Kraft Pulp Research Articles

Online monitoring of the size distribution of lime nodules in a full-scale operated lime kiln using an in-situ laser triangulation camera

To maximize efficiency of the recausticizing process in a pulp mill, producing a reburned lime with high and consistent reactivity is process critical. Prior investigations have demonstrated a correlation between the reactivity of lime and its nodule size, as well as the dusting behavior of the kiln. Therefore, monitoring the nodule size produced in the lime kiln could be a promising indirect method to measure the performance of the lime kiln. The objective of this investigation was to evaluate the utility of a laser triangulation camera for online monitoring of nodule size distribution for the lime kiln. A series of full-scale trials were performed in a lime kiln of a kraft pulp mill in which a camera was installed at the exit conveyor to analyze the lime discharging from the kiln. The nodule size distribution was analyzed for correlation with the lime temperature, flue gas temperature, and rotational speed of the kiln. The monitoring demonstrated temporal stability, and the results showed that the lime temperature had the most significant effect on the nodule size. The rotational speed of the lime kiln and the flue gas temperature showed limited effect on nodule size, but they had significant impact on the specific energy demand. The overall conclusion of the study is that the camera methodology effectively correlates lime temperature with nodule size distribution, and it advocates for the methods of implementation in automating lime temperature control, facilitating the production of consistently reactive lime at a lower specific energy consumption.

TEMPO/CaBr2/Ca(OCl)2 oxidation of hardwood bleached kraft pulp in water at pH 10 with aqueous Ca(OH)2 solution

The conventional TEMPO/NaBr/NaOCl system for oxidation of cellulose to prepare nanocellulose materials has some shortcomings in terms of controlling side reactions and clogging in washing/filtration process. A new TEMPO/CaBr2/Ca(OCl)2 system was then developed to oxidize a hardwood bleached kraft pulp (HBKP) in water at pH 10 (TEMPO = 2,2,6,6-tetramethylpiperidine-1-oxyl radical). An aqueous Ca(OH)2 solution was used to continuously control the reaction mixture at pH 10. After oxidation, the reaction mixture containing the oxidized products and chemicals was directly filtered on a 40-μm-mesh nylon filter and the water-insoluble oxidized products on the filter were washed with water without any clogging. The carboxy content increased to 1.5 mmol/g and the mass recovery ratio decreased to 87.7% as the amount of Ca(OCl)2 was increased to 10.0 mmol/g-HBKP. The oxidized products contained calcium ions but almost no chloride ions, indicating that they comprised almost pure –(COO)2Ca groups. The ready filtration and washing of the oxidized products was probably owing to the low degree of dissociation of the –(COO)2Ca groups in water. The X-ray powder diffraction (XRD) and solid-state carbon 13 nuclear magnetic resonance (13C-NMR) analyses revealed that the crystallinities and crystal widths of the original cellulose I structure were mostly retained in the oxidized products. However, size-exclusion chromatography and viscosity analyses revealed that substantial depolymerization occurred on the cellulose and oxidized cellulose molecules in the products, as in TEMPO/NaBr/NaOCl-oxidized products.Graphical

A comparative study of the cell wall level delignification behaviour of four Nordic hardwoods during kraft pulping

Abstract Wood is a heterogeneous material with significant variation among species. This inherent complexity poses a challenge to the continuous expansion of our understanding of the kraft process; yet previous pulping research has mainly been limited to a few species. This study investigates variations among some less studied species and their cell wall level delignification behaviour during kraft pulping. Ground wood of birch, beech, aspen, and alder were pulped at near-constant composition and temperature conditions. Minor, yet significant, differences in the rates of their delignification were observed: aspen had a pronounced fast rate during the initial stage, whereas alder delignified more slowly relative to its high initial lignin content. The dissolution of xylan was substantially faster for birch. In contrast, no substantial differences were detected between the species in the molecular weight and structure of the dissolved wood components, suggesting that the different delignification behaviours stem from variations in the residual phase. The molecular weight distribution of dissolved lignin was uniform during the initial stage of pulping, which is indicative of rapid and extensive fragmentation. Subsequently, the weight increased continuously for the remainder of the process, suggesting that the mass transfer within the cell wall influenced the overall delignification kinetics.

