Search Results (22)

This study investigates the adsorption and desorption efficiencies of Cu (II) and Cd (II) from industrial effluents using orange peel powder and a newly developed mixed adsorbent composed of equal parts of activated charcoal (AC) and bone charcoal (BC). The mixed adsorbent (AC + BC) exhibited significantly higher removal efficiencies for both copper and cadmium metal ions compared to orange peel powder. This can be attributed to the high surface area of AC and the negative surface charge of BC, resulting in a synergistic adsorption effect. Batch adsorption experiments were conducted in an orbital shaker at 150–180 rpm for 60 min, followed by thorough rinsing to remove any residual metal ions. The optimal pH for maximum adsorption of Cu (II) and Cd (II) was found to be 6. The effects of adsorbent dosage (ranging from 0.5 to 5 g/L) and contact time (ranging from 15 min to 4 h) on adsorption performance were systematically studied. Regeneration experiments using 0.2 M HCl demonstrated that the adsorption of Cu (II) and Cd (II) on the mixed adsorbent was highly reversible, achieving desorption efficiencies of 90% and 94%, respectively. Notably, Cd (II) consistently exhibited higher desorption rates across all tested dosages. These results confirm the potential of the proposed adsorbent and regeneration strategy for efficient and economical removal of heavy metals from industrial wastewater. Full article

At present, the amount of heavy metals in some aquifers exceeds the limits established by standards, especially in developing countries. Cadmium is present in high concentrations in aquifers; contact with cadmium can lead to some adverse health effects. Adsorption is one of the most efficient and low-cost methods currently used to separate heavy metals from water systems. In order to obtain a sustainable heavy metal adsorption system, abundant, low-cost, biodegradable, and easy-to-treat organic waste compounds were sought. Three biosorbents were chosen: orange, peanut, and banana peel, which, due to their functional groups, can attract the positive ions of metals and form a bond that allows them to be absorbed and separated from the aqueous solution. The presence of functional groups such as -OH, -CO, -COO⁻, and -N-H were found to be the main responsible for biosorption (FTIR). Square wave voltammetry was used to analyze the amount of cadmium in an aqueous solution. It was found that the systems with the best adsorption capacities were untreated peanut peel (284.2 mg/g), untreated orange peel (275.5 mg/g), and treated banana peel (229.21 mg/g). Treatment of the peels for cadmium uptake is not recommended. Full article

Photocatalysis, mainly using TiO₂ as a catalyst, has emerged as a promising method to address the issue of wastewater treatment. This study explores the enhanced photocatalytic activity of TiO₂ through the introduction of reduced graphene oxide (rGO) and cadmium sulfide (CdS) as selective metal dopants. The incorporation of rGO and CdS into the TiO₂ lattice aims to optimize its photocatalytic properties, including bandgap engineering, charge carrier separation, and surface reactivity. The unique combination of CdS and rGO with TiO₂ is expected to boost degradation efficiency and reduce the reliance on expensive and potentially harmful sensitizers. This experimental investigation involves the synthesis and characterization of TiO₂-based photocatalysts. The photocatalytic degradation of methyl orange (MO) and methylene blue (MB) was assessed under controlled laboratory conditions, studying the influence of metal dopants on degradation kinetics and degradation efficiency. Furthermore, the synthesized photocatalyst is characterized by advanced techniques, including BET, SEM, TEM, XRD, and XPS analyses. The degraded samples were analyzed by UV-Vis spectroscopy. Insights into the photoexcitation and charge transfer processes shed light on the role of metal dopants in enhancing photocatalytic performance. The results demonstrate the potential of a TiO₂-rGO-CdS-based photocatalyst in which 100% degradation was achieved within four hours for MO and six hours for MB, confirming efficient azo dye degradation. The findings contribute to understanding the fundamental principles underlying the photocatalytic process and provide valuable guidance for designing and optimizing advanced photocatalytic systems. Ultimately, this research contributes to the development of sustainable and effective technologies for removing azo dyes from various wastewaters, promoting environmental preservation and human well-being. Full article

