Graphene Prepared via the Dry Ice in Flames Method and its Purification Using Different Routes: A Comparative Study

Although the dry ice method used to synthesize exfoliated graphite/graphene is little known and used, it has significant advantages over others: it is low cost, simple, and a large quantity of material can be obtained using some inorganic and highly available acids (which can be reused). Despite the above advantages, the main reason for its incipient development is the resulting presence of magnesium oxide in the final product. In the present work, three different treat-ments were tested to remove this remnant using some acid chemical leaching processes, making use of hydrochloric acid, aqua regia, and piranha solution. Based on the experimental evidence, it was found that using aqua regia and combining the leaching process with mechanical milling was the most efficient way of removing such a remnant, the residue being only 0.9 wt.%. This value is low when compared to that obtained with the other acid leaching solutions and purifi-cation process (2.8 - 29.6 wt.%). A mandatory high-energy mechanical milling stage was neces-sary during this treatment, in order to expose and dissolve the highly insoluble oxide without secondary chemical reactions on the graphenes. High-energy mechanical milling is an effective route to exfoliate graphite/graphene, which allows the magnesium oxide to be more susceptible to acid treatment. The obtained surface area was 504 m2g-1; this high value resulting from the in-tense exfoliation can potentiate the use of this material for a wide variety of applications.

Synthesis, In Vitro Testing, and Biodistribution of Surfactant-Free Radioactive Nanoparticles for Cancer Treatment

New forms of cancer treatment, which are effective, have simple manufacturing processes, and easily transportable, are of the utmost necessity. In this work, a methodology for the synthesis of radioactive Gold-198 nanoparticles without the use of surfactants was described. The nuclear activated Gold-198 foils were transformed into H198AuCl4 by dissolution using aqua regia, following a set of steps in a specially designed leak-tight setup. Gold-198 nanoparticles were synthesized using a citrate reduction stabilized with PEG. In addition, TEM results for the non-radioactive product presented an average size of 11.0 nm. The DLS and results for the radioactive 198AuNPs presented an average size of 8.7 nm. Moreover, the DLS results for the PEG-198AuNPs presented a 32.6 nm average size. Cell line tests showed no cytotoxic effect in any period and the concentrations were evaluated. Furthermore, in vivo testing showed a high biological uptake in the tumor and a cancer growth arrest.

Heavy metals in private car dusts collected from Universiti Malaysia Pahang, Gambang Campus: Contamination and human health risks

A pilot study was conducted to investigate the concentrations of seven heavy metals (Zn, Cu, Cr, Cd, Fe, Ni and Pb) in private car dusts collected from Universiti Malaysia Pahang (UMP), Gambang campus. Ten private cars were selected among UMP staffs and students, and the dust samples were obtained by using a conventional vacuum cleaner with a clean nylon sampling sock pre-inserted into the suction nozzle. All samples were acid-digested with aqua regia solution and analysed for metal concentration using Atomic Absorption Spectrometry (AAS). The highest mean concentrations were recorded for Fe (650± 480 mg/kg), followed by Zn (160 ± 110 mg/kg), Cu (76.2 ± 18.5 mg/kg), Pb (39.2 ± 99.1 mg/kg), Ni (6.39 ± 8.30 mg/kg), Cr (3.42 ± 5.90 mg/kg) and Cd (0.55 ± 1.40 mg/kg). Hazard quotient (HQ) and hazard index (HI) values lower than 1 indicated no potential non-carcinogenic risks to the adult drivers.

Kajian pengaruh kondisi dekomposisi analisis logam tembaga dalam sedimen di pelabuhan ikan Sendang Biru secara SSA

Cu that is absorbed in marine sediments can accumulate in the food chain even in small concentrations. Cu analysis in these sediments can be used to analyze water pollution due to human activities. The purpose of this study was to determine the level of Cu in decomposed sediments with variation of solvent concentration, variation of decomposition time, and variation of solvent volume and then compare the result of Cu analysis decomposed using HNO3 solvent under effective condition with aqua regia solvent. The method of analysis used is decomposition technique of sediment sample by using reflux and then analyzed with AAS.. Cu yang terserap dalam sedimen laut dapat berakumulasi dalam rantai makanan meskipun dalam konsentrasi kecil. Analisis Cu dalam sedimen ini dapat digunakan untuk menganalisis pencemaran perairan akibat aktivitas manusia. Tujuan penelitian ini adalah menentukan kadar Cu dalam sedimen yang didekomposisi dengan variasi konsentrasi pelarut, variasi waktu dekomposisi, dan variasi volume pelarut dan membandingkan hasil analisis Cu yang didekomposisi menggunakan pelarut HNO3 pada kondisi efektif dengan pelarut akuaregia. Metode analisis yang digunakan yaitu teknik dekomposisi sampel sedimen dengan menggunakan refluks dan dianalisis dengan SSA.

Recovery of Platinum Group Metals from Spent Automotive Catalysts Using Lithium Salts and Hydrochloric Acid

The recovery of platinum group metals (PGMs) from waste materials involves dissolving the waste in an aqueous solution. However, since PGMs are precious metals, their dissolution requires strong oxidizing agents such as chlorine gas and aqua regia. In this study, we aimed to recover PGMs via the calcination of spent automotive catalysts (autocatalysts) with Li salts based on the concept of “spent autocatalyst + waste lithium-ion batteries” and leaching with only HCl. The results suggest that, when Li2CO3 was used, the Pt content was fully leached, while 94.9% and 97.5% of Rh and Pd, respectively, were leached using HCl addition. Even when LiF, which is a decomposition product of the electrolytic solution (LiPF6), was used as the Li salt model, the PGM leaching rate did not significantly change. In addition, we studied the immobilization of fluorine on cordierite (2MgO·2Al2O3·5SiO2), which is a matrix component of autocatalysts. Through the calcination of LiF in the presence of cordierite, we found that cordierite thermally decomposed, and fluorine was immobilized as MgF2.