Understanding the potential of bamboo fibers in the USA: A comprehensive techno‐economic comparison of bamboo fiber production through mechanical and chemical processes

AbstractThe growing interest in bamboo fibers for pulp, paper, and board production in the USA necessitates a comprehensive financial viability assessment. This study conducts a detailed technoeconomic analysis (TEA) of bamboo fiber production, primarily for the consumer hygiene tissue market although it is also applicable to other industrial uses. The economic viability of two pulping methods – alkaline peroxide mechanical pulping (APMP) and ammonium bisulfite chemical pulping (ABS) – was explored within three different pulp mill settings to supply pulp to two nonintegrated tissue and towel mills in South Carolina, USA. The target was to produce wet lap bamboo bleached pulp at 50% consistency and 70% ISO brightness. Despite higher initial capital invesment and operating costs, ABS achieved a lower minimum required selling price – USD 544 to 686 per bone dry metric ton (BDt = 1000 BDkg) – in comparison with USD 766 to 899 BDt−1 for APMP. This price advantage is partly due to an additional revenue stream (lignosulfonate byproduct), which not only boosts revenue but also circumvents the need for expensive chemical recovery systems. When compared with traditional kraft pulping, both methods require significantly lower capital investments, with minimum required selling prices (estimated to achieve 16% IRR) below current market rates for extensively used bleached kraft pulps in the USA tissue industry. The economic benefits derive from several factors: the low cost of bamboo as raw material, reduced capital needs for new pulping technologies, lower transportation costs from the pulp mill to tissue and towel manufacturing facilities, and the high market price of bleached kraft pulp.

Foam-laid extensible paper for improved extensibility and press-forming performance

This study was motivated by the recent raising interest for the sustainable plastic-free dry 3D formable materials. 3D forming processes are capable to produce large unit quantities, but the process conditions for packaging applications have been typically very demanding for cellulose-based materials. This study covers some of the key factors affecting the extensibility of cellulose fibre-based materials and presents a laboratory-scale development study of a press-formable material concept. The investigation focused on comparisons of two refining concepts for bleached softwood kraft (BSK) pulp and two sheet forming concepts, namely water-laid and foam-laid forming. Additionally, influence of thermoplastic additives on the extensibility and 3D forming performance were investigated. In-plane compaction was applied with Expanda® laboratory device. Performance of the materials was evaluated by tensile tests and depth of the 3D formed shapes. In this study, in-plane compaction at first in cross-machine direction (CD) and then in machine direction (MD) led to over 30% elongation with BSK-based laboratory sheets containing latex as a binder and foaming agent. In addition to high elongation, optimal strength was needed for the best press-forming performances. In-plane compaction was the most significant factor regarding the elongation, but it also decreased the strength of the materials. Similar press-forming performance was found with two materials with either highly anisotropic or more isotropic elongation. The elongation anisotropy was created by one-way and two-way in-plane compactions. The results indicate that a reasonable performance for BSK-based materials for 3D forming applications can be reached using the presented concept.

Removal, accumulation, and micro-ecosystem impacts of typical POPs in bioretention systems with different media: A runoff infiltration study

