Commercial Pigments Research Articles

Blue Na2O - CoO - P2O5 glasses: Structural, physico-chemical, thermal and optical characterizations

Two blue phosphate glasses series, (50-x/2)Na2O - xCoO - (50-x/2)P2O5 (0 ≤ x ≤ 35) and (50-x)Na2O - xCoO - 50P2O5 (0 ≤ x ≤ 50) labelled NaCoPO(I) and NaCoPO(II), were synthesized by the melt quenching route and characterized by diverse techniques. Introduction of cobalt oxide CoO in vitreous NaPO3 metaphosphate induces an increase in the glass transition temperature, a decrease in the molar volume and the dissolution rate of the glasses in distilled water, and therefore a strengthening of the glass network. Raman spectra of NaCoPO(I) series, where O/P ratio varies from 3 to 3.54, show that Co2+ ions breakdown the infinite metaphosphate chains and provoke remarkable structural modifications. In contrast, no significant change was observed in the glassy network of NaCoPO(II) series, where O/P ratio is constant and equal to 3. Optical study results show that Co2+ ions have both octahedral and tetrahedral environments with predominance of tetrahedral coordination. The reduction in band gap energy when CoO content rises is due to the increase of non-bridging oxygen number in the vitreous network. The values of CIE L∗a∗b∗ parameters are consistent with the blue color, sought for commercial pigments. The physical parameters deduced from optical spectra suggest that the studied glasses are promising materials for several applications such as pigments and nonlinear optical materials.

Upcycling process of mill scale waste into high-value ceramic products

Ceramic industry consumes large amounts of raw materials, including costly and environmental impact iron based-pigments. Steel rolling (SR) and wire drawing (WD) waste, rich in iron (>67 wt %), present a viable alternative. This study aims to develop high value stoneware pastes for tableware products by substituting commercial pigments with SR and WD. The influence of incorporation content (3, 5 and 10 wt %) and pre-treatments (sieving at 250, 150 and 63 μm, and grinding followed by sieving at 63 μm) on the samples properties was assessed including weight loss, firing shrinkage, apparent density, flexural resistance, and water absorption. The laboratory scale results revealed that darker hues, ranging from grey to reddish, were obtained when SR and WD were incorporated in the stoneware paste (beige colour). The smaller the particle size, more homogeneous is the developed colour, which is intensified as higher is the incorporation level.The prototypes (plates) were characterized in terms of thermal shock, edge impact, cracking and microwaves resistance, water absorption, and leaching behaviour, demonstrating that they met the industrial requirements. Thermal shock resistance was enhanced and the levels of leached Fe, Pb, Cd, Ni, Cr, Mo, V, Zn, and Cu, were below permissible limits (EU Ceramic Directive 84/500/EEC, Decree-Law n°152/2017, Decree-Law n°236/98 and WHO Guidelines for Drinking-Water Quality) confirming their effective immobilization. Concluding, this work shows the viability of using mill scale waste as a valuable secondary raw material in stoneware pastes acting as a chromophore agent. Dark colours are obtained while preserving the product technical characteristics, promoting sustainable production and reducing landfilled waste.

Valorisation of Metallurgical Waste for Inorganic Pigments Production

AbstractFour industrial wastes, namely, tionite (T), iron grit (IG), electroplating sludge (ES), and mill scale (MS), are typically disposed of in controlled hazardous landfills because of their toxic content, posing potential harm to human health and to the environment. At the same time, the chemical composition of these wastes, specifically the nature and content of transition metals, makes them potentially attractive for reuse in pigments manufacturing. This work details the study of these residues for producing coloured perovskites to be tested as inorganic pigments. The residues were mixed, in different proportions, and subsequently calcined to produce the required structures. The colouring potential was then assessed in a ceramic paste and in a transparent glaze. Leaching tests were carried out to verify the effective immobilisation of the hazardous species. Dark pigments were successfully obtained from the mixtures of T: ES: Co3O4, T: MS and T: IG. The crystalline phases present in T: ES: Co3O4 are nickel–chromium iron oxide spinel–Fe1.5Cr0.5NiO4 (without Co) or trevorite–Fe2NiO4 (with Co), titanium nickel oxide–TiNiO3 and titanite–CaTiSiO5. The mixtures T: MS and T: IG presented hematite (Fe2O3) and pseudobrookite (Fe2TiO5). Leaching tests confirmed the non-hazardous or inert character of the synthesized pigments. Products showed brownish or greyish hues, depending on the pigment added. T:75ES_1100, T:73ES:2Co_1100, T:75MS_1000, T:75MS_1100 and T:75IG_1000 pigments can effectively and safely be used to colour ceramic paste replacing partially or totally the commercial pigments.

