ABSTRACT
This work presents efficient tetracycline (TC) antibiotics adsorption using a functional porous phosphate/carbonate composite (PCC). The PCC was fabricated by anion-exchange of phosphate on the surface of vaterite-phase calcium carbonate particle scaffolds. The PCC, having dense nanoporous network coverage with large surface area and pore volume, exhibited excellent TC adsorption in solution. Its adsorption isotherm fitted well to the Freundlich model, with a maximum adsorption capacity of 118.72 mg/g. The adsorption process was spontaneous, endothermic, and followed pseudo-second-order kinetics. From the XPS analysis, the hydrogen bonding and surface complexation were the key interactions in the process. In addition, a colorimetric TC detection method was developed considering its complexation with phosphate ions, originating from PCC dissolution, during adsorption. The method was used to detect TC in mg/L concentrations in water samples. Thus, the multifunctional PCC exhibited potential for use in TC removal and environmental remediation.
Subject(s)
Heterocyclic Compounds , Nanopores , Phosphates , Carbonates , Adsorption , Anti-Bacterial Agents , Calcium CarbonateABSTRACT
The effect of acetone on temporal oscillations and spatio-temporal patterns occurring in the ruthenium-catalyzed Belousov-Zhabotinsky (BZ) reaction was investigated in a closed batch system. The periods of temporal oscillations and waves significantly decrease with increasing acetone concentration. At low concentrations of acetone (0.01-0.05 M), regular wave patterns are observed with prolonged lifetimes of both temporal oscillations and waves. However, for higher concentrations (0.10-1.00 M acetone), the lifetime is shortened and irregular patterns are formed. The photosensitivity of waves of the Ru(bpy)3(2+)-catalyzed BZ reaction remains the same for all acetone concentrations. The results are discussed in terms of the proposed reaction mechanism.
ABSTRACT
CONTEXT: Isoniazid (INH) is one of the medications most used for tuberculosis (TB) treatment. However, long-term continuous therapy can cause hepatotoxicity and peripheral neuritis. The degradation of INH is an important aspect of the research in the field of drug stability as well as drug formulation for controlling release. It is thought that tautomerization, hydrolysis as well as nucleophilic substitutions can cause decrease in INH as non-enzymatic degradation. Therefore, it is crucial to understand the mechanisms and energies of the major reactions in order to provide reference for future drug formulation and application. This study is an effort to understand the kinetic and thermodynamic properties of the non-enzymatic degradation reactions. The chemical reaction phenomena are investigated using the density functional theory (DFT) method. This study shows that major degradation of INH can be done via tautomerization followed by hydrolysis. The general trends in nucleophilic degradation presented here are consistent with experimental pKa of nucleophiles. METHODS: All DFT calculations were performed using the Gaussian Software Packages (Gaussian 09 revision B.01 and GaussView 5.0.8). MOLEKEL 4.3 software was utilized to visualize the molecular graphics of all relevant species. The optimized molecular geometries were calculated using B3LYP/6-311 + G(d,p) level in the gas phase. The IEF-PCM/B3LYP/6-311 + G(d,p) level was selected for single-point and frequency calculations in aqueous media.
Subject(s)
Antitubercular Agents , Isoniazid , Density Functional Theory , Hydrolysis , KineticsABSTRACT
A simple method to prepare phosphate/carbonate composites for use as porous sponge-like phosphate fertilizers (ps-PO4Fs) is presented. The composites ps-PO4Fs were prepared by ion-exchange implantation of phosphate onto the surface of vaterite-phase calcium carbonate (CaCO3) microparticles. The ps-PO4Fs obtained under the optimized conditions were found to contain a nanoscale porous network of calcium phosphate covering the CaCO3 support. In addition, ps-PO4Fs exhibited two distinct phosphate release modes having different kinetics: a fast-release step over the initial 24 h period following a parabolic diffusion model, indicating controlled diffusion from external surfaces/edges, and a second slow-release step over the course of a month following the Ritger-Peppas model, indicating the release and diffusion of phosphate adsorbed at specific sites. The ps-PO4Fs also adsorbed glyphosate well because of their porous structure and large surface area. However, glyphosate adsorption prevented phosphate release at concentrations greater than 10 mg L-1. The ps-PO4Fs were tested for their effects on plant growth and showed effects similar to commercial fertilizers. In summary, these smart, eco-friendly, and multifunctional fertilizers having two-stage phosphate release could enable the application of lower amounts of fertilizer and remove excess glyphosate from the environment.
ABSTRACT
An alternative approach using visible chemical waves for ethanol determination is presented. The method is based on the dynamic change of chemical waves in the Belousov-Zhabotinsky (BZ) reaction by perturbation with ethanol. The observablepropagating waves, generatedina Petri dish, can be recorded by using a smartphone camera. The propagating distances are measured from photographic images and then plotted as a function of time to attain the wave velocity. It is found that wave velocities are inversely proportional to ethanol concentrations. By using this linear relationship, the ethanol content can be efficiently quantified with good intra-day and inter-day precision (<3% RSD). Validated by the GC technique, the developed method is highly reliable and successfully applied for quantifying the ethanol content in beer, colored whisky, and vodka samples. Hence, this new method provides an alternative practical strategy for simple quantitative detection of ethanol without the need for instruments.