Orange peel biochar (C)-supported cadmium sulfide composites (CdS-C) were prepared by the combination of hydrothermal and calcination methods. The structure and morphology were characterized in detail by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The CdS-C composite with 60% CdS exhibited the highest photocatalytic hydrogen production rate of 7.8 mmol·g⁻¹·h⁻¹, approximately 3.69 times higher than that of synthesized CdS without biochar. These results indicate that biochar derived from orange peel could be a low-cost, renewable, environmentally friendly, and metal-free co-catalyst for CdS, enhancing its photostability. Full article

In this report, we present the results on the physicochemical characterization of cadmium telluride quantum dots (QDs) stabilized with glutathione and prepared by optimizing the synthesis conditions. An excellent control of emissions and the composition of the nanocrystal surface for its potential application in monoclonal antibody and biomarker testing was achieved. Two samples (QDYellow, QDOrange, corresponding to their emission colors) were analyzed by dynamic light scattering (DLS), and their hydrodynamic sizes were 6.7 nm and 19.4 nm, respectively. Optical characterization by UV-vis absorbance spectroscopy showed excitonic peaks at 517 nm and 554 nm. Photoluminescence spectroscopy indicated that the samples have a maximum intensity emission at 570 and 606 nm, respectively, within the visible range from yellow to orange. Infrared spectroscopy showed vibrational modes corresponding to the functional groups OH-C-H, C-N, C=C, C-O, C-OH, and COOH, which allows for the formation of functionalized QDs for the manufacture of biomarkers. In addition, the hydrodynamic radius, zeta potential, and approximate molecular weight were determined by dynamic light scattering (DLS), electrophoretic light scattering (ELS), and static light scattering (SLS) techniques. Size dispersion and the structure of nanoparticles was obtained by Transmission Electron Microscopy (TEM) and by X-ray diffraction. In the same way, we calculated the concentration of Cd²⁺ ions expressed in mg/L by using the Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-OES). In addition to the characterization of the nanoparticles, the labeling of murine myeloid cells was carried out with both samples of quantum dots, where it was demonstrated that quantum dots can diffuse into these cells and connect mostly with the cell nucleus. Full article

Batch experiments were conducted to test orange waste (OW), an agricultural solid waste byproduct from the orange juice manufacturing industry, as adsorbent for binary solutions of Cd²⁺-Cr³⁺ and Zn²⁺-Cr³⁺. Fourier transform infrared spectroscopy (FTIR) and the point of zero charge (pH_pzc) were used to identify the functional groups on the OW surface involved in biosorption. The biosorption equilibrium data for both binary-metal solutions were obtained and fitted to various isotherm models. The extended Sips and the non-modified Redlich-Peterson isotherm models gave the best fit for the experimental data. According to the extended Sips model, the maximum biosorption capacity of OW was 0.573 mmol·g⁻¹ for Cd²⁺, 0.453 mmol·g⁻¹ for Zn²⁺, and 1.96 mmol·g⁻¹ for Cr³⁺. The sorption capacity dropped to 0.061 mmol·g⁻¹ for Cd²⁺ and to 0.101 mmol·g¹ for Zn²⁺ in their binary systems with Cr³⁺ for the higher initial metal concentrations in the solution. However, the maximum sorption capacity of chromium was only slightly affected by the presence of Cd²⁺ or Zn²⁺. For both binary systems, the presence of a second metal ion in the solution always conduces to a reduction in the sorption of the other metal in the solution. The presence of Cr³⁺ decreased the sorption of Cd²⁺ and Zn²⁺ more than vice versa. Conclusively, effective removal of Cr³⁺ ions from an aqueous solution can still be achieved in the presence of Cd²⁺ or Zn²⁺. Full article