Environmental friendly multifunctional orange pigment for cool coating applications

The present study illustrates the development of an environmentally benign intense orange inorganic pigment, by substituting Si4+ metal ion at the Bi3+ site of Bi4V2O11 via solid-state method. The partial replacement of Si4+, induced a strain in the crystal lattice of the compound, which resulted in a substantial improvement in the visible light reflectance. A reduction in oxygen deficiency in the lattice structure facilitated the colour tuning of the pigment series from brownish red to orange and then on to yellowish orange. The composition Bi3.8Si0.2V2O11+δ exhibited a bright orange hue with colour co-ordinates a* = 39, b* = 34 and L* = 52. Furthermore, NIR solar reflectance of the pigment was 86%, which is superior than the reported and commercial orange pigments. Compared to commercial pigment coatings, Bi3.8Si0.2V2O11+δ achieved a temperature reduction of 2 °C inside a foam model house. An exceptional corrosion resistance of 1.6 × 1010 Ωcm2, was registered by the pigment loaded epoxy coating with good stability. The corrosion inhibition mechanism of the pigment operates through the hand in hand working of passive Bi-O and Si-O, active FeOOH and vanadate moiety. On the whole, the new multifunctional orange pigment has the potential to be a viable replacement for the toxic commercial pigments in the market.

Ultramarine blue pigment degradation in cementitious materials: a new approach to the phenomenon

The paper analyses the degradation process of commercial ultramarine blue pigments in cementitious materials. For this purpose, two commercial pigments (with and without a protective coating) in different solutions and cement pastes are studied incrementally. The results show that pigment degradation occurs due to an ion exchange phenomenon; during hydration high ion contents are released, calcium and potassium being the most aggressive for the pigment. Calcium distorts the unit cell; between the sodium of the pigment and the potassium in the medium a cation exchange phenomenon takes place. Both processes lead to the diffusion of sulphate and sulphide ions from the pigment to the medium causing loss of colour and the formation of ettringite.

Development of Decorative Mortars with Pigments from Acid Mine Drainage: Analysis of Physical and Mechanical Properties

The construction industry is recognized for its high consumption of natural resources, resulting in significant environmental impacts. Given this reality, it is essential to seek new methods and solutions that minimize the impact of this activity on the environment. An innovative approach consists of using pigments derived from acid mine drainage (AMD) as a sustainable alternative in the production of mortar for decorative façade cladding. In this context, the main objective of this paper was to evaluate the physical/mechanical properties of decorative mortars developed by partially replacing natural sand with pigment from acid mine drainage. Initially, the pigment (yellow) was produced, characterized, and compared with a commercial pigment. Sequentially, decorative mortars were developed with different pigment concentrations (0%, 2%, 4%, and 6%). The mortars were subjected to compressive strength, flexural tensile strength, shrinkage, loss of mass, and colorimetry tests. The results showed that compressive strength, flexural tensile strength, weight loss, and dimensional variation were significantly affected by the partial addition of pigment to replace natural aggregate. In other words, there was a decrease in strength and an increase in mass loss and expansion of the mortars. However, the main factor influencing these variables was the greater amount of water added in the higher substitution cases. The addition of water was necessary to keep the consistency constant. A possible solution to maintain the same amount of water and avoid negative effects on the mortar properties would be to use additives in the mortar formulation in future work. Therefore, this research contributes to the search for more sustainable solutions in civil construction, exploring the use of pigments from AMD as a viable alternative to reduce the environmental impacts associated with this industry.