Bioretention systems prove effective in purifying common persistent organic pollutants (POPs) found in urban rainfall runoff. However, the response process of the microecosystem in the media becomes unclear when POPs accumulate in bioretention systems. In this study, we constructed bioretention systems and conducted simulated rainfall tests to elucidate the evolution of micro-ecosystems within the media under typical POPs pollution. The results showed all POPs in runoff were effectively removed by surface adsorption in different media, with load reduction rates of >85 % for PCBs and OCPs and > 80 % for PAHs. Bioretention soil media (BSM) + water treatment residuals (WTR) media exhibited greater stability in response to POPs contamination compared to BSM and pure soil (PS) media. POPs contamination significantly impacted the microecology of the media, reducing the number of microbial species by >52.6 % and reducing diversity by >27.6 % at the peak of their accumulation. Enzyme activities were significantly inhibited, with reductions ranging from 44.42 % to 60.33 %. Meanwhile, in terms of ecological functions, the metabolism of exogenous carbon sources significantly increased (p < 0.05), while nitrogen and sulfur cycling processes were suppressed. Microbial diversity and enzyme activities showed some recovery during the dissipation of POPs but did not reach the level observed before the experiment. Dominant bacterial species and abundance changed significantly during the experiment. Proteobacteria were suppressed, but remained the dominant phylum (all relative abundances >41 %). Bacteroidota, Firmicutes, and Actinobacteria adapted well to the contamination. Pseudomonas, a typical POPs-degrading bacterium, displayed a positive correlation between its relative abundance and POPs levels (mean > 10 %). Additionally, POPs and media properties, including TN and pH, are crucial factors that collectively shape the microbial community. This study provides new insights into the impacts of POPs contamination on the microbial community of the media, which can improve media design and operation efficiency.

Data-driven modeling and multi-objective optimization of a continuous kraft pulping digester

Understanding wood characteristics is essential for enhancing the economic sustainability of the kraft process. In a recent work, we included wood characteristics in the phenomenological modeling of digesters. The developed model allows the optimization of the process. Here, we propose a constrained multi-objective optimization approach to minimize the residual lignin content while maximizing the carbohydrate content in the cellulose pulp, using the Non-dominated Sorting Genetic Algorithm II. In order to reduce computational costs during the optimization, we developed a surrogate model, based on simulated data, to predict key performance indicators. We evaluated two machine learning techniques: Multilayer Perceptron (MLP) and decision tree-based methods, considering single and multiple outputs. The combination between the multiple-output approach and MLP performed well and resulted in a more simplified surrogate model. The results for the simulation and the surrogate model were similar, and the computational cost was approximately 50 times lower for the surrogate model. An uncertainty was associated with the multiplicative factor of the delignification rate as a way to observe how its estimate interferes with the Pareto curve. The present work presents contributions to data-driven modeling and multi-objective optimization of digesters, allowing us to determine the importance of wood characteristics in operation.

Identification and time evolution of thionyl chloride (SOCl2) radiolysis products

Abstract Innovative solutions are needed to reduce the amount of high-level waste generated by used nuclear fuel recycling strategies to support the widespread adoption of sustainable nuclear fission energy technologies. To this end, a new sulfur chloride-based process has been developed to recycle zirconium alloy-based materials, which make up a significant fraction of high-level radioactive waste. To support the continued development of this process, we present new data on the potential reaction pathways over time of the products arising from the gamma and electron beam radiolysis of neat thionyl chloride (SOCl2). Interrogation of the gamma irradiated liquid by Raman spectroscopy provided more conclusive identification of the SOCl2 degradation products, specifically sulfur dichloride (SCl2), molecular chlorine (Cl2), sulfur dioxide (SO2), and sulfuryl chloride (SO2Cl2). In comparison, the high dose rate (∼107 Gy s−1) electron beam irradiations formed significantly more degradation products. For both cobalt-60 gamma and electron beam irradiations, the observed degradation products were found to evolve as a function of time post-irradiation via the same reaction pathways, with indication of a solvent regeneration mechanism. These findings are fortuitous for process development, as such a mechanism would be beneficial for process longevity and cost effectiveness.

Statistical estimation of the early to middle Ediacaran ocean redox architecture in the Yangtze block of South China

