Hydrochloric Research Articles

Study on adsorption of scandium by iminodiacetic acid resin TP207

Abstract Scandium (Sc) is a rare transition metal applied in unique electronic/alloy materials such as magnesium scandium alloy, aluminum scandium alloy, laser glass, superconductors, and electronic components. However, scandium is extremely hard to obtain. In this paper, the iminodiacetic acid resin TP207 was first applied for the recovery of scandium from a hydrochloric acid solution. The adsorption of Sc3+ by TP207 resin was analyzed by SEM-EDS, FT-IR, and XPS. It was found that the best adsorption time was 2 hours with the equilibrium adsorption rate reaching 99%. The saturated adsorption amount of resin was 0.05g/ml. This process involves the ion exchange of scandium ions with sodium ions on the resin and the chemisorption of scandium with the -COO- group. Furthermore, the TP207 resin exhibited a quasi-second-order kinetic mechanism towards Sc3+, which was the rate of adsorption is proportional to the concentration of the reactants. In addition, the adsorption of resin for Sc3+ is an endothermic reaction by calculating the thermodynamic parameters, and there is a 3.6% difference in adsorption efficiency between the two cycle experiments. In a word, the TP207 resin is a very promising adsorbent for Sc beneficiation from the HCl system.

Leaching Efficiency of 238U and 232Th series from Granitic Soils

Granitic soil, a uranium (U) and thorium (Th)-bearing soil body, can be sourced to extract fissionable nuclides through leaching using acidic solutions. Limited research indicates the feasibility of extracting U and Th from granitic sources, necessitating further studies to optimize leaching efficiency and its potential as a fissionable fuel. This study investigates the leaching efficiency of the uranium 238U and thorium 232Th series, as well as 40K, in granitic soil samples. The study utilized a high-purity germanium detector (HPGe) to quantify the activity levels of the 238U and 232Th series and 40K in the studied samples. The black sand deposit and tin-tailing samples were also utilized to benchmark the finding of the leaching efficiency of the uranium 238U and thorium 232Th in granitic samples. The study found that the leaching samples contained low radioactivity levels that were a few to tenth times lower compared to the original samples, with tin-tailing samples exhibiting the highest leaching activity for 238U (630.05 Bq l-1) and 232Th (512.17 Bq l-1) and comparable to granitic soil samples 238U (437.7 Bq l-1) and 232Th (23.9 Bq l-1). Sulfuric acid showed the most efficient leaching reagent ~ up to 23% and 32% for 232Th and 238U, respectively. In comparison, nitric and hydrochloric acids exhibited low leaching efficiencies, ~ 1 – 13%. Overall, granitic soil shows comparable leaching rates to conventional sources of natural uranium nuclear fuel, making it a potential secondary and alternative nuclear fuel source.

Facile synthesis, corrosion inhibition, adsorption and DFT studies of 2-(4-(methylsulfanyl) phenyl) −4, 5-diphenyl-1H-imidazole for mild steel in acidic environment

A green, solvent-free, cost effective one-pot synthesis method is employed to produce the innovative corrosion-inhibiting compound 2-(4-(methylsulfanyl)phenyl)-4,5-diphenyl-1H-imidazole (MDPI). The molecular structure of MDPI can be identified using CHN analyses, FT-IR, 1H and 13C NMR spectra. Various electrochemical and gravimetric techniques are utilized to evaluate the anti-corrosion properties of MDPI. The results indicate that MDPI effectively inhibits the corrosion of mild steel under all tested conditions. At 306 K, MDPI achieved a maximum corrosion inhibition efficiency of 98.01 % at a concentration of 10 mM. MDPI exhibited strong adsorption and excellent anti-corrosion properties, forming a protective layer on the mild steel surface. The Langmuir adsorption isotherm, with a ΔGoads value of −39.55 kJ/M was found to be more suitable for this study, indicating that the process occurred by physisorption. Tafel curves indicated that MDPI functions as a mixed-type corrosion inhibitor. Surface characteristics were analyzed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM). Quantum chemistry studies revealed a HOMO-LUMO energy gap of 3.926 eV, corroborating the anti-corrosion effectiveness of MDPI in hydrochloric acid solution. MDPI exhibited promising anti-corrosion activity due to its heterocyclic ring containing nitrogen heteroatoms as well as a methylsulfanyl functional group.

