Black locust (Robinia pseudoacacia) is recognised as a forest species of interest due to its multiple uses. The management of forest genetic resources and their efficient conservation suffer from variations in traits and start with seed germination. The aim of the current study was to investigate the germination of seeds obtained from plus trees selected in eight Romanian provenances, as well as to investigate the influence of the origin upon plants’ growth and development. Two experiments were undertaken to test seed germination: one treatment involved water-soaked seeds and heat/cold treatment, while the other treatment was based on sulphuric acid, at different concentrations (50, 70, 90%). The results were correlated with the morphological analysis of the seeds. Satu-Mare had the lowest germination rate within both treatments. Sulphuric acid did not improve seed germination as much as the heat treatment. The highest germination rate occurred for the water and temperature treatment on seeds from Bihor provenance (68.2%). The most distant provenance was Bihor, in inverse correlation with Bistrița Năsăud and grouped separately within the hierarchical dendrogram of cluster analysis based on the analysed parameters of the provenances investigated. The results demonstrated that the genotypes and environmental heterogeneity of the seed origin within the provenances may finally result in different performances.
Nowadays, an alkali-activated binder has become an emergent sustainable construction material as an alternative to traditional cement and geopolymer binders. However, high drying shrinkage and low durability performance in aggressive environments such as sulphuric acid and sulphate are the main problems of alkali-activated paste, mortar and concrete. Based on these factors, alkali-activated mortar (AAM) binders incorporating high-volume palm oil fuel ash (POFA), ground blast furnace slag (GBFS) and fly ash (FA) were designed to enhance their durability performance against aggressive environments. The compressive strength, drying shrinkage, loss in strength and weight, as well as the microstructures of these AAMs were evaluated after exposure to acid and sulphate solutions. Mortars made with a high volume of POFA showed an improved durability performance with reduced drying shrinkage compared to the control sample. Regarding the resistance against aggressive environments, AAMs with POFA content increasing from 0 to 70% showed a reduced loss in strength from 35 to 9% when subjected to an acid attack, respectively. Additionally, the results indicated that high-volume POFA binders with an increasing FA content as a GBFS replacement could improve the performance of the proposed mortars in terms of durability. It is asserted that POFA can significantly contribute to the cement-free industry, thus mitigating environmental problems such as carbon dioxide emission and landfill risks. Furthermore, the use of POFA can increase the lifespan of construction materials through a reduction in the deterioration resulting from shrinkage problems and aggressive environment attacks.
Olive stones are a by-product of the olive oil industry. In this work, the valorisation of olive stones through pyrolysis was attempted. Before pyrolysis, half of the samples were impregnated with sulphuric acid. Pyrolysis was carried out in a vertical tubular furnace with a ceramic support. The pyrolysis conditions assayed were: temperature between 400 and 600 °C, heating ramp between 5 and 20 °C∙min−1, and inert gas flow rate between 50 and 300 mL Ar∙min−1. Among them, temperature was the only parameter that influenced the pyrolysis product distribution. The most suitable temperature for obtaining biochar was 400 °C for both non-treated and pre-treated raw material, while for obtaining bio-oil, it was 600 °C for impregnated olive stones and 400 °C for the raw material. The impregnated olives stones led to bio-oils with much higher amounts of high-added-value products such as levoglucosenone and catechol. Finally, the biochars were impregnated with sulphuric acid and assayed as biocatalysts for the esterification of oleic acid with methanol in a stirred tank batch reactor at 60 °C for 30 min. Biochars from non-treated olive stones, which had lower specific surfaces, led to higher esterification yields (up to 96.2%).
