed culture containing A. ferrooxidans and L. ferrooxidans was investigated. The results showed that direct thiourea leaching of the as-received DRGO yielded only 28.7% gold extraction, which was due to the encapsulation of sulfides on gold and the gold adsorption of CM. After bio-oxidation, thiourea leaching of the DRGO resulted in gold extraction of over 75–80%. Moreover, bio-oxidation can effectively reduce the adsorption of carbon to gold. XRD, SEM-EDS and FTIR analysis showed that many oxygen-containing groups were introduced on the surface of DRGO during bio-oxidation, while the C=C bond was cleaved and the O–C–O and C–N bonds were degraded, causing a decrease in active sites for gold adsorption. Moreover, passivation materials such as jarosite were formed on the surface of DRGO, which might reduce the affinity of CM for gold in solutions. In addition, the cleavage of the S–S band indicated that sulfides were oxidized by bacteria. This work allows us to explain the applicability of pre-bio-oxidation for degrading both sulfides and CM and increasing gold recovery from DRGO in the thiourea system.

Controlled Growth of BiSI Nanorod-Based Films through a Two-Step Solution Process for Solar Cell Applications

Pb-based hybrid perovskite solar cells, despite their advantages, face challenges in commercialization. In recent years, Bi-based chalcohalides are being considered as potential alternative candidates, however, their current device efficiency remains unsatisfactory. Herein, a two-step solution method is developed and applied to the fabrication of BiSI films. The method consists of the formation of Bi2S3 (step I) and its conversion to BiSI (step II). The Bi2S3 was fabricated by a thiol-amine solution process and the BiSI conversion was achieved by chemical reaction between the as-formed Bi2S3 and BiI3. It was found that the formation of BiSI was highly dependent on the Bi:S molar ratio of the Bi2O3-thiourea solution and the number of times of step I. The as-fabricated BiSI film had an optical band gap of 1.61 eV and exhibited nanorod morphology. In addition, the electronic structure is explored and discussed for solar cells applications.

Effect of pre-germinative treatments on Nothofagus glauca seed germination and seedling growth

Background: Nothofagus glauca (Phil.) Krasser (Nothofagaceae, “Hualo”) is an endemic tree of the Mediterranean zone of Chile. The natural forests in this area have been severely fragmented as a result of human causes such as replacement by agricultural crops and fast-growing tree species. From 1975, these forests have declined from 900,000 ha to 145,000 ha, so it is categorised on the IUCN Red List as ‘vulnerable’. In restoring this ecosystem, efforts should focus, in part, on the propagation of quality stock. However, information on propagation systems is still insufficient. Methods: We aimed to analyse the effect of different pre-germinative treatments and sowing times on seed germination, and seedling growth and quality. The pre-germinative treatments were: (i) cold stratification; (ii) soaking in gibberellic acid (GA3) and thiourea solution; and (iii) nursery cultivation, while the sowing times were July, August and September. Results: A high germination capacity was achieved by: soaking the seeds in GA3 solution irrespective of concentration; stratifying, irrespective of period; or soaking in 7.5 mg L-1 thiourea solution, values significantly varied from that of the control treatments. The sowing time was not relevant in terms of the percentage of germination or seedling development. Stratification at 5°C for 60 days produced the best quality indices for N. glauca seedlings but no significant differences were found in any of the morphological attributes tested as a result of the pre-germinative treatments. Conclusions: The pre-germinative treatments significantly improved the germination and seedlings growth of N. glauca. Cold stratification at 5°C for 60 days is recommended as it produced suitable seedlings for field establishment. Gibberellic acid and thiourea did not produce important effects on seedling growth. Our results suggest the presence of endogenous physiological dormancy of the N. glauca seeds. The results of this study provide important information on propagation and nursery techniques of N. glauca, which can be used in restoration programmes.