Cost-effective pearlescent pigments with high near-infrared reflectance and outstanding energy-saving ability for mitigating urban heat island effect

Cooling down the surface temperature of buildings and saving energy consumption are tasks of top priority in mitigating the urban heat island (UHI) effect. The bright and colorful pearlescent pigmented cool coatings with high near-infrared (NIR) reflectance possess promise in enhancing the reflective effect of solar light and the visual aspect, which is still an undeveloped domain. Herein, these novel solar reflective coatings containing mediums and pearlescent pigments with high NIR reflectance of 85% embodied obvious energy-saving effects on building materials. EnergyPlus software was used to simulate the energy-saving effect of four applied climate zones, including New York, Nanchang, Lima, and Brasilia. Compared to commercial pigments (Fe2O3, γ-Ce2S3) with similar colors, the RK 402 and RK 301 pearlescent pigments demonstrate superior energy-saving capabilities in Nanchang climate zone, and can save 1.00 kW h m−2 and 1.60 kW h m−2 annually, respectively. In the warmer climate zone of Brasilia, the highest energy-saving efficiency is 2.06 kW h m−2 over one year by RK 301 pearlescent pigment. After irradiated by an NIR lamp, the surface temperature of the RK 301 coating can be reduced by 34.8 °C compared with that of the Fe2O3 commercial coating, and that of RK 402 coating is 5.2 °C compared with the γ-Ce2S3 commercial coating. Furthermore, the 7-day field test also has consistent effect of cooling down the surface temperature. This work demonstrated that pearlescent coatings with brilliant colors have great potential for application as cold materials in building areas to mitigate the UHI effect.

Simplified hydrometallurgical route for the synthesis of silica-free hematite from iron ore tailings

The processing of iron ore generates large volumes of tailings. Acid leaching enables the solubilization of iron in an aqueous solution, allowing the production of ferric liquor and a silica-rich residue. The purpose of this investigation was to use the leachate resulting from this process to synthesise high-quality iron oxide. The conducted methodology involved acid leaching, selective iron precipitation as a function of pH, and the thermal conversion of the precipitated iron oxy-hydroxides into iron oxide particles. The iron oxide consisted of micro/nano Fe2O3 particles which were free of silica, with iron contents of 64% and particle sizes of less than 28 μm. The process presented an overall iron recovery around 84%. The resulting material could be used as a commercial pigment or be incorporated into steel-making iron pellets. The hydrometallurgical conversion of iron ore wastes into valuable products may contribute to the future of mining and to green steel production.

Microwave-Reactor-Based Preparation of Red Iron Oxide Pigment from Waste Iron Sulfate.

This article presents a two-step method of iron red synthesis based on waste long-term deposited iron(II) sulfate. The first step is the purification of waste iron sulfate, and then the pigment is synthesized by precipitation using a microwave reactor. The newly developed method of purification allows for quick and thorough purification of iron salt. The use of a microwave reactor in the synthesis of iron red makes it possible to reduce the temperature of the goethite-hematite phase transition from 500 °C to 170 °C and skip the calcination process. A temperature reduction in the synthesis decreases the formation of agglomerates of synthesized materials compared to commercial ones. The results of the research showed a change in the physicochemical properties of the obtained pigments depending on the conditions of synthesis. Waste iron(II) sulfate is a promising raw material for the synthesis of iron red pigments. Laboratory pigments are found to be differ from commercial pigments. The difference in properties speaks in favor of synthesized materials.

Microalgae-Derived Pigments for the Food Industry.

In the food industry, manufacturers and customers have paid more attention to natural pigments instead of the synthetic counterparts for their excellent coloring ability and healthy properties. Microalgae are proven as one of the major photosynthesizers of naturally derived commercial pigments, gaining higher value in the global food pigment market. Microalgae-derived pigments, especially chlorophylls, carotenoids and phycobiliproteins, have unique colors and molecular structures, respectively, and show different physiological activities and health effects in the human body. This review provides recent updates on characteristics, application fields, stability in production and extraction processes of chlorophylls, carotenoids and phycobiliproteins to standardize and analyze their commercial production from microalgae. Potential food commodities for the pigment as eco-friendly colorants, nutraceuticals, and antioxidants are summarized for the target products. Then, recent cultivation strategies, metabolic and genomic designs are presented for high pigment productivity. Technical bottlenecks of downstream processing are discussed for improved stability and bioaccessibility during production. The production strategies of microalgal pigments have been exploited to varying degrees, with some already being applied at scale while others remain at the laboratory level. Finally, some factors affecting their global market value and future prospects are proposed. The microalgae-derived pigments have great potential in the food industry due to their high nutritional value and competitive production cost.