Amendments with activators or microorganisms to enhance phytoremediation in toxic-metal-polluted soils have been widely studied. In this research, the production of indoleacetic acid, siderophore, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase by phosphate-solubilizing bacteria was investigated during a pure culture experiment. Pot experiments were performed using Cd-polluted soil with the following treatments: control (CK, only ultrapure water), orange-peel-based activator (OG), and a combination of phosphate-solubilizing bacteria (Acinetobacter pitti) and OG (APOG). Ryegrass plant height and fresh weight, Cd content in ryegrass, total and available Cd soil content, soil enzyme activity, and soil bacterial diversity were determined in this work. The findings showed that the height of ryegrass in OG and APOG increased by 14.78% and 21.23%. In the APOG group, a decreased ratio of Cd was 3.37 times that of CK, and the bioconcentration factor was 1.28 times that of CK. The neutral phosphatase activity of APOG was 1.33 times that of CK and catalase activity was 1.95 times that of CK. The activity of urease was increased by 35.48%. APOG increased the abundance of beneficial bacteria and Proteobacteria was the dominant bacterium, accounting for 57.38% in APOG. Redundancy analysis (RDA) showed that nutrient elements were conducive to the propagation of the dominant bacteria, the secretion of enzymes, and the extraction rate of Cd in the soil. The possible enhancement mechanism of phytoremediation of cadmium by A. pitti combined with OG was that, on the one hand, APOG increased soil nutrient elements and enzyme activities promoted the growth of ryegrass. On the other hand, APOG activated Cd and boosted the movement of Cd from soil to ryegrass. This research offers insight for the combination of phosphate-solubilizing bacteria with an orange-peel-based activator to improve phytoremediation of Cd-contaminated soils and also provides a new way for the resource utilization of fruit residue. Full article

Of the different renewable sources of energy, photovoltaic energy has one of the highest potentials. In recent decades, several technological and research advances have contributed to the consolidation of its potential. One current photovoltaic energy research topic is the analysis of the impact of sediments on the panels’ performance. The development of models to predict the performance of panels in the presence of sediments may allow for better decision-making when considering maintenance operations. This work contributed to the investigation of the influence of sand on the production of photovoltaic energy in cadmium telluride (CdTe) panels. Six panels of this type with different colors and transparencies were experimentally tested with and without the presence of sand. The impact of the sand on the cells’ performance was evaluated by analyzing the change in the 1M5P model’s parameters and in the power, efficiency, and fill factors. The experimental results show different negative impacts on the output power of the CdTe panels, from −14% in the orange panel to −36% in the green panel. Based on this study, the development of a model capable of predicting the effect of the sand on these panels was introduced. The developed model was validated experimentally, with a maximum deviation of 4.6%. These results can provide support for the decision-making around maintenance activities and for the development of new techniques to avoid sediment deposition on CdTe panels. Full article

Thiosulfate is an inorganic ligand that forms a soluble light-sensitive cadmium thiosulfate complex, and cadmium sulfide (CdS) with a “size effect” can be produced via ultraviolet (UV) irradiation. This study investigated the activity of CdS nanoparticles (NPs) precipitated from a cadmium thiosulfate complex via UV irradiation on photocatalytic dye degeneration. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrated that the decomposition products were spherical CdS NPs. The photocatalytic activity of the CdS NPs was evaluated based on the degradation rates of methylene blue, rhodamine B, and methyl orange. With 25 mg of CdS NPs and a dye concentration of 10 mg L⁻¹, the degradation rates of the three dyes under visible light were 36%, 90%, and 80%, respectively. A kinetic study revealed that the photocatalytic degradation rate of the CdS NPs followed first-order kinetics, and the rate constants for the three dyes were determined to be 0.0051, 0.0762, and 0.0144 min⁻¹, respectively. The CdS NPs exhibited a stable photocatalytic performance after three cycles of methylene blue degradation. This indicates that CdS NPs formed from a cadmium thiosulfate complex after UV irradiation can be used for photocatalysis, which will save resources and help in environmental conservation. Full article