Performance and mechanism of phytic acid-modified mesoporous tobermorite for U(VI) adsorption in water

Tobermorite (TOB) was first prepared with waste fly ash and calcium carbide slag by the hydrothermal method, and then TOB was subjected to thermal activation, hydrochloric acid acidification, and phytic acid modification to synthesize phytic acid-modified mesoporous tobermorite (P-STOB). The adsorption results showed that the maximum adsorption ratio of U(VI) by P-STOB could achieve 99.17 %, significantly higher than that of TOB (79.20 %). Moreover, under conditions of pH=5, T=303 K, and an initial U(VI) concentration of 10 mg/L, the theoretical uptake capacity for U(VI) by P-STOB was 176.66 mg/g. Pseudo-second-order and Langmuir isotherm adsorption models fit the adsorption process well, which indicated that the adsorption process was mainly chemical adsorption and primarily monolayer adsorption. Thermodynamic parameters revealed that the U(VI) adsorption was an endothermic and spontaneous process. The Dubinin-Radushkevich model suggests that the adsorption mechanism is surface chemical complexation. Even after five cycles, the U(VI) removal ratio remained above 74.63 %. Characterizations using SEM, EDS, XRD, BET, XPS and FT-IR confirmed the successful introduction of phytic acid onto the surface of P-STOB. The main mechanism of the adsorbent's interaction with U(VI) is the coordination between P-O and U(VI), the surface complexation between -OH and U(VI), and the electrostatic gravitational force between ions.

Efficient removal of cadmium and lead in water by using nano-manganese oxide-loaded hydrochloric acid pretreated biochar

Cadmium (Cd) and lead (Pb) contaminated water pose a serious threat to the safety of aquatic organisms and human food, which is a hot topic in the world. To improve the removal efficiency of straw biochar (BC) on Cd and Pb pollution water, the modified biochar (BCHMn) was manufactured by loading nano-manganese oxide (nano-MnOx) on hydrochloric acid pretreated BC. The adsorptive properties of Cd2+ and Pb2+ for BCHMn were examined by isothermal, kinetic adsorption models, and cycle tests. The results indicated that the adsorption of Cd2+ and Pb2+ by BCHMn is suitable for Langmuir, Sips, Avrami, and pseudo-second-order kinetic model, suggesting monolayer and heterogeneous chemical adsorption. The maximum theoretical adsorptive amount of Cd2+ and Pb2+ on BCHMn are 108.21 mg/g and 312.16 mg/g, respectively. The adsorption mechanism of BCHMn is primarily mineral precipitation, π electron interaction, and ion exchange. Moreover, BCHMn contained the special birnessite (δ-MnO2) structures and MnOx, which can form stable complexes with Cd/Pb (such as Mn-O-Cd/Pb and Mn-R-O-Cd/Pb). These results indicate that BCHMn can efficiently remove Cd2+ and Pb2+ from water, and provide a reference for the comprehensive utilization of straw waste and water pollution control.

Pseudogenization of NK3 homeobox 2 (Nkx3.2) in monotremes provides insight into unique gastric anatomy and physiology.

The enzymatic breakdown and regulation of food passage through the vertebrate antral stomach and pyloric sphincter (antropyloric region) is a trait conserved over 450 million years. Development of the structures involved is underpinned by a highly conserved signalling pathway involving the hedgehog, bone morphogenetic protein and Wingless/Int-1 (Wnt) protein families. Monotremes are one of the few vertebrate lineages where acid-based digestion has been lost, and this is consistent with the lack of genes for hydrochloric acid secretion and gastric enzymes in the genomes of the platypus (Ornithorhynchus anatinus) and short-beaked echidna (Tachyglossus aculeatus) . Furthermore, these species feature unique gastric phenotypes, both with truncated and aglandular antral stomachs and the platypus with no pylorus. Here, we explore the genetic underpinning of monotreme gastric phenotypes, investigating genes important in antropyloric development using the newest monotreme genomes (mOrnAna1.pri.v4 and mTacAcu1) together with RNA-seq data. We found that the pathway constituents are generally conserved, but surprisingly, NK3 homeobox 2 (Nkx3.2) was pseudogenized in both platypus and echidna. We speculate that the unique sequence evolution of Grem1 and Bmp4 sequences in the echidna lineage may correlate with their pyloric-like restriction and that the convergent loss of gastric acid and stomach size genotypes and phenotypes in teleost and monotreme lineages may be a result of eco-evolutionary dynamics. These findings reflect the effects of gene loss on phenotypic evolution and further elucidate the genetic control of monotreme stomach anatomy and physiology.

