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Hydrodynamic Study of a Hybrid Electro-Flotation Column

Bubble columns are used in the mining industry for mineral recovery but are also widely utilized in the chemical and petrochemical industry. The hydrodynamic characteristics of their performance is a field of interest with a number of points, which are nonetheless poorly understood, and a considerable amount of methods have aimed to shed light on the flow regimes that prevail in the columns. The study of the hydrodynamic part of a flotation process should consider characteristics such as air flow, volumetric gas fraction, flow field, and bubble size, along with the mechanical and design factors and pulp properties. The present work aims to elucidate the characteristics of the gas phase of a hybrid flotation system. For this purpose, a hybrid flotation column was designed and constructed and the bubbles size distributions at different radial positions in the flotation column were computed by analyzing high resolution digital images. A patented electrical impedance technique was employed to instantaneously measure the local volumetric gas fraction. Flow dispersion in the column was studied by residence time distributions using conductivity tracers. The experimental results are discussed to comprehend the variation in the gas fraction in the column. In particular, the study showed that the size of the bubbles changed from the center to the walls of the column, and this was observed both radically and vertically. Moreover, the size of the bubbles affected the volume fractions, and no coalescence of the bubbles was observed. Finally, the dispersion of the tracer in the working solution was distributed uniformly in the volume of the column, with a time difference for the four positions of the column.

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Life cycle carbon analysis of packaging products containing purposely grown nonwood fibers: A case study on the use of switchgrass pulp for linerboard and corrugating medium

Sustainability is driving innovation in the pulp and paper industry to produce goods with lower carbon footprints. Although most of the efforts are currently focused on increasing energy efficiency or switching to renewable fuels, the attention toward alternative feedstocks has increased in recent years. Claims of nonwood fibers requiring lower use of chemicals and energy than wood fibers, along with negative consumer perceptions of tree felling, are helping purposely grown nonwoods to gain market share. The potential nonwood fiber environmental superiority over virgin or recycled wood fibers remains controversial and is often driven more by emotion and public perception rather than facts. This paper estimates the carbon footprint of corrugating medium and linerboard containing switchgrass pulp compared to analogous wood-based materials. The study includes a life cycle carbon analysis spanning from cradle to gate, which comprises stages for fiber production, pulping, papermaking, and corresponding transportation. Carbon footprints for virgin linerboard, recycled linerboard, virgin medium, and recycled medium were estimated at around 510, 620, 460, and 670 kg carbon dioxide equivalent per metric ton (kg CO2eq/t), respectively. Replacing 30% of the virgin or recycled material with switchgrass pulp translated into carbon footprint increases of around 60%, 45%, 62%, and 38%, respectively. Thus, for the proposed case study, the results suggest that switchgrass-based medium and linerboard can present a higher carbon footprint than products made from virgin and recycled wood fibers. The main driver is the production of nonwood mechanical pulp. This study was designed to mitigate part of the uncertainty around the environmental sustainability of medium and linerboard made from the selected purposely grown nonwood fibers.

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Investigation into the characteristics of bagasse processed with 3C-DES and the production of chemimechanical pulp for pulp molded

Pulp molded generated from renewable bagasse as biodegradable packaging materials has been widely viewed as an eco-friendly and cheap way to substitute the current huge consumption of nondegradable plastics, and deep eutectic solvents (DES) pretreatment are a promising approach to obtain high-yield pulp efficiently and sustainably. However, mainstream binary-component DES still suffers issues of high viscosity and corrosiveness. This study put forward a ternary-component DES (3C-DES) with the addition of ethylene glycol (EG) into choline chloride (ChCl) and P-toluenesulfonic acid (PTSA) and examined pretreatment performance and optimal DES ratio for thread rolling bagasse via compositional analysis and physicochemical characterization. Moreover, density functional theory calculations were used to reveal structures and weak interactions of different ratios of 3C-DES, and a novel 3C-DES pretreatment chemical-mechanical pulp and pulp molded were finally prepared. The results indicate that the 3C-DES with ChCl:PTSA:EG molar ratio of 1:1:3 is most effective, evidenced by more than 97.94% lignin removals. The 3C-DES pretreated mechanical pulp exhibits superior fiber properties, whereas the hot-pressed pulp molded shows excellent physical properties and thermal stability. Thus, the proposed 3C-DES has great potential to obtain high-yield high-performance pulp molded with low cost and environmental sustainability.

