Synthesis of β-Ca2P2O7 as an Adsorbent for the Removal of Heavy Metals from Water

In the present work, beta-calcium pyrophosphate (β-Ca2P2O7) was investigated as a potential adsorbent for the removal of heavy metal ions from water. Single-phase β-Ca2P2O7 powders were synthesized by a simple, scalable and cost-effective wet precipitation method followed by annealing at 800 °C, which was employed for the conversion of as-precipitated brushite (CaHPO4∙2H2O) to β-Ca2P2O7. Physicochemical properties of the sorbent were characterized by means of X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), thermal analysis (TGA/DSC), scanning electron microscopy (SEM) and low temperature adsorption–desorption of nitrogen (BET method). The synthesized powders consisted of porous plate-like particles with micrometer dimensions. Specific surface area calculated by the BET method was found to be 7 m2 g−1. For the estimation of sorption properties, the aqueous model solutions containing different metal ions (Al3+, Cd2+, Co2+, Cu2+, Fe2+, Mn2+, Ni2+, Pb2+, Sn2+, Sr2+ and Zn2+) were used. The adsorption test revealed that β-Ca2P2O7 demonstrates the highest adsorption capacity for Pb2+ and Sn2+ ions, while the lowest capacity was observed towards Sr2+, Ni2+ and Co2+ ions. The optimal pH value for the removal of Pb2+ ions was determined to be 2, which is also related to the low solubility of β-Ca2P2O7 at this pH. The adsorption capacity towards Pb2+ ions was calculated as high as 120 mg g−1

Synthesis and Characterization of Graphite Intercalation Compounds with Sulfuric Acid

In this work, graphite intercalation compounds (GICs) were synthesized using three different oxidizers: (NH4)2S2O8, K2S2O8, and CrO3 with and without P2O5 as a water-binding agent. Furthermore, the samples obtained were heat-treated at 800 °C. Specimens were characterized by optical microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). The correlation between different characteristic parameters of the Raman analysis has shown that the use of CrO3 results in a much higher structural disorder compared to the products obtained using persulfate oxidizers. Narrowing the correlation set revealed that minimal defect concentration can be reached by using K2S2O8, while the use of (NH4)2S2O8 causes a slightly higher concentration of defects. It was also established that the additional use of P2O5 can help to achieve more effective intercalation and has a positive effect on the formation of the stage I GIC phase. After heat treatment, the intercalated products mostly return to a graphite-like structure; however, the samples obtained with CrO3 stand out with the most significant changes in their surface morphology. Therefore, analysis suggests that GICs obtained using persulfate oxidizers and P2O5 could be a candidate to produce high-quality graphene or graphene oxide

L-Glutamate Biosensor for In Vitro Investigations: Application in Brain Extracts

Investigations of L-glutamate release in living organisms can help to identify novel L-glutamate-related pathophysiological pathways, since abnormal transmission of L-glutamate can cause many neurological diseases. For the first time, a nitrogen-modified graphene oxide (GO) sample (RGO) is prepared through a simple and facile one-pot hydrothermal reduction of GO in the presence of 20 wt.% of the dye malachite green and is used for amperometric biosensing. The biosensor demonstrates adequate stability and is easy to prepare and calibrate. The biosensor detects the current generated during the electrooxidation of hydrogen peroxide released in the L-glutamate that is converted to the alpha-ketoglutarate catalyzed by L-glutamate oxidase. The biosensor consists of a semipermeable membrane, with L-glutamate oxidase (EC 1.4.3.11) immobilized in albumin and RGO and the working Pt electrode. First, the basic version of the L-glutamate biosensor is examined in PBS to investigate its sensitivity, reliability, and stability. To demonstrate the applicability of the L-glutamate biosensor in the analysis of complex real samples, quantification of L-glutamate in bovine brain extract is performed and the accuracy of the biosensor is confirmed by alternative methods. The enhanced version of the L-glutamate biosensor is applied for L-glutamate release investigations in a newly developed strain of rats (DAT-knockout, DAT-KO)