Heavy metals in the environment cause adverse effects on living organisms. Agro-wastes have the potential to remove heavy metals from aqueous solutions. In this study, the orange peel cellulose (OPC) beads were utilized as adsorbents to remove metals from wastewater. The surface of the adsorbent was studied by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy coupled with energy dispersive x-ray spectroscopy (SEM-EDS). The concentrations of the metals before and after adsorption were measured using inductively coupled plasma mass spectrometry. The removal of the metal ions (i.e., Cr⁶⁺, Cd²⁺, and Pb²⁺) using the OPC was investigated by varying the pH, contact time, and adsorbent dosages parameters. The maximum removal efficiency obtained for the metal ions occurred at pHs 4–8. The use of the Langmuir isotherm and Freundlich isotherm models demonstrated the statistical significance of the heavy metal adsorption processes (R² > 0.96). At a neutral pH, the OPC adsorption order was Pb²⁺ > Cd²⁺ > Cr⁶⁺ with % removal values of 98.33, 93.91, and 33.50, respectively. The adsorption equilibrium for Cr⁶⁺ was reached after 36 h. For Cd²⁺ and Pb²⁺, equilibrium was reached after 8 and 12 h, respectively. The FT-IR and SEM-EDS confirmed the presence of many functional groups and elements on the adsorbent. The adsorption of heavy metals using the OPC is a low-cost, eco-friendly, and innovative method for the removal of metals in aquatic environments. The findings of this study will be highly significant for the public in the affected areas worldwide that have credible health concerns due to water contamination with heavy metals. Full article

Cadmium yellow degradation afflicts numerous paintings realized between the XIXth and XXth centuries. The degradation process and its kinetics is not completely understood. It consists of chalking, lightening, flaking, spalling, and, in its most deteriorated cases, the formation of a crust over the original yellow paint. In order to improve the comprehension of the process, mock-up samples of CdS in yellow and orange tonalities were studied by means of structural analysis and optical characterization, with the principal techniques used in the field of cultural heritage. Mock ups were artificially degraded with heat treatment and UV exposure. Relevant colorimetric variation appears in CIE Lab coordinates from reflectance spectra. XRD, SEM-EDS, and Raman spectroscopy revealed the formation of cadmium sulfate, whilst time-resolved photoluminescence and pump–probe transient absorption spectroscopy suggest the formation of a defective phase, compatible with Cd vacancies and the formation of both CdO and CdSO₄ superficial clusters. Full article

Heavy metal contamination has spread around the world, particularly in emerging countries. This study aimed to assess the effectiveness of starch/eggshell/orange peel-activated carbon-based composite films in removing cadmium (II) ions from water samples. X-ray diffraction and scanning electron microscopy were used to characterize the composite films. The effect of Cd²⁺ was studied using a UV-Vis spectrophotometer and atomic absorption spectroscopy. The morphology of the composite film reveals a highly porous and rough surface with more open channels and a non-uniform honeycomb, indicating that the film has a high potential to adsorb Cd²⁺. The diffraction peaks for this film were found to be at 13.74°, 17.45°, 18.4°, and 23.6°, indicating a typical crystalline A-type packing arrangement within the starch granules. The results indicate that crystalline structure was unaffected by the addition of eggshell powder and orange peel-activated carbon. In 0.5 mg L⁻¹ and 1.0 mg L⁻¹ Cd²⁺ ions, the composite film removed 100% and 99.7% of the Cd²⁺, respectively, while the maximum removal efficiency for methylene blue was 93.75%. Thus, the current study shows that starch/eggshell/orange peel activated carbon film has a high potential for commercial activated carbon as a low-cost adsorbent. Full article