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Evaluation of Recycled Paperboard Properties and Characteristics

Paperboard boxes represent a sought-after class of packaging products, where the use of recycled fibers offers a cost-effective and environmentally friendly alternative to virgin fibers. The presence of a significant proportion of recycled fibers in the paperboard leads to a number of limitations associated with the deterioration of its characteristics. In this study, the properties of coated and uncoated paperboards containing recycled fibers, wood pulp, and virgin cellulose fibers were investigated using a laboratory sample of paperboard produced from 100% recycled fibers without any chemical additives for comparison. Properties such as smoothness, bulk density, absorbency, and tensile strength, as well as colorimetric characteristics, were determined for the recycled paperboards; for the latter test, charts were printed using inkjet printing and UV-curable inks. Whiteness was calculated by three formulae (CIE, Berger, and Stensby), and all the paperboards had a relatively low whiteness (not exceeding 90 CIE), with a yellowish tint due to recycled fibers and mechanical pulp in the composition. The absence of optical brightening agents in the paperboards was experimentally confirmed. The color gamuts of the paperboards were in direct ratio to their whiteness, with the highest ones demonstrated by the coated paperboards. Color reproduction, according to the tone value increase curves, also depended on the whiteness. Uncoated paperboards demonstrated smaller color shifts than the coated ones, with the greatest increase in tone for yellow color. Coated recycled paperboards are suitable for packaging printing under the same conditions as virgin fiber boards, while uncoated boards are the recommended choice for digital printing with UV inks.

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Morphometric parameters of dental pulp in immature teeth in a sheep model after mechanical pulp exposure and restoration with reinforced zinc oxide-eugenol

Background: The aim of the study was to investigate the morphometric parameters of dental pulp in open apices immature teeth in a sheep model after mechanical pulp exposure and restoration with reinforced zinc oxide-eugenol. Materials and Methods: In this experimental study, a total of 12 immature mandibular central incisors from six adult male sheep, weighing 30–40 kg and with the age of 1 year old with Merino race were examined. After anesthesia, the pulps of the teeth in the case group were mechanically exposed and then were restored with reinforced zinc oxide-eugenol and amalgam. In the control group, the teeth remained intact. The animals were sacrificed at intervals of 2, 4, 6, and 8 weeks (E2, E4, E6, and E8) in the case and 2 and 8 weeks (C2 and C8) in the control groups. Then, their teeth were removed with the surrounding supporting tissues and alveolar bones. Tissue processing and staining were done, and the sections were examined under a light microscope. The Kruskal–Wallis and Mann–Whitney U tests were used to analyze the data and compare the changes between the two groups. P < 0.05 was considered statistically significant. Results: In response to mechanical exposure, reparative or tertiary dentin was formed, and its thickness increased during the time of the study. The thickness of the odontoblastic layer in the E4 group was the highest amount. The pulp chamber diameter in the C2 group was significantly larger than the other groups, and the diameter of the apical foramen in the E8 was decreased significantly compared to the controls (P < 0.05). Conclusion: In response to mechanical exposure and restoration with reinforced zinc oxide-eugenol, some morphometric parameters of the dental pulp changed significantly in the sheep model compared to the controls.

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Evaluation for the efficacy of haemocoagulase agent (botroclot) as a pulpotomy material as compared to ferric sulfate- an animal study.

Deciduous teeth are thought to be best space maintainers; thus efforts are made to preserve these teeth for as long as possible. Grossly carious primary teeth should be restored and maintained which is the primary objective of “Pediatric dentistry”. Pulpotomy is done in the primary teeth where mechanical pulp exposure occurs during caries removal. All the functions of the radicular pulp are expected to be maintained by pulpotomy procedure. The main objectives are 1) managing reversible pulpal inflammation and keeping pulp in a vital condition. 2) maintain the function of the radicular pulp in deciduous teeth. Success of Pulpotomy procedure is dependent on many factors, and the ability of the pulpotomy medicament being hemostatic is one of the most vital factors to maintain the vitality of the radicular pulp. Considering the limitations of commonly used pulpotomy medicaments for primary teeth i.e. Formocresol and also the disadvantages associated with the hemostatic Ferric sulfate, the present study will be carried out using hemocoagulase (“botroclot”) which has shown improved hemocoagulant properties in the medical field and for healing the extraction socket wounds. The available solution of hemocoagulase agent converted in suitable Gel form will be tested for its tissue compatibility and hemocoagulant efficacy when used as pulpotomy material . The study will be conducted in two phases, I) Formulation of the gel and in vitro tests; II) Animal study to check histopathological effect on the pulp tissue as a pulpotomy agent.

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