Versatile strategy for homogeneous drying patterns of dispersed particles

After spilling coffee, a tell-tale stain is left by the drying droplet. This universal phenomenon, known as the coffee ring effect, is observed independent of the dispersed material. However, for many technological processes such as coating techniques and ink-jet printing a uniform particle deposition is required and the coffee ring effect is a major drawback. Here, we present a simple and versatile strategy to achieve homogeneous drying patterns using surface-modified particle dispersions. High-molecular weight surface-active polymers that physisorb onto the particle surfaces provide enhanced steric stabilization and prevent accumulation and pinning at the droplet edge. In addition, in the absence of free polymer in the dispersion, the surface modification strongly enhances the particle adsorption to the air/liquid interface, where they experience a thermal Marangoni backflow towards the apex of the drop, leading to uniform particle deposition after drying. The method is independent of particle shape and applicable to a variety of commercial pigment particles and different dispersion media, demonstrating the practicality of this work for everyday processes.

Spatial distribution, sources identification, and health risk assessment polycyclic aromatic hydrocarbon compounds and polychlorinated biphenyl compounds in total suspended particulates (TSP) in the air of South Pars Industrial region-Iran.

South Pars Industrial Energy Zone, located in the southwest of Iran along the Persian Gulf coast, encompasses many industrial units in the vicinity of urban areas. This research study investigated the effects of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) on human health and the environment. Suspended particulate matters (SPM) in the air sampled, in summer and winter 2019, from ten stations next to industrial units and residential areas. The samples were analyzed by gas chromatography-mass spectrometry (GC-MS). Spatial distribution maps of pollutants in the region were prepared using GIS software. The highest carcinogenic risk due to PAHs and PCBs measured as ([Formula: see text]) and ([Formula: see text], respectively. According to the US Environmental Protection Agency limit ([Formula: see text]), the cancer risks from PAH compounds were significant and need further investigation. The PCB cancer risks were within acceptable ranges. The highest adsorption ratios for PAHs were obtained through skin and PCBs by ingestion. The maximum measured non-carcinogenic hazard indexes (HI) turned out to be 0.037 and 0.023 for PAH and PCB, respectively, and were reported as acceptable risks. The predominant source of PAH in industrial areas was liquid fossil combustion, and in urban areas replaced by coal-wood-sugarcane combustion. Petrochemical complexes, flares, power plants (69%), electric waste disposal sites, and commercial pigments (31%) were reported as PCB sources. Industries activities were the most effective factors in producing the highest level of carcinogenic compounds in the region, and it is necessary to include essential measures in the reform programs.

Synthesis, spectroscopic and physico-chemical studies of novel pigments derived from Lithol Rubine

PurposeThe pursuit of manufacturing new inks with low financial cost is an urgent economic demand. Thus, the purpose of this paper is to synthesize some new pigments derived from Lithol Rubine (LR) via a successful simple route and to investigate their physicochemical properties for usage in the inks industry.Design/methodology/approachTwo novel pigments were generated during the reaction of LR with Mn(II) and Co(II) salts in ethanolic solutions. The obtained pigments were isolated as solid compounds and characterized through elemental analysis, UV–vis, Fourier transform infrared, 1H NMR spectra, oil absorption, specific gravity, melting point, molar conductivity and magnetic moment measurements. Their dyeing and durability characteristics were examined using American Standard Testing Methods. The synthesized pigments were then applied in inks formulation.FindingsThe printing inks containing the two new pigments (LR–Mn and LR–Co) were compared to (GF 59-606 and GF 59-616), respectively. The results of this study showed that the performance of newly prepared pigments was comparable to that of commercial pigments currently in use in the inks industry.Practical implicationsLR and its new derivative pigments can be used in other different applications such as paper coating, crayon, rubber and paint industries.Originality/valueThe authors designed an efficient synthesis for some novel pigments. The synthesis technique is featured by a short reaction time, high yields and ease of use. The pigments developed would be good and cost-effective substitute for the original commercially available and expensive pigments used in the inks industry.