Enhanced antimicrobial activity of photocatalytic titanium oxide upon formation of composites with polyaniline via an eco-friendly and facile microwave synthesis approach

This study proposes inexpensive antimicrobial polyaniline-titanium oxide (PANI-TiO2) samples prepared through eco-friendly enhanced microwave (MW) synthesis with 93 W applied over 10 min in aqueous 1.25 M hydrochloric acid media (HCl) using potassium iodate (KIO3) as oxidising agent, an approach suitable for industrial scale up production of PANI polymers at room temperature. The PANI-TiO2 samples are produced in the presence of 5–20 wt% of TiO2 in the initial reaction mixture along with aniline monomer by both the enhanced MW method and a classical chemical synthesis (CS) method at room temperature. The nanocomposites showed lower conductivity than pure PANI, slightly higher conductivity was observed in the MW prepared PANI-TiO2 in comparison to CS prepared PANI-TiO2. This result can be correlated with the observation that the optical absorbance of MW PANI-TiO2 samples were notable higher than for CS PANI-TiO2, which may be due to the presence of a greater amount of polarons present in the samples prepared by the enhanced MW method. MW PANI-TiO2 samples were equally active against both Gram-negative E. coli and Gram-positive S. aureus bacteria, in contrast to the CS PANI-TiO2 samples, which could be due to presence of short-chain fragments in the CS samples as confirmed by Fourier-transform infrared (FTIR) spectroscopy. The incorporation of PANI particles in TiO2 showed enhanced antimicrobial activity compared to pure TiO2, with greater antifungal activity. Our study indicates that a facile, low-cost, and green enhanced MW method can be used for preparation of the advanced antimicrobial PANI-TiO2 nanocomposites for biomedical applications.

Synthesis and Characterization of New Azo Dye Derived from Sulfamethaxolevia Diazonium Reaction and Study its Abilityas an Acid-base Indicator

Background: Most azo dyes are synthesized by diazotization of a primary amine, followed by conjugation with one or more electron-rich nucleophiles. Objective: This study presents the synthesis of a new azocompound by converting sulfamethoxazole to a diazonium salt. Methods: via reaction with hydrochloric acid and sodium nitrite at temperatures between 0 and 5 °C, the resulting salt is then coupled with a 4-methoxyphenol reagent in alkaline medium at the above temperatures to produce an azodye given the IUPAC name of (4-((2-hydroxy-5-methoxyphenyl)diazenyl)-N-(5-methylisoxazol-3yl)benzenesulfonamide). The azo dye precipitate was purified by crystallization methods using a solvent mixture of ethanol water. Characterization was done using different analytical methods such as IR, UV-Vis and H1-NMR in addition to measurements of physical properties. Results: The reddish-pink azo compound gave a maximum absorbance of 495 nm. Acid-base titrimetric analysis was conducted to examine the chemical indicator properties of the azo dye. Clear color differences were obtained between two spaces in the pH range 2-12, where a reddishpink color was obtained in the basic medium and a yellow color in the acidic medium. Conclusions: A new azo dye successfully presented its properties as an indicator.

The Demineralization Optimization for Chitosan Synthesis from Crab Shell Waste (Portunus pelagicus)

Chitosan, gelatin, albumin, and sodium alginate are examples of natural polymers that are often utilized as a basis material for polymeric nanoparticles. The deacetylation of chitin molecules produces the formation of chitosan. Chitin, protein, CaCO3, MgCO3, and astaxanthin pigment are all found in crab shells. Crab shell is an undervalued potential waste. Despite the fact that copious crab shell waste can be used to produce raw materials and industrial products. According to the findings of Mohadi et al (2014), chitosan was extracted with a yield of 70.71% and a deacetylation degree of 76.6%. Previous research on optimizing chitosan synthesis has involved changing the base reagent at the deacetylation stage. The results showed that a 50% concentration of KOH reagent produced the best chitosan properties. Another study on the synthesis of chitosan from crab shells got a yield of 70.4%, and the following analysis showed that this high yield is due to the amount of calcium. Therefore, demineralization in the synthesis of chitosan from crab shells must be optimized. The calcium content was measured after optimization with various solvent concentration variations. The best demineralization optimization results use 3 M hydrochloric acid with a decrease in calcium content of 97.75%.

