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Thermodynamic and Kinetic Analysis of Cobaltite Oxidation Process
No full textIn this paper results of the thermodynamic and kinetic analysis of cobaltite oxidation process were presented. Inductively coupled
plasma atomic emission spectroscopy (IC P-AE S) and energy dispersive X-ray fluorescence (ED-XRF) were used to determine
the chemical composition of the examined cobaltite. The results of the chemical analysis showed that the tested sample of cobaltite
mainly consists of cobalt, sulfur, calcium, arsenic, and iron, with a trace amount of some other elements. Also, some analyses were
obtained by X-ray diffractometry (XRD) and scanning electron microscopy (SEM) coupled with energy dispersive spectrometry
(EDS). Mineralogical analysis by X-ray diffractometry shows the existence of four phases: the minerals cobaltite, calcite, pyrite,
and jaipurite. Based on the calculated phase stability diagram of the Co-S-O and As-S-O systems, a thermodynamic analysis of the
cobaltite oxidation process was performed. The results of thermogravimetric analysis and differential thermal analysis (TG/DTG)
were used to determine the mechanism of the oxidation process. Using the Sharpe method of reduced reaction half-time, a kinetic
analysis was performed under isothermal conditions in the temperature range from 300°C to 900°C. The calculated value of the
activation energy of the oxidation process is 8.3 kJ/mol–1
Structural and morphological properties of Y-TiO2
No full textWater pollution by organic matters is in increase. Photocatalytic degradation of various
pollutants presented in environment has promising future. Different materials have been
applied in previous scientific works, while TiO2 based materials posse’s great physicochemical
characteristics. Therefore, researchers are constantly developing various
heterostructures with advanced properties with aim to readily degrade present pollution. In
this paper, our goals were to investigate structural and morphological properties of novely
synthesized Y-TiO2 photocatalyst. With those purposes, several tests were done, like
Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS),
structural stability (SS) etc. Results show that obtained material has prominent
photocatalytic activity in five consecutive cycles
Zeolite Acid (Un)Stability as Major Disadvantage for Its Human Consumption
No full textThis study was conducted to examine the potential harmful effects of zeolite consumption in daily
supplementation. The research focused on the acid stability of zeolite in HCl solution at pH values ranging from
1.5 to 3, corresponding to gastric pH levels. The initial zeolite sample, as well as the samples subjected to acidic
treatment, were characterized using X-ray diffraction (XRD) method, and their chemical composition was
analyzed. The results obtained indicate that the crystalline structure of zeolite was not disrupted during the
treatment. At a pH of 1.5, up to 2% of aluminum leached into the solution, while at higher pH values, no
aluminum leaching was observed. These findings underscore the need for cautious consideration of zeolite
supplementation due to potential aluminum release in highly acidic environments
Advanced sulfur-polymer composites for sustainable construction: Optimized production and structural performance under acidic exposure
No full textThis study investigates the optimized production and structural performance of sulfur-polymer composites for sustainable construction, particularly under acidic exposure. Addressing a current knowledge gap in the long-term behavior of these materials, the research focuses on microstructural transformations and their effect on homogeneity during chemical impact. The work introduces a novel synthesis method, involving a modified sulfur binder created through simultaneous heating of sulfur and pre-modified sulfur, which enhances structural stability and material uniformity. Composites were subjected to artificial aging in a 10 % hydrochloric acid solution to simulate aggressive environmental conditions. Advanced techniques, including mathematical morphology, SEM, ultrasound wave analysis, and mechanical testing, were applied to monitor structural changes. Results demonstrated significant sulfur redistribution within the composite, leading to increased homogeneity and improved resistance to chemical degradation. Ultrasound analysis revealed peak structural homogeneity after 21 days of exposure, attributed to sulfur's secondary bonding and compaction effects. Mechanical testing confirmed the composite's stability, with no significant loss in strength. These findings provide new insights into both the synthesis and durability of sulfur-polymer composites, supporting their application as high-performance, sustainable materials in chemically aggressive environments
Efficient Adsorption of Lead on Hydro-Pyrochar Synthesized by Two-Step Conversion of Corn Cob in Magnesium Chloride Medium
No full textThis study used widely available waste biomass, corn cob (CC), to remove Pb ions
from aqueous solutions. A two-step conversion of this material was carried out to improve
its adsorption characteristics. Firstly, CC was prepared by hydrothermal carbonization;
afterward, the obtained hydrochar was doped by MgCl2 and pyrolyzed. The synthesized
hydro-pyrochar (HCC-Mg) was used for adsorption experiments in a batch system. The
surface and structural properties of HCC-Mg were characterized by SEM-EDX and FTIR
analysis before and after Pb adsorption. Kinetic and isotherm models were applied to the
experimental results. It was confirmed that Pb adsorption on HCC-Mg occurred rapidly,
with a maximum adsorption capacity of 87.08 mg/g. The pseudo-second-order model best
described the adsorption process, while the best fit of the experimental data was observed
with the Sips isotherm model. The results of this study showed that the capacity of the
synthesized HCC-Mg material had increased more than 14 times compared with raw CC.