Synthesis of Indigo-Dyes from Indole Derivatives by Unspecific Peroxygenases and Their Application for In-Situ Dyeing

Tyrian purple (also known as royal or imperial purple) is the oldest known commercial pigment and still one of the most expensive dyes, often associated with the wardrobes of clergy and royalty. It is a brominated derivative of indigo, a natural dye that has been used since 4000 BC. Moreover, just recently, the therapeutic value of indigoids for the treatment of several disorders was discovered. The manufacturing of indigo derivatives by the existing chemical routes has become increasingly uninteresting due to the use of aggressive reagents, expensive starting materials and high-energy costs. Thus, both dyestuff manufacturers and the pharmaceutical industry are interested in the development of gentle preparation methods of indigoids from simple precursors. Here, we describe a simple enzymatic method for the one-step synthesis of Tyrian purple and other indigo derivatives with fungal peroxygenases (UPO, EC 1.11.2.1). The reaction does not require complex co-substrates and works well in phosphate buffers with H2O2 (<0.1 wt%) and less than 5% (v/v) acetonitrile as co-solvent. We demonstrate the scaling up of the reaction to 10 Liters and established thereupon an environmentally friendly combined synthesis and in-situ dyeing process, further simplifying the manufacturing of vat-dyed fabrics. Eventually, we screened a number of halogen-substituted indoles in the search for novel indigo derivatives, which may be of interest for pharmaceutical and/or dyeing purposes.

Synthesis and Characterization of Yellow Pigments (Li0.4RE0.6Al0.6)1/2MoO4–BiVO4 with High NIR Reflectance

In this work, a new type of near-infrared (NIR) reflective yellow pigment with a general formula of [(Li0.4RE0.6Al0.6)x/2Bi1–x][MoxV1–x]O4 was prepared by a solid-phase reaction calcined at a high temperature of 700 °C. X-ray diffraction (XRD), scanning electron microscope (SEM), a UV–vis–NIR spectrophotometer, and other methods were used to characterize the structure, morphology, and optical properties of synthetic pigments. For a series of [(Li0.4RE0.6Al0.6)x/2Bi1–x][MoxV1–x]O4 pigments, when x > 0.2, bismuth vanadate changes from the monoclinic phase (space group I2/b(15)) to the tetragonal scheelite phase (space group I41/a(88)). The structures of the pigments are all tetragonal scheelite phases, and the difference in their color rendering is mainly due to the differences between the valence band and the conduction band and the difference in the band gap caused by different rare earth elements. The NIR reflectance (R %) and NIR solar reflectance (R* %) of [(Li0.4La0.6Al0.6)0.1Bi0.8][Mo0.2V0.8]O4 pigments are 96.64 and 93.10% (b* = 77.13, C* = 77.6), respectively. In the acid and alkali resistance test, the color difference values ΔE* of the pigment before and after soaking are less than 5. Finally, the thermal infrared test of the synthetic pigments and commercial pigments on galvanized plates without or with TiO2 was performed. The experimental results show that the temperature difference between the synthetic pigment and commercial bismuth yellow can reach 11 °C. Therefore, it is believed that the synthetic pigment can reflect more heat radiation from sunlight and has better heat insulation performance. The synthetic pigment has higher reflectivity than the commercially available bismuth vanadate pigment, showing its application potential.

Environmentally benign rare earth pigments: effect of calcium dopant and tuning of bandgaps for different color hues