Impact of weak organic acids as coagulants on tailoring the properties of cellulose aerogel beads

Tailoring the properties of cellulose aerogel beads was investigated in the present study by using weak organic acids as coagulants. Three different weak acids were specifically chosen, acetic acid, lactic acid and citric acid. For comparative studies, a strong acid, hydrochloric acid was examined. The production of aerogel beads by conventional dropping technique was controlled and optimized for weak acids. Aerogels were characterized by density analyses, scanning electron microscopy, nitrogen adsorption–desorption analysis, X‐ray powder diffractometry and IR spectroscopy. In common, all the aerogel beads showed interconnected nanofibrillar network, high specific surface area, high pore volume, high porosity and meso‐ and macroporous structure. In particular, when the weakest acid (acetic acid) was used as coagulant in the regeneration bath, the lowest shrinkage was observed. As a result, the cellulose aerogel beads produced from acetic acid showed the highest values of specific surface area (423 m2·g‐1) and pore volume (3.6 cm3·g‐1). The porous structure can be tuned by the choice of regeneration bath having either strong acid or high concentration of weak acid. The aerogel beads were pure and showed cellulose II crystallinity. Hence this study paves an alternative path way to tailor the properties of cellulose aerogel beads.

Chemical Modifications of Recycled Concrete Aggregate

The necessity for environmental sustainability has prompted the utilization of recycled concrete aggregates (RCA) sourced from structural demolition sites for the production of recycled aggregate concrete (RAC). The primary element impacting the quality of recycled concrete aggregate (RCA) is the mortar paste that adheres to the natural aggregate (NA). The cement mortar adhered to recycled concrete aggregate exhibits higher porosity and water absorption levels, along with reduced strength compared to natural aggregate. These characteristics negatively impact both the mechanical properties and durability of fresh and hardened concrete incorporating recycled concrete aggregate. As a result, it is crucial to enhance the interface by improving the surface of the aggregate or by removing the mortar adhered to the NA. Methods for achieving this include surface modification of the aggregate or removing adhered paste from the natural aggregate (NA). This research includes treatment involving acidic solutions particularly hydrochloric acid (HCl), and sulphuric acid (H2SO4), for mortar layer removal from RCA, analyzing their impact on the mechanical properties of aggregates and durability of concrete incorporating RCA.

Chemical Transformations of Benzyl Alcohol Caused by Atomic Chlorine.

Atomic chlorine present in the polluted troposphere can form potentially carcinogenic compounds as a result of a reaction with a natural product. This paper examines the stability of benzyl alcohol-a natural product commonly found in cosmetics-in interaction with atomic chlorine, which is becoming ever more present in the Earth's atmosphere as a result of its pollution. Research shows that atomic chlorine generated in the gas phase easily penetrates the liquid phase of benzyl alcohol, resulting in the formation of hydrochloric acid. The resulting HCl initiates further transformations of benzyl alcohol. Our study presents the amounts of the reaction products. The quantitative analysis was made using the GC method, and all the products were identified using the GC-MS method. The products include dichloromethyl benzene, 2-chlorobenzyl alcohol, and 3-chlorobenzyl alcohol, which are harmful, but are formed in very small amounts. The harmful substance occurring in a much higher amount is benzyl chloride-that is a product of acidification of benzyl alcohol by HCl.

Removal of Heavy Metal Ions from Water Using Chelating Copolymer Resin-IV Derived from 2-Hydroxy, 4-Methoxybenzophenone, 1, 5-Diaminonaphthalene and Formaldehyde

The resin 2-H, 4-MBP-1,5-DANF-IV was synthesized by the condensation of 2-hydroxy, 4-methoxybenzophenone and1, 5-diaminonaphthalene with formaldehyde in the presence of hydrochloric acid as a catalyst. The resin was characterized by elemental analysis, infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and UV-Visible spectral studies. The chelation ion-exchange properties was studied for Ni2+, Cu2+, Co2+, Zn2+ and Pb2+ ions employing a batch equilibrium method. It was used to study of the selectivity of metal-ion uptake involving the measurements of the distribution of a given metal ion between the copolymer sample and a solution containing the metal ion. The study was carried out over a wide pH range and in media of various ionic strength.The resin depicted a higher selectivity for Cu2+ and Ni2+ ion than for Co2+, Zn2+ and Pb2+ ions.