Early to middle Ediacaran organic-rich black shales host several famous fossil biotas and provide key evidence for understanding the coevolution of multicellular organisms and palaeoceanic environment. The water column redox states play critical roles in organic-rich shale deposition. Amongst multiple geochemical redox indexes, iron-speciation chemistry (FeHR/FeT, Fepy/FeHR) in shales constitutes a reliable proxy to reconstruct the first-order redox framework of the ocean basin. However, iron-speciation is a local marine redox proxy, and only compiled data collected from multiple different sedimentary facies record statistically significant changes of oxidation states within a depositional basin. Here we compiled the spatiotemporal distribution of iron-speciation data in early to middle Ediacaran black shales of the Yangtze block in South China. New high-resolution analysis on two outcrops and one drill-core reflects overall ferruginous condition and dominant euxinic condition locally interrupted by oxic states, respectively, generally indicating pervasive anoxic depositional environment for the Member II shales of the Ediacaran Doushantuo Formation in the Lower Yangtze block. Compilation of fourteen Ediacaran sections from shallow-, slope- and deep-water facies demonstrates frequent spatiotemporal oscillation of the redox conditions throughout the Yangtze block. Widespread ferruginous states, accompanied with euxinic zones mainly focusing in lower slope facies, are detected during the early Ediacaran period, in contrast with more widespread euxinic settings in the middle Ediacaran period. Statistical data including new high-resolution results from the Lower Yangtze block show generally low enrichment for redox sensitive elements (RSEs, e.g., Mo, V and U) in the Member II shales probably due to their contemporary low seawater concentrations. An increase of RSEs concentrations occurs in the Member IV shales, which probably reflects more oxidized Earth surface environment during middle Ediacaran period. The increasing Earth oxygenation documents the occurrence of widespread euxinic states during deposition of the Member IV shales. Compilation of spatial distribution of TOC contents in black shales demonstrates their apparent relevance to spatial distribution of the euxinic rather than ferruginous states, which is likely due to the favorable role of sulfurization process on burial and preservation of organic matters. The euxinic states may also facilitate the exceptional preservation of the soft-bodied Ediacaran fossils.

Research on semi-supervised soft sensor modeling method for sulfur recovery unit based on ISSA-VMD-ESN

Sulfur recovery unit (SRU) in the refining industry can effectively reduce sulfide emissions and achieve efficient use of resources. Predicting sulfide emissions with soft sensors can provide the basis for process optimization and control, to improve SRU’s stability and efficiency. However, due to the dynamicity and nonlinearity of the sulfur recovery process, existing soft sensor models have poor prediction accuracy. Therefore, this paper proposes a semi-supervised soft sensor modeling method based on variational mode decomposition (VMD), echo state network (ESN) and improved sparrow search algorithm (ISSA). Firstly, Reconstructing SRU dataset using semi-supervised fusion method to reduce the impact of dynamicity on prediction results. Secondly, through the ISSA to optimize the VMD parameters and using the optimized VMD to decompose the output sequences into multiple components, to reduce the nonlinearity of sequences. Then, the soft sensor modeling of each component using ESN. Additionally, the ESN parameters are optimized by ISSA to prevent the effect of improper parameter settings on the model’s prediction performance. Afterwards, the predicted values of each component are superimposed to obtain the final prediction. Finally, simulation experiments are conducted based on the SRU dataset of an oil refinery to verify the effectiveness and generalization of the proposed method.

Enhancing subsequent kraft fiber dewatering properties by using fiber polyamide-epichlorohydrin (PAE) treatment to prepare a dry pulp product,

The energy needed for the dewatering and drying of wet paper web represents around half of the energy consumption of papermaking processes. The present work examined whether the dewatering and drying of paper could be enhanced during a previous pulp drying process by pretreating the fibers with polyamide-epichlorohydrin (PAE). According to the hypothesis, the cured PAE restrains swelling and water absorption of water-wetted fibers by forming a fiber-bound, self-crosslinked polymer-network on the fiber surfaces. The hypothesis was tested by adding PAE to never-dried kraft pulp slurry followed by pulp thickening, drying, and final curing of the PAE-resin. After this, the PAE-treated fibers were dispersed in water, and their water retention values (WRV) and Shopper-Riegler values (○SR) were measured. The PAE pretreatments notably decreased the fibers´ WRV and ○SR, indicating improved water removal of paper web in the paper machine forming and drying section. Compared to chemical crosslinking pretreatments, which also can be used to decrease fibers WRV and ○SR-value, a notable advantage of PAE-pretreatment is milder required curing conditions of the PAE, which makes implementation of the method easier in practice. Due to decreased fiber-to-fiber bonding capability, the PAE-treated specialty fibers could take advantage especially as a bulking aid of paperboard, tissue, and absorbent materials.