PurposeAs there is a strong inducement to develop new colored inorganic materials to substitute the current industrial pigments that are based on toxic metals hazardous to health and the environment, the purpose of this paper is to invent environmentally benign rare earth-based colorants as viable alternatives to the traditional toxic pigment formulations. Herein, the authors developed a series of rare earth pigments having the general formula Ca0.1 Ln0.9 PO4 ( Ln = Y , Pr , mixed rare earth oxides, RE and Di). After studying all the optical properties, the authors have gone for some coloring application in plastic like PMMA.Design/methodology/approachThe designed pigments were synthesized by traditional solid-state method. Stoichiometric amounts of each reagent were mixed in an agate mortar and the mixtures were calcined at optimized temperature 1000 °C for 4 h in electric furnace followed by auto–cooling. The samples were characterized by X-ray diffraction diffraction, UV–vis spectroscopy, scanning electron microscope (SEM), particle size distribution, color coordinates determination, acid/alkali test, thermo gravimetric (TG) analysis and CIE–1976 L*a*b* color scales. Among the various lanthanide ions and calcium ion as dopant, the pigment composition shows various hues ranges from green to yellow. The designed pigments consist of non–toxic elements and were further found to possess high thermal and chemical stability. The pigments were also found to be appropriate candidates for the coloration of polymer substrates like PMMA.FindingsThe present investigations establish that various color hues can be achieved by the incorporation of suitable chromophore metal ions like calcium in various rare earth host lattice by tuning of the band gaps. The coloring mechanism is based on the strong absorption of the pigments in the blue and red regions due to electronic transitions of the micro states of rare earth ion. The pigment composition shows various hues ranges from green to yellow. The coloring mechanism is based on the tuning of band gap by the dopant like calcium in various rare earth host lattice. In addition, this pigment was chemically and thermally stable. Finally, it has applied in plastics like PMMA.Research limitations/implicationsMechanism of the color appearance using band calculations and on possible applications of rare earth phosphate powders as pigments in plastics and paints have not been explored much. However, the properties of the Ca-doped rare earth phosphate implies that this material has a potential to be applied as a satisfactory pigment for coating or coloring except for glaze, which may cause a side reaction at high temperatures, especially taking into consideration the economics and ecologies. The possibility of Ca2+ incorporation in CePO4 with monazite structure-type has been established.Practical implicationsThe designed pigments consist of non-toxic elements and were further found to possess high thermal and chemical stability. The pigments were also found to be appropriate candidates for the coloration of polymer substrates. Thus, the present environmental friendly pigment powders may find potential alternative to the classical toxic inorganic pigments for various applications.Social implicationsThere is a strong incentive to design new colorants based on inorganic materials to substitute for industrial pigments that are based on heavy elements hazardous to health and the environment. However, several industrial yellow pigments such as cadmium yellow (CdS), chrome yellow (PbCrO4) and nickel titanium yellow (TiO2-NiO-Sb2O3) contain the harmful elements (e.g. Cd, Pb, Cr and Sb) for the human body as well as the environment. The designed pigments consist of non-toxic elements and were further found to possess high thermal and chemical stability. The pigments were also found to be appropriate candidates for the coloration of polymer substrates. Thus, the present environmental friendly pigment powders may find potential alternative to the classical toxic inorganic pigments for various applications.Originality/valueThere is a strong incentive to design new colorants based on inorganic materials to substitute for industrial pigments that are based on heavy elements hazardous to health and the environment. However, several industrial yellow pigments such as cadmium yellow (CdS), chrome yellow (PbCrO4) and nickel titanium yellow (TiO2-NiO-Sb2O3) contain the harmful elements (e.g. Cd, Pb, Cr and Sb) for the human body as well as the environment. So, the authors have developed new class of inorganic pigments that are both non-toxic and environmentally unimpeachable, while preserving or even exceeding the optical, thermal and chemical characteristics of the existing commercial pigments. The developed colorants find practical applications in polymer matrix like PMMA.

Antimicrobial activity of red pigments derived from Monascus purpureus: A comparison to industrial red pigments

AbstractBackgroundIn recent years, the various advantages of fungal pigments over other natural or synthetic pigments have opened new avenues for wide range of applications in different industries. This study aims to determine the antimicrobial activity of fungal pigment produced by Monascus purpureus CMU001, against some Gr(+) and Gr(−) bacteria, yeasts and molds.MethodIn this study, the 96‐well microplate dilution and macro dilution methods were used to determine the minimum inhibitory concentration (MIC) values of pigments on tested microorganisms. Therefore, the microbial plating method was performed to observe the antifungal activity of pigment since the MIC values could not be determined on molds.ResultsThe antibacterial activity of Monascus pigment against all tested bacteria was higher than the commercial red pigment. The minimum bactericidal concentration on Bacillus cereus ATCC11778 was determined as 256 mg/ml for the commercial pigment and 128 mg/ml for Monascus pigment. The MIC values could not be determined for both pigments against yeast and molds even at the highest possible concentration.ConclusionThe Monascus pigments have a big potential to use in different industries such as foods, textile, and biomedical products, since the high inhibitory effects was confirmed on various food‐borne and pathogenic bacteria and fungi. Although the specific mechanism and properties of the antimicrobial activity of Monascus pigments are still unknown, the differences between lab‐produced and commercial pigments showed that the antimicrobial activity was based on the type of microorganism, growth conditions, and the composition of culture medium.