Study of the Resistance of Staphylococcus aureus Biofilm, Biofilm-Detached Cells, and Planktonic Cells to Microencapsulated Carvacrol Used Alone or Combined with Low-pH Treatment.

Microbial biofilms pose severe problems in the medical field and food industry, as they are the cause of many serious infections and food-borne diseases. The extreme biofilms' resistance to conventional anti-microbial treatments presents a major challenge to their elimination. In this study, the difference in resistance between Staphylococcus aureus DSMZ 12463 biofilms, biofilm-detached cells, and planktonic cells against microcapsules containing carvacrol was assessed. The antimicrobial/antibiofilm activity of low pH disinfection medium containing the microencapsulated carvacrol was also studied. In addition, the effect of low pH on the in vitro carvacrol release from microcapsules was investigated. The minimum inhibitory concentration of microencapsulated carvacrol was 0.625 mg mL-1. The results showed that biofilms exhibited greater resistance to microencapsulated carvacrol than the biofilm-detached cells and planktonic cells. Low pH treatment alone, by hydrochloric acid addition, showed no bactericidal effect on any of the three states of S. aureus strain. However, microencapsulated carvacrol was able to significantly reduce the planktonic cells and biofilm-detached cells below the detection limit (no bacterial counts), and the biofilm by approximatively 3 log CFU mL-1. In addition, results showed that microencapsulated carvacrol combined with low pH treatment reduced biofilm by more than 5 log CFU mL-1. Thus, the use of microencapsulated carvacrol in acidic environment could be a promising approach to combat biofilms from abiotic surfaces.

Molecular recognition on the surface of concentrated hydrochloric acid: Hydration configuration-driven preferential recognition of Rh (III) anions with inner-coordinated water molecules

Comprehension of selective recognition of anions is confined to a phenomenological list of solvents, hardly surpassing Pedersen’s empirical observations of cationic-crown ether binding. In this work, a novel strategy employing thin-layer oil membrane extraction (TOMX) on the surface of concentrated hydrochloric acid is proposed for controllable recognition and separation of anions with different hydration configurations. Four typical chloric-complexing anions, RhCl63−, PdCl42−, PtCl62− and FeCl4−, usually coexisting in the concentrated hydrochloric acid leaching solutions of precious metal concentrates were focused. A surprising phenomenon was noticed that the octahedral RhCl5(H2O)2− anions with inner-coordinated water molecules were preferentially recognized by 18C6 macrocyclic molecule. However, the planar quadrilateral Pd (II) chloric-complexing anions with a hydration configuration via water molecules attacking the central Pd (II) atoms along the Z-axis direction can be separated subsequently. The Pt (IV) and Fe (III) chloric-complexing anions respectively with an octahedral and tetrahedral outer-coordinated hydration shell configuration were the last to be recognized. Such an order in extracting Rh (III) > Pd (II) > Pt (IV) > Fe (III) anions depends on their hydration capacity and the preferential affinity towards the interface, which is almost impossible during the conventional stirring and oil droplet dispersed extraction. Because of a lower concentration of dissociated hydrogen ions on the surface of concentrated hydrochloric acid compared to its bulk concentrations, the hydration of those chloric-complexing anions was enhanced. The Rh (III) anions with inner-coordinated water molecules exhibit a higher interfacial affinity than other anions. The water molecules entering the inner coordination layer of Rh (III) chloric-complexing anions, cooperating with its outer-coordinated hydration shell, act as a hydrogen bond “water bridge” to interact with 18C6 molecules, which makes it easier to feel the influence from the aqueous laminar shear flow under the thin-layer oil membrane, thereby driving the preferential recognition of easily hydrated Rh (III) anions at the interface. The controllable “water bridge” interactions driven by shear flow can be activated or deactivated on the surface of concentrated hydrochloric acid by adjusting the shear flow rate. This work lays a foundation for the future development of a controllable flexible molecular recognition technology at liquid–liquid interfaces.