Sulfur isotopes from the Paleoproterozoic Francevillian Basin record multigenerational pyrite formation, not depositional conditions

Bulk-rock sulfur isotope data from pyrite in the ~2.1 billion-year sedimentary rocks of the Francevillian Basin, Gabon, have underpinned ideas about initial oxygenation of Earth’s surface environments and eukaryote evolution. Here, we show, using micro-scale analytical methods, that the bulk sulfur isotope record represents progressive diagenetic modification. Our findings indicate no significant change in microbial sulfur cycling processes and seawater sulfate composition throughout that initial phase of atmosphere-ocean oxygenation of Paleoproterozoic time. This offers an alternative view of Earth system evolution during the transition from an anoxic to an oxic state and highlights the need for a judicious reappraisal of conceptual models using sulfur isotope data as primary depositional signals linked to global-scale biogeochemical processes.

Silver-Doped Titanium Oxide Layers for Improved Photocatalytic Activity and Antibacterial Properties of Titanium Implants.

Titanium has a long history of clinical use, but the naturally forming oxide is not ideal for bacterial resistance. Anodization processes can modify the crystallinity, surface topography, and surface chemistry of titanium oxides. Anatase, rutile, and mixed phase oxides are known to exhibit photocatalytic activity (PCA)-driven bacterial resistance under UVA irradiation. Silver additions are reported to enhance PCA and reduce bacterial attachment. This study investigated the effects of silver-doping additions to three established anodization processes. Silver doping showed no significant influence on oxide crystallinity, surface topography, or surface wettability. Oxides from a sulfuric acid anodization process exhibited significantly enhanced PCA after silver doping, but silver-doped oxides produced from phosphoric-acid-containing electrolytes did not. Staphylococcus aureus attachment was also assessed under dark and UVA-irradiated conditions on each oxide. Each oxide exhibited a photocatalytic antimicrobial effect as indicated by significantly decreased bacterial attachment under UVA irradiation compared to dark conditions. However, only the phosphorus-doped mixed anatase and rutile phase oxide exhibited an additional significant reduction in bacteria attachment under UVA irradiation as a result of silver doping. The antimicrobial success of this oxide was attributed to the combination of the mixed phase oxide and higher silver-doping uptake levels.

1-Ethyl-3-methylimidazolium Acetate as a Reactive Solvent for Elemental Sulfur and Poly(sulfur nitride).

We investigate the reactive dissolution process of poly(sulfur nitride) (SN)x in the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate [EMIm][OAc] in comparison to the process of elemental sulfur in the same IL. It has been known from the literature that during the reaction of S8 with [EMIm][OAc], the respective thione is formed via a radical mechanism. Here, we present new results on the kinetics of the formation of the respective imidazole thione (EMImS) via the hexasulfur dianion [S6]2- and the trisulfur radical anion [S3]•-. We can show that [S6]2- is formed first, which dissociates then to [S3]•-. Also, long-term stable radicals occur, which are necessary side products provided in a reaction scheme. During the reaction of [EMIm][OAc] with (SN)x chains, two further products can be identified, one of which is the corresponding imine. The reactions are followed by time-resolved NMR spectroscopic methods that showed the corresponding product distributions and allowed the assignment of the individual signals. In addition, continuous-wave (CW) EPR and UV/vis spectroscopic measurements show the course of the reactions. Another significant difference in both reactions is the formation of a long-term stable radical in the sulfur-IL system, which remains active over 35 days, while for the (SN)x-IL system, we can determine a radical species only with the spin trap 5,5-dimethyl-1-pyrrolin-N-oxide, which indicates the existence of short-living radicals. Since the molecular dynamics are restricted based on the EPR spectra, these radicals must be large.