In addition, the synthesized material had the potential to be reused for at least five cycles
with minimal loss of adsorption capacity and efficiency. Moreover, the results confirmed
that HCC-Mg can be used as an efficient, sustainable adsorbent of Pb from polluted water
Obtaining Zn2+ from sphalerite concentrate
No full textValorization of zinc from polymetallic ores and concentrates is a very important branch in the metallurgical industry. Zinc is mostly extracted by hydrometallurgical methods. Leaching is most often done with the help of strong oxidizing agents, which can have a harmful effect on the environment. Certain cyclic oxidation systems, such as the Fe3+/Fe2+ couple, often fail to achieve a high level of zinc leaching, especially when it is in the form of sulfide. In this work, a new oxidation system was applied, which consists of MnO2 as the primary oxidation agent and KI as a supporting oxidation agent that serves to form the I2/I- oxidation cycle in the medium of sulfuric acid. The leaching experiment was performed under atmospheric pressure conditions, in the temperature range from 40 to 80 °C. The influence of KI concentration on the degree of zinc leaching was also examined. For the mentioned system, the degree of zinc extraction is 89.78% after 3 hours of leaching at a temperature of 80 °C. These results show that the MnO2-KI oxidation system has the potential to improve zinc extraction from sphalerite concentrates
Improving agglomerates through coating
No full textCoating is a surface modification technique frequently applied to agglomerates to improve performance, handling, appearance, and integrity. The process involves applying a thin layer of material to pellets or granules, offering benefits such as reduced dust formation, improved flowability, moisture resistance, and controlled solubility. This paper discusses the key advantages of coating, the selection of appropriate coating materials, and equipment used for application, with reference to industry practices and relevant literature
From Fruit Waste to Water Purifier: Plum Stone-Derived Biochar for Malachite Green Removal
No full textAgriculture is a crucial sector of Serbia's economy, with approximately 5 million hectares of agricultural land, accounting for about 55% of the country's territory. The fruit production/processing industry plays a significant role in economy revenue. The annual fruit production accounts around 1.5 million tons, where the plum production is approximately 380,000 t/y, positioning Serbia as one of the world's leading producers of plums. Beside the pruning waste, the plum production and processing result in nearly 11,000 tons of plum stones (PLS). Currently, there is no structured system for the collection or repurposing of this byproduct, leading to its disposal in landfills or through incineration. In this paper, PLS, a renewable, low-cost, and sustainable byproduct of the fruit processing industry, was utilized to produce biochar (PLS-B) through thermochemical conversion (pyrolysis). The resulting biochar was characterized through Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), and zeta potential analysis. It was subsequently used as an adsorbent for the removal of the carcinogenic dye Malachite Green (MG) from water solution. Results demonstrated that PLS-B possesses a highly developed porous structure and a negatively charged surface, which facilitates the adsorption of cationic molecules such as MG. The adsorption isotherm of MG on PLS-B was determined by mixing 0.1 g of PLS-B with 50 mL of MG solution (10–350 mg/L) at room temperature for 24 h (batch system). The experimental data were fitted with Langmuir, Freundlich, and Sips isotherm models. The Sips isotherm model provided the best fit, with a maximum adsorption capacity of 99.89 mg/g. The utilization of fruit industry waste to produce an efficient adsorbent offers a potential solution to disposal challenges, reduces environmental pollution on local, regional, and global scales, and simultaneously purifies wastewater contaminated with toxic dyes
Dissolution Behavior of Sintered Phosphate Glasses with Strontium and Lanthanum Addition in Simulated Body Fluid
No full textThe dissolution behavior of sintered GSSr and GSLa phosphate
glass samples in simulated body fluid (SBF) was investigated to
evaluate their chemical stability and degradation mechanisms.
The study involved mass loss measurements, pH monitoring,
and elemental concentration analysis over a 21-day period. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to assess surface and structural modifications.
GSSr samples sintered at both maximum shrinkage temperature
(Tms) and maximum crystallization temperature (Tp) exhibited minimal mass loss (<0.2%) at all experimental time points. The
pH of the surrounding SBF solution remained stable, confirming
the low dissolution rate. SEM analysis showed no significant
surface changes. In contrast, GSLa samples displayed variable
dissolution behavior. The sample sintered at Tms (565°C) exhibited the highest mass loss (~18%) over the longest
experimental duration, while samples sintered at Tp showed a slight mass increase (~3%). The observed pH decrease for the
Tms sample suggests phosphate network breakdown due to
hydrolysis of P-O-P bonds, whereas Tp samples maintained a
more stable pH, indicating reduced solubility. Elemental analysis revealed that concentrations of P, Sr, and Na increased
with immersion time in GSSr samples, while Ca concentrations
remained below those in the initial SBF solution. GSLa samples
sintered at Tms showed increasing P concentrations up to 336
hours, followed by a decline, whereas Tp samples exhibited a
more stable elemental release profile. These findings highlight
the superior stability of GSSrglasses in SBF, making them
suitable for biomedical applications requiring long-term
durability, whereas GSLa glasses demonstrate tunable solubility
based on sintering conditions, offering potential for
bioresorbable materials
The global market of PET production: from origins to recycling
No full textPlastic handling and manufacturing have recently increased dramatically owing to
technological advancements and rising living standards. Consequently, the amount of plastic
waste has significantly escalated, seriously pressuring the whole ecosystem. The impacts of
waste accumulation in the environment frequently have detrimental effects on living organisms.
Sustainable development goals (SDGs) propose balanced and feasible development of entire
humanity, protecting natural resources and bringing a clean environment. Poly (ethylene
terephthalate) - PET is a common plastic that can seriously threaten the environment if it is
not handled appropriately. This review paper tends to show recent trends in the production
and recycling of PET polymer on a global scale. The basis of PET chemistry together with
possible applications was presented. A target period, from 2020-2024, was used to examine
the quantity and main industrial suppliers around the world. Therefore, some sources state
that in 2024, nearly 28 Mt of PET was produced and China was the main producer with a
global share of 31%. Adequate management of the mentioned polymer is necessary for
building an eco-friendly climate for future generations