Effect of Hydrochloric Acid Hydrolysis under Sonication and Hydrothermal Process to Produce Cellulose Nanocrystals from Oil Palm Empty Fruit Bunch (OPEFB).

This paper presents an approach for hydrolyzing cellulose nanocrystals from oil palm empty fruit bunch (OPEFB) presented through hydrochloric acid hydrolysis under sonication-hydrothermal conditions. Differences in concentration, reaction time, and acid-to-cellulose ratio affect toward the yield, crystallinity, microstructure, and thermal stability were obtained. The highest yield of cellulose nanocrystals up to 74.82%, crystallinity up to 78.59%, and a maximum degradation temperature (Tmax) of 339.82 °C were achieved through hydrolysis using 3 M HCl at 110 °C during 1 h. X-ray diffraction analysis indicated a higher diffraction peak pattern at 2θ = 22.6° and a low diffraction peak pattern at 2θ = 18°. All cellulose nanocrystals showed a crystalline size of under 1 nm, and it was indicated that the sonication-hydrothermal process could reduce the crystalline size of cellulose. Infrared spectroscopy analysis showed that a deletion of lignin and hemicellulose was demonstrated in the spectrum. Cellulose nanocrystal morphology showed a more compact structure and well-ordered surface arrangement than cellulose. Cellulose nanocrystals also had good thermal stability, as a high maximum degradation temperature was indicated, where CNC-D1 began degrading at temperatures (T0) of 307.09 °C and decomposed (Tmax) at 340.56 °C.

Indirect Spectrophotometric Determination of Antidepressant Drugs by Oxidation Using Ponceau 4R Dye

A simple and sensitive indirect spectrophotometric method is developed for the assay of Adrenaline, Dopamine hydrochloride, and Methyldopa in their pure and pharmaceutical preparations. The method is based on the principle of oxidation of the above drugs with a known amount of the oxidizing agent, N-bromosuccinimide (NBS), in hydrochloric acid. The unreacted oxidant bleaches Ponceau 4R dye, then the absorbance of the remaining dye (ΔA) is measured at 507 nm. The method obeyed Beer’s law within the concentration range of 3.5-10, 4-15, and 5-20 μg/mL, with molar absorptivity values of 8.01×104, 5.32×104, and 4.93×104 L. mol-1cm-1 for Adrenaline, Dopamine hydrochloride and Methyldopa, respectively. The recovery ranged between 99.15 to 100.61%, and the relative standard deviation (RSD) was less than 1.42 % for all drug compounds. The method was applied successfully to pharmaceutical preparations for the studied medicinal compounds from different origins, as its results were in good agreement with the original content of the drugs in their pharmaceutical formulations and with the standard addition procedure, which proved that there was no interference by the excipients.

Developing a novel imine derivative as a corrosion inhibitor for Q235 carbon steel in 1 M HCl solution: Experiments and theoretical calculations

During oil and gas extraction, metals are inevitably exposed to acidic environments on a regular basis. Acid solutions, particularly hydrochloric acid, are employed in a multitude of industrial processes, including oil well acidising, steel pickling, ferroalloy pickling and acid cleaning. These applications frequently result in severe metal corrosion. To cope with corrosion, the superlative simple and effective method is to prevent corrosion inhibitors. Naphthyridinimides are not as effective as rust inhibitors, but their corrosion inhibition is significantly improved by the addition of Br ions. This thesis focuses on the synthesis of naphthylimine-type novel organic corrosion inhibitors and the corrosion inhibition mechanism, with the main content of 3,3′-(1,3,6,8-tetraoxo-1,3 6,8-tetrahydrobenzo[lmn] [3,8] phenanthroline-2,7-diyl) bis (N-ethyl -N, N-Dimethyl-1-propylamine) bromide (NDI-N-Br) on Q235 carbon steel in an acidic environment (1 M hydrochloric acid solution). The corrosion inhibition efficiencies of NDI-N-Br reached 93.53 % at 300 ppm at an ambient temperature of 298 K. The corrosion inhibitor NDI-N-Br forms a protective film on the metal surface and organizes the interaction between the metal matrix and the corrosive medium, providing a rust inhibiting effect. This thesis shows that this class of compounds can be well applied to acidic environments and provide ideas for the subsequent development of naphthylimide-based organic corrosion inhibitors.