Process Design for Direct Production of Battery Grade Nickel Sulfate

The clean energy transition has increased the global demand of nickel sulfate used in the Li-ion batteries. A short-term solution is to refine the nickel sulfate product from nickel intermediates. In the long-term, new direct nickel sulfate production technologies are needed. This research focused on the modeling-based concept development of a novel direct hydrometallurgical nickel sulfate process consisting of chemical leaching, impurity removal by precipitation, solvent extraction, and crystallization as an alternative to the conventional nickel sulfate production route via a nickel matte intermediate. The conventional process route with the studied nickel concentrate had lower chemical consumption and waste production compared to direct hydrometallurgical process where approximately 60% of iron was leached consuming oxygen, and the following iron precipitation step consuming calcium carbonate resulted in a high amount of iron precipitate together with gypsum. However, hydrometallurgical alternatives are often suitable for lower ore grades or volumes and can recover copper as by-product metal. The biggest impacts on carbon footprint from chemical consumption in the direct hydrometallurgical process were generated in iron precipitation and oxygen use in leaching. With the studied nickel concentrate, pyrrhotite played a key role in both oxygen use and iron precipitation. In the leaching step, 68% of total oxygen consumption was related to pyrrhotite leaching, while in iron removal 73% of total iron originated from pyrrhotite. Thus, especially pyrrhotite removal prior to leaching needs to be developed to reduce the carbon dioxide footprint, when the pyrrhotite content in the material is high.Graphical

Rational Design of Phase-Engineered WS2/WSe2 Heterostructures by Low-Temperature Plasma-Assisted Sulfurization and Selenization toward Enhanced HER Performance.

Efficient hydrogen generation from water splitting underpins chemistry to realize hydrogen economy. The electrocatalytic activity can be effectively modified by two-dimensional (2D) heterostructures, which offer great flexibility. Furthermore, they are useful in enhancing the exposure of the active sites for the hydrogen evolution reaction. Although the 1T-metallic phase of the transition metal dichalcogenides (TMDs) is important for the hydrogen evolution reaction (HER) catalyst, its practical application has not yet been much utilized because of the lack of stability of the 1T phase. Here, we introduce a novel approach to create a 1T-WS2/1T-WSe2 heterostructure using a low-temperature plasma-assisted chemical vapor reaction (PACVR), namely plasma-assisted sulfurization and plasma-assisted selenization processes. This heterostructure exhibits superior electrocatalytic performance due to the presence of the metallic 1T phase and the beneficial synergistic effect at the interface, which is attributed to the transfer of electrons from the underlying WS2 layer to the overlying WSe2 layer. The WS2/WSe2 heterostructure catalyst demonstrates remarkable performance in the HER as evidenced by its small Tafel slope of 57 mV dec-1 and exceptional durability. The usage of plasma helps in replacing the top S atoms with Se atoms, and this ion bombardment also increases the roughness of the thin film, thus adding another factor to enhance the HER performance. This plasma-synthesized low-temperature metallic-phase heterostructure brings out a novel method for the discovery of other catalysts.

Refinability of mercerized softwood kraft pulp

In this study, the impact of mercerization and PFI refining on the properties of softwood kraft pulp was investigated. Never-dried softwood kraft pulp was treated with 15 wt% NaOH to generate highly hydrated fibers, followed by PFI refining to increase pulp fibrillation and porosity. The original and modified pulp properties were assessed for morphological and chemical composition. Differential scanning calorimetry (DSC) tests and water retention value (WRV) measurements were conducted to evaluate pulp swelling behavior and porosity. Fiber bonding potential and strength properties were evaluated from handsheets of mercerized and unmercerized pulp. Mercerization with 15 wt% NaOH successfully converted cellulose I to cellulose II, leading to slightly increased pulp swelling and micropore volume. However, the mercerization reduced handsheet strength properties. Furthermore, PFI refining resulted in a negligible enhancement of bonding in mercerized pulp, in stark contrast to its significant effect on unmercerized kraft pulp.

Mirror Plane Effect of Magnetoplumbite-Type Oxide Restraining Long-Chain Polysulfides Disproportionation for High Loading Lithium Sulfur Batteries.