Pollution by dyes and heavy metals is one of the main concerns at the environmental level due to their toxicity and inefficient elimination by traditional water treatment. Orange peel (OP) without any treatment was applied to effectively eliminate methylene blue (MB) and cadmium ions (Cd²⁺) in mono- and multicomponent systems. Although the single adsorption processes for MB and Cd²⁺ have been investigated, the effects and mechanisms of interactions among multicomponent systems are still unclear. Batch experiments showed that in monocomponent systems, the maximum adsorption capacities were 0.7824 mmol g⁻¹ for MB and 0.2884 mmol g⁻¹ for Cd²⁺, while in multicomponent systems (Cd²⁺ and MB), both contaminants competed for the adsorption sites on OP. Particularly, a synergic effect was observed since the adsorption capacity of Cd²⁺ increased compared to the monocomponent system. Results of desorption and adsorbent reuse confirmed that the adsorbent presents good regeneration performance. The low cost of this material and its capacity for the individual or simultaneous removal of Cd²⁺ and MB in aqueous solutions makes it a potential adsorbent for polluted water treatment processes. Full article

The comprehensive technical investigation of female nude paintings by the Singapore pioneer artist Liu Kang (1911–2004) provided the evidence for a discussion of the evolution of his palette of colours and his working process for expression in this genre, particularly the execution of female bodies. As the artist’s free expression in classical nude paintings was limited by the censorship imposed by the Singapore government, the investigated artworks span two periods, 1927–1954 (early career) and 1992–1999 (the “golden years”, during which censorship policies were relaxed). Hence, eight paintings from the Liu family and National Gallery Singapore were selected for non- and micro-invasive analyses of the paint layers. The obtained results were supplemented with archival sources to elucidate certain aspects of Liu Kang’s working practice. The investigation revealed the importance of drawing and sketching studies in the development of artistic ideas. The analytical techniques, such as polarised light microscopy (PLM), field emission scanning electron microscope with energy dispersive spectroscopy (FE-SEM-EDS) and attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR), enabled us to observe a transition from the yellow iron-based tonal ranges of skin colours to complex pigment mixtures composed of additions of cobalt blue, ultramarine, Prussian blue, Cr-containing yellow(s) and green(s), cadmium yellow, orange and/or red and organic reds, revealing the artist’s more liberal use of colours and his experimentation with their contrasting and complementary juxtaposes. In terms of painting technique, the artist’s comparatively laborious paint application using small brushes quickly gave way to a more effortless manipulation of the paint using bigger brushes and the incorporation of palette knives. Moreover, visible light (VIS), near-infrared (NIR) and X-ray radiography (XRR) imaging techniques led to the discovery of a hidden composition in one investigated artwork, which bears resemblance to the nude painting known only from an archival photograph. Additionally, for the first time, the archival search provided photographic evidence that Liu Kang used oil paint tubes from Royal Talens and Rowney in the 1990s. Overall, this in-depth investigation contributes to the understanding of Liu Kang’s approach to the female nude painting and may assist conservators and art historians in studies of twentieth-century commercial paints. Full article

CdS nanoparticles were successfully synthesized using cadmium acetate and sodium sulfide as Cd and S precursors, respectively. The effect of using sodium thiosulfate as an additional sulfur precursor was also investigated (combined milling). The samples were characterized by XRD, Raman spectroscopy, XPS, UV-Vis spectroscopy, PL spectroscopy, DLS, and TEM. Photocatalytic activities of both CdS samples were compared. The photocatalytic activity of CdS, which is produced by combined milling, was superior to that of CdS, and was obtained by an acetate route in the degradation of Orange II under visible light irradiation. Better results for CdS prepared using a combined approach were also evidenced in photocatalytic experiments on hydrogen generation. The antibacterial potential of mechanochemically prepared CdS nanocrystals was also tested on reference strains of E. coli and S. aureus. Susceptibility tests included a 24-h toxicity test, a disk diffusion assay, and respiration monitoring. Bacterial growth was not completely inhibited by the presence of neither nanomaterial in the growth environment. However, the experiments have confirmed that the nanoparticles have some capability to inhibit bacterial growth during the logarithmic growth phase, with a more substantial effect coming from CdS nanoparticles prepared in the absence of sodium thiosulfate. The present research demonstrated the solvent-free, facile, and sustainable character of mechanochemical synthesis to produce semiconductor nanocrystals with multidisciplinary application. Full article