This study examined the corrosion inhibiting properties of parsley (petroselinum sativum) essential oils, for Type 430 ferritic stainless steel in 0.5 molar sulphuric acid solutions. In this study, weight loss, electrochemical and scanning electron microscope techniques were used in gaining a detailed understanding of inhibition effects of parsley (petroselinum sativum) essential oils (PEO) on Type 430 ferritic stainless steel corrosion. The inhibitor studied exhibits good anti-corrosion performance with 98.65 % inhibition efficiency. This result could be ascribed to the adsorbed PEO on the surface of the stainless steel, and this was verified by surface visualization using optical and scanning electron microscope techniques while the crystallographic variation of the inhibited sample is studied by X-ray diffraction (XRD). The adsorption of PEO onto stainless steel surface is controlled by Langmuir adsorption isotherms. Optical images of non-inhibited specimens showed a severely corroded surface with a visible macro pit on the stainless steel from sulphuric solutions. The inhibited sample shows improved surface owing to the surface protection effect of PEO molecules. The corrosion inhibition performance of PEO is due to the presence of active constituents which enhanced the film formation over the surface of the metal, thus, mitigating corrosion.
The present paper gives the thus far unpublished results of a pilot-scale heap leaching test of a Greek low-grade nickel oxide ore, aiming at verifying, at a large scale, the amenability of Greek laterites to heap leaching by the HELLAS (Heap Leaching LAteriteS) process, developed at the National Technical University of Athens for the first time worldwide and patented by some of the authors as early as in 1991. The test was conducted at the site of Aghios Ioannis mine of G.M.M.S.A. LARCO in 2006–2008 and was financed and supervised by the Institute of Geology and Mineral Exploration (I.G.M.E). The ore sample, 800 t, was from the “Triada” deposit of LARCO, in Euboea, and contained 0.73% nickel, 0.06% cobalt, 35.6% iron and 15% silicon. The ore was ground to −18 mm and the leaching agent was 2N (100 g/L) sulphuric acid solution. The nickel and cobalt recoveries obtained at the time of termination but not completion of the test, after four leaching cycles and 114 days of irrigation, were 60 and 36%, respectively. The corresponding nickel and cobalt concentrations in the produced leach liquor were 3.4 and 0.17 g/L, respectively. The value of the ratio Fe/Ni in the leach liquor was 10/1, much lower than the value 45/1 in the ore, thus showing the selectivity of the leaching of nickel over iron in the Greek ores by the above method. The consumption of sulphuric acid was 66 kg H2SO4/kg Ni recovered. The preliminary feasibility study, that followed the test, confirmed the economic viability of the integrated HELLAS process for the low-grade nickel oxide ores of Greece.
Rice straw, an abundant agricultural waste, possesses immense potential to serve as renewable, eco-friendly and non-edible feedstock to generate value-added products. Therefore, the present study aimed to obtain prebiotic neutral xylooligosaccharides (XOS)-rich autohydrolysate from rice straw xylan. The central composite design of response surface methodology was employed to optimize the conditions for the alkaline extraction of xylan, i.e. NaOH concentration (6-14%, w/v), reaction time (1-3.5 h) and temperature (50-100 °C). Autohydrolysis of xylan was carried out at 121 °C and 15 psi for varied hydrolysis times (10, 25 and 40 min) and sulphuric acid concentrations (0.1, 0.5 and 1.0M) to obtain XOS-rich autohydrolysate. The optimum conditions were found to be as follows: 11.04% (w/v) NaOH, 3.126 h and 80.146 °C, so that the maximum xylan yield of 19.97% was predicted by the software. This value was quite close to the experimental yield of 19.4%, with 80.83% xylan being recovered per gram of rice straw. The best autohydrolysis treatment for xylan was found to be using 0.1M sulphuric acid for 10 min, which allowed 34.5% of 100 mg xylan to be depolymerized to produce neutral XOS (degree of polymerization up to 7), with xylose, xylobiose and xylotriose constituting 4.45, 10.14 and 7.83 mg, respectively. These autohydrolysates promoted higher growth of Lactobacillus rhamnosus and Lactobacillus casei than established prebiotic fructooligosaccharides. The study attempts to solve disposal issues of rice straw through production of XOS-rich autohydrolysates in demand on the global nutraceuticals market.