Suitability of surficial media for Ni-Cu-PGE exploration in an established mining camp: a case study from the South Range of the Sudbury Igneous Complex, Canada

A geochemical study over the southwestern part of the South Range of the Sudbury Igneous Complex (SIC) was completed to assess the suitability of surficial media (humus, B-horizon soil and C-horizon soil) for delineating geochemical anomalies associated with Ni-Cu-PGE mineralization. Another objective was to test whether Na pyrophosphate can eliminate the effects of anthropogenic contamination in humus. Results of this study suggest that the natural geochemical signature of humus is strongly overprinted by anthropogenic contamination. Despite no indication of underlying or nearby mineralization, metal concentrations in humus samples by aqua regia collected downwind from smelting operations are higher compared to background, including up to 13 times higher for Pt, 12 times higher for Cu and 9 times higher for Ni. The high anthropogenic background masks the geogenic signal such that it is only apparent in humus samples collected in the vicinity of known Ni-Cu-PGE deposits. Results of this study also demonstrate that anthropogenically-derived atmospheric fallout also influences the upper B-horizon soil; however, lower B-horizon soil (at > 20 cm depth) and C-horizon soil (both developed in till) are not affected. Glacial dispersal from Ni-Cu-PGE mineralization is apparent in C-horizon till samples analyzed in this study. Compared to the background concentrations, the unaffected C-horizon till samples collected immediately down-ice of the low-sulfide, high precious metal (LSHPM) Vermilion Cu-Ni-PGE deposit are enriched over 20 times in Pt (203 ppb), Au (81 ppm) and Cu (963 ppm), and over 30 times in Ni (1283 ppm).Supplementary material:https://doi.org/10.6084/m9.figshare.c.5691080

Tuneable separation of gold by selective precipitation using a simple and recyclable diamide

The efficient separation of metals from ores and secondary sources such as electronic waste is necessary to realising circularity in metal supply. Precipitation processes are increasingly popular and are reliant on designing and understanding chemical recognition to achieve selectivity. Here we show that a simple tertiary diamide precipitates gold selectively from aqueous acidic solutions, including from aqua regia solutions of electronic waste. The X-ray crystal structure of the precipitate displays an infinite chain of diamide cations interleaved with tetrachloridoaurate. Gold is released from the precipitate on contact with water, enabling ligand recycling. The diamide is highly selective, with its addition to 29 metals in 2 M HCl resulting in 70% gold uptake and minimal removal of other metals. At 6 M HCl, complete collection of gold, iron, tin, and platinum occurs, demonstrating that adaptable selective metal precipitation is controlled by just one variable. This discovery could be exploited in metal refining and recycling processes due to its tuneable selectivity under different leaching conditions, the avoidance of organic solvents inherent to biphasic extraction, and the straightforward recycling of the precipitant.

Graphene Prepared via the Dry Ice in Flames Method and Its Purification Using Different Routes: A Comparative Study

Although the dry ice method used to synthesize exfoliated graphite/graphene is little known and used, it has significant advantages over others: it is low cost, simple, and a large quantity of material can be obtained using some inorganic and highly available acids (which can be reused). Despite the above advantages, the main reason for its incipient development is the resulting presence of magnesium oxide in the final product. In the present work, three different treatments were tested to remove this remnant using some acid chemical leaching processes. Based on the experimental evidence, it was found that using aqua regia, among other chemical mixtures, was the most efficient way of removing such as remnant, the residue being only 0.9 wt.%. A mandatory high-energy mechanical milling stage was necessary during this treatment, in order to expose and dissolve the highly insoluble oxide without secondary chemical reactions on the graphenes. The obtained surface area was 504 m2g-1; this high value resulted from the intense exfoliation can potentiate the use of this material for a wide variety of applications.

Development and Validation of an Analytical Method for Determination of Al, Ca, Cd, Fe, Mg and P in Calcium-Rich Materials by ICP OES

Four procedures based on closed-vessel microwave-assisted wet digestion with different oxidative reagents, including HNO3 (P1), HNO3 + H2O2 (P2), aqua regia (P3) and Lefort aqua regia (P4), for preparation of calcium (Ca)-rich materials prior to determination of total concentrations of Al, Ca, Cd, Fe, Mg and P by inductively coupled optical emission spectrometry (ICP OES) were compared. It was found that digestion with Lefort aqua regia (P4) provided the best results for all examined elements, i.e., precision of 0.30–4.4%, trueness better than 2%, recoveries of added elements between 99.5–101.9%, and limits of detection within 0.08–1.8 ng g−1. Reliability of this procedure was verified by analysis of relevant certified reference materials (CRMs), i.e., Natural Moroccan Phosphate Rock—Phosphorite (BCR-O32). Additionally, selection of appropriate analytical lines for measurements of element concentrations, linear dynamic ranges of calibration curves and matrix effects on the analyte response were extensively investigated. Finally, the selected procedure was successfully applied for routine analysis of other Ca-rich materials, i.e., CRMs such as NIST 1400 (Bone Ash), CTA-AC-1 (Apatite Concentrate Kola Peninsula) and NCS DC70308 (Carbonate Rock), and six natural samples, such as a dolomite, a phosphate rock, an enriched superphosphate fertilizer, pork bones, pork bones after incineration, and after steam gasification.