Methylene Blue Dye Adsorption from Wastewater Using Hydroxyapatite/Gold Nanocomposite: Kinetic and Thermodynamics Studies

The present work demonstrates the development of hydroxyapatite (HA)/gold (Au) nanocomposites to increase the adsorption of methylene blue (MB) dye from the wastewater. HA nanopowder was prepared via a wet chemical precipitation method by means of Ca(OH)2 and H3PO4 as starting materials. The biosynthesis of gold nanoparticles (AuNPs) has been reported for the first time by using the plant extract of Acrocarpus fraxinifolius. Finally, the as-prepared HA nanopowder was mixed with an optimized AuNPs solution to produce HA/Au nanocomposite. The prepared HA/Au nanocomposite was studied by using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray Analysis (EDX) analysis. Adsorption studies were executed by batch experiments on the synthesized composite. The effect of the amount of adsorbent, pH, dye concentration and temperature was studied. Pseudo-first-order and pseudo-second-order models were used to fit the kinetic data and the kinetic modeling results reflected that the experimental data is perfectly matched with the pseudo-first-order kinetic model. The dye adsorbed waste materials have also been investigated against Pseudomonas aeruginosa, Micrococcus luteus, and Staphylococcus aureus bacteria by the agar well diffusion method. The inhibition zones of dye adsorbed samples are more or less the same as compared to as-prepared samples. The results so obtained indicates the suitability of the synthesized sample to be exploited as an adsorbent for effective treatment of MB dye from wastewater and dye adsorbed waste as an effective antibacterial agent from an economic point of view

Synthesis of Biodegradable <i>Gum ghatti</i> Based Poly(methacrylic acid-aniline) Conducting IPN Hydrogel for Controlled Release of Amoxicillin Trihydrate

<i>Gum ghatti</i>-<i>graft</i>-poly­(methacrylic acid-aniline) interpenetrating network (IPN) hydrogel was prepared by a two-step aqueous polymerization method. First, poly­(methacrylic acid) (poly­(MAA)) chains were graft co-polymerized onto a <i>Gum ghatti</i> (Gg) backbone via free radical polymerization. Different reaction conditions were optimized in order to incorporate maximum water uptake capacity of the synthesized hydrogel. The synthesized hydrogel network showed a pH-dependent swelling behavior. Second, aniline (ANI) monomer was penetrated through the preformed Gg-<i>g</i>-poly­(MAA) network by simple oxidative polymerization method. The homogeneity and distribution of different ions of the cross-linked hydrogels were investigated by the time-of-flight–secondary-ion mass spectrometry chemical imaging technique, and a correlation analysis by color overlay and scatter plot technique. The resulting cross-linked hydrogels’ structure, morphology, and thermal behavior were investigated. Biodegradation studies of the cross-linked hydrogel samples were carried out by composting soil test for a period of 60 days. The evidence for biodegradability has been confirmed by carrying out the scanning electron microscopy technique. The release profiles of the hydrogel networks were investigated through amoxicillin trihydrate model drug under different pH conditions at 37 °C. Drug release through the Gg-<i>g</i>-poly­(MAA) matrix was found to show non-Fickian behavior at pH 2.2 and 7.0, whereas, a Fickian mechanism was exhibited at pH 9.2. On the other hand, Gg-<i>g</i>-poly­(MAA-IPN-ANI) matrix exhibited Fickian behavior at each pH media. The hydrogel networks showed less release in acidic and neutral media than in basic media, suggesting that hydrogels may be suitable drug carriers for colon specific controlled release of drug delivery in the lower gastrointestinal tract