Determinants of hemoglobin level and time to default from Highly Active Antiretroviral Therapy (HAART) for adult clients living with HIV under treatment; a retrospective cohort study design

HIV/AIDS is one of the most devastating infectious diseases affecting humankind all over the world and its impact goes beyond public health problems. This study was conducted to investigate the joint predictors of hemoglobin level and time to default from treatment for adult clients living with HIV/AIDS under HAART at the University of Gondar Comprehensive and Specialized Hospital, North-west Ethiopia. The study was conducted using a retrospective cohort design from the medical records of 403 randomly selected adult clients living with HIV whose follow-ups were from September 2015 to March 2022. Hemoglobin level was projected using Sahli’s acid-hematin method. Hence, the hemoglobin tube was filled with N/10 hydrochloric acid up to 2 g % marking and the graduated tube was placed in Sahli’s hemoglobin meter. The blood samples were collected using the finger-pick method, considering 22 G disposable needles. The health staff did this. From a total of 403 adult patients living with HIV/AIDS included in the current study, about 44.2% defaulted from therapy. The overall mean and median estimated survival time of adult clients under study were 44.3 and 42 months respectively. The patient’s lymphocyte count (AHR = 0.7498, 95% CI: (0.7411: 0.7587), p-value < 0.01), The weight of adult patients living with HIV/AIDS (AHR = 0.9741, 95% CI: (0.9736: 0.9747), p-value = 0.012), sex of adult clients (AHR = 0.6019, 95% CI: (0.5979, 0.6059), p-value < 0.01), WHO stages III compared to Stage I (AHR = 1.4073, 95% CI: (1.3262, 1.5078), p-value < 0.01), poor adherence level (AHR = 0.2796, 95% CI: (0.2082, 0.3705) and p-value < 0.01), bedridden patients (AHR = 1.5346, 95% CI: (1.4199, 1.6495), p-value = 0.008), and opportunistic infections (AHR = 0.2237, 95% CI: (0.0248, 0.4740), p-value = 0.004) had significant effect on both hemoglobin level and time to default from treatment. Similarly, other co-morbidity conditions, disclosure status of the HIV disease, and tobacco and alcohol addiction had a significant effect on the variables of interest. The estimate of the association parameter in the slope value of Hgb level and time default was negative, indicating that the Hgb level increased as the hazard of defaulting from treatment decreased. A patient with abnormal BMI like underweight, overweight, or obese was negatively associated with the risk of anemia (lower hemoglobin level). As a recommendation, more attention should be given to those patients with abnormal BMI, patients with other co-morbidity conditions, patients with opportunistic infections, and low lymphocytes, and bedridden and ambulatory patients. Health-related education should be given to adult clients living with HIV/AIDS to be good adherents for medical treatment.

Chitin Nanocomposites for Fused Filament Fabrication: Flexible Materials with Enhanced Interlayer Adhesion.

In this work, we present a series of nanocomposites for Fused filament fabrication (FFF) based on polycaprolactone (PCL) and chitin nanocrystals (ChNCs). The ChNCs were synthesized by acid hydrolysis using HCl or lactic acid (LA). The approach using LA, an organic acid, makes the ChNCs synthesis more sustainable and modifies their surface with lactate groups, increasing their compatibility with the PCL matrix. The ChNCs characterization by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy revealed that both ChNCs presented similar morphologies and crystallinity, while differential scanning calorimetry and thermogravimetric analysis proved that they can bear temperatures up to 210 °C without degrading, which allows their processing in the manufacturing of PCL composites by twin-screw extrusion. Therefore, PCL composites in the form of filaments containing 0.5-1.0 wt % ChNCs were produced and used as feedstock in FFF, and standard tensile and flexural specimens were printed at different temperatures, up to 170 °C, to assess the influence of the ChNCs in the mechanical properties of the material. The tensile testing results showed that the presence of ChNCs enhances the strength and ductility of the PCL matrix, increasing the elongation at break around 20-50%. Moreover, the vertically printed flexural specimens showed a very different bending behavior, such that the pure PCL specimens presented a brittle fracture at 7% strain, while the ChNCs composites were able to bend over themselves. Hence, this work proves that the presence of ChNCs aims to improve the interlayer adhesion of the objects manufactured by FFF due to their good adhesive properties, which is currently a concern for the scientific community and the industrial sector.