Enhanced mobilization of Cd from commercial pigments in the rhizosphere of flooded lowland rice

Although yellow Cd pigments (Cd-YP), widely used in industrial colorants, are considered inert, increasing evidence suggests once released into the environment, photobleaching/weathering mobilizes Cd from these pigments posing a pollution threat. Although general redox conditions and biotic/microbial activity are known to be important factors in determining Cd release, how spatial trends and specific soil processes regulate the Cd-YP behavior are poorly understood. Using plant rhizotrons in controlled environmental conditions, this study investigated the behavior of Cd-YP amendments matched to levels (15 mg kg−1) representative of contaminated soils in Yixing, China. Using high-resolution two-dimensional diffusive-gradient-in-thin-films (HR-2D-DGT), planar-optode (PO) multilayer systems alongside targeted soil and porewater sampling for chemical analysis the biogeochemistry associated with Cd mobilization from Cd-YP rice rhizospheres were determined. The results showed that there was a significant release of Cd into soil porewaters (51.5 μg L−1), but this reduced by 90.9% and stabilized over time (after 6-days). HR-2D-DGT ion-maps revealed pronounced spatial variances. The flux-maxima for Cd, which located within aerobic-rhizosphere zones, was 9 to 19-fold higher than in associated anoxic bulk soil. In general, zones of radial O2 loss (ROL)/higher redox conditions and lower pH were associated with Cd release, with S2− to SO42− transitions marking the boundaries of high-flux areas. Some isolated colocalization of Fe and Cd hotspots were observed in lateral root regions, but on-the-whole Fe/Mn and Cd release were not linked. In addition, microniche development was also an important feature of Cd mobilization due to soil heterogeneity.

A Convenient Synthesis of Diketopyrrolopyrrole Dyes.

Diketopyrrolo[3,4-c]pyrroles (DPP) are high-performance organic optoelectronic materials. They have applications in solar cells, fluorescent probes, bioimaging, photodynamic/photothermal therapy, and in many other areas. This article reports a convenient two-step synthesis of various DPP dyes from Pigment Red 254, an inexpensive commercial pigment. The synthesis includes a Suzuki–Miyaura cross-coupling reaction of a bis(4-chlorophenyl)DPP derivative with aryl and hetaryl boronic acids under mild reaction conditions. The new dyes show large Stokes shifts and high fluorescence quantum yields, important features for their potential use in technical and biological applications.

Perylene and perinone pigments

Abstract Perylenes and perinones are separate groups of pigments categorized within the carbonyl chemical class. The two pigment groups show similarities, for example, in their chemical structural features and, to an extent, in their technical and application properties as high-performance organic pigments. Perylenes constitute a series of firmly established high-performance pigments, offering red and violet colors, and also extending to black. Synthetically, they are derived from perylene-1,4,5,8-tetracarboxylic acid. The perylenes tend to be quite expensive pigments, but their high levels of fastness properties mean that they are suitable for highly demanding applications. In particular, they offer very high heat stability. Two perinone pigments are used commercially. In their synthesis from naphthalene-1,4,5,8-tetracarboxylic acid, they are formed as mixtures of the two isomers, which can be separated. The trans isomer, CI Pigment Orange 43, is a highly important commercial pigment, especially for plastics, while the cis isomer, CI Pigment Red 194, is bordeaux in color and is of much lesser importance. The perinone, CI Pigment Orange 43, provides a brilliant orange color and has very good fastness properties. Its commercial manufacture involves a challenging multistage procedure and consequently it is one of the most expensive organic pigments on the market.