A facile solid-state approach is employed to synthesize a novel magnetoplumbite-type oxide of NdMgAl11O19, which integrates spinel-stacking layers (MgAl2O4) with Nd-O6 mirror plane structures. The resulting NdMgAl11O19 exhibits remarkable catalytic activity and conversion efficiency during the sulfur reduction reaction (SRR) in lithium-sulfur batteries. By employing the 2D projection mapping technique of in situ confocal Raman spectroscopy and electrochemical technique, it is discovered that the exposed mirror plane structure of Nd-O6 can effectively suppress the undesiring disproportionation reaction (S8 2-→S6 2-+1/4 S8) of long-chain lithium polysulfides at the initial stages of sulfur reduction, thereby promoting the positive process of sulfur to lithium sulfide. This not only mitigates the issue of sulfur shuttle loss but also significantly improve the kinetics of the conversion process. Leveraging these advantages, the NdMgAl11O19/S cathode delivered an impressive initial capacity of up to 1398 mAh g-1 at an electrolyte/sulfur (E/S) ratio of 5.1µL mg-1 and a sulfur loading of 2.3mg cm-2. Even when the sulfur loading is increased to 10.02mg cm-2, the cathode retained a reversible areal capacity of 10.01 mAh cm-2 after 200 cycles. This mirror engineering strategy provides valuable and universal insights into enhancing the efficiency of cathodes in Li-S battery.

Influence of Soda and Kraft lignin in polyurethane coatings for the corrosion protection of mild steel in 3.5 % NaCl solution

This study highlights the potential of coconut shell biomass waste-derived lignins (CSL) as corrosion inhibitors to reinforce the coating properties of polyurethane. The utilization of CSL involves a green approach to prepare eco-friendly metallic coatings. Herein, lignin was extracted via Kraft and Soda pulping processes. The present findings indicated that the percentage yield of Soda lignin (SL) (26.43 ± 0.75 %) was significantly higher than that of Kraft lignin (KL) (8.52 ± 0.39 %). Electrochemical impedance spectroscopy and potentiodynamic polarization corrosion monitoring techniques were used to evaluate the anticorrosive performance of modified polyurethane coatings on mild steel exposed to 3.5 % NaCl solution. In this study, doping concentration of 5 wt% KL and SL into polyurethane attained the optimum anticorrosion performance. The surface conditions of uncoated and coated mild steel substrates were investigated through scanning electron microscopy/energy dispersive X-ray (EDX) analysis, salt spray and adhesion tests. EDX analysis demonstrated that polyurethane added with 5 wt% doping concentration of SL contained the highest content of Fe (86.05 wt%) compared to 5 wt% KL which contained 79.64 wt% of Fe, whereas neat polyurethane coating contained 75.43 wt% of Fe. Hence, enhanced corrosion protection of polyurethane through the addition of CSL, particularly SL, possesses a viable and an effective green approach to utilize coconut shell biomass waste for the application as a potential corrosion inhibitor in organic coatings.

Effects of optically inert ions on up-conversion luminescence and temperature-sensing properties of Y2O2S: Er3+/Yb3+/Tm3+ phosphors

The quenching of luminescence in Er3+/Yb3+ co-doped with Tm3+ presents a dilemma as it substantially diminishes thermometric performance. In this study, Y2O2S: Er3+/Yb3+/Tm3+ phosphors were synthesized using a homogeneous precipitation method combined with a sulfurization process. In addition, three sets of fluorescence intensity ratio (FIR) models were designed, which have self-calibration function. The effects of incorporation of Li+ or Li+/Ba2+ on the up-conversion luminescence (UCL) intensity and thermometric performance of the phosphors were systematically studied. The results show that the introduction of Li+ or Li+/Ba2+ co-doping leads to lattice distortion and the formation of oxygen ion vacancies in the lattice, which further accelerates the energy transfer process and mixes the charge transfer states, and ultimately dramatically improves the UCL and thermometric performance. The introduction of Li+ and Li+/Ba2+ co-doping enhanced the UCL of the materials by about 3.7 times and 5.6 times compared to Y2O2S: Er3+/Yb3+/Tm3+. When based on nonthermally coupled levels (NTCLs), the Sr-max of Li+/Ba2+ co-doped sample is 0.080 K−1 at 573 K, which is 87 % higher than that based on TCLs. These findings not only provide a new avenue for improving the UCL and thermometric performance but also provide an accurate self-calibration FIR model over a wide temperature range.