Effect of operational parameters, characterization and antibacterial studies of green synthesis of silver nanoparticles using Tithonia diversifolia

Background: There is a growing interest in the green synthesis of silver nanoparticles (AgNPs) using plant extract because the technique is cost effective, eco-friendly and environmentally benign. This is phasing out the use of toxic and hazardous chemical earlier reported. Tithonia diversifolia is a wild sunflower that grows widely in the western part of Nigeria with a proven medicinal benefit. However, several studies carried out have left doubts on the basic operational parameters needed for the green synthesis of AgNPs. The objective of this work was to carry out green synthesis of AgNPs using T. diversifolia extract via an eco-friendly route through optimization of various operational parameters, characterization, and antimicrobial studies. Method: Green synthesis of TD-AgNPs was done via bottom-up approach through wet chemistry technique using environmentally benign T. diversifolia plant extract as both reducing and stabilizing agent. Phytochemical Screening of the TD plant extract was carried out. Experimental optimization of various operational parameters—reaction time, concentration, volume ratio, and temperature was investigated. TD-AgNPs were characterized by UV–Vis spectroscopy, FTIR Spectroscopy, SEM/energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Antimicrobial studies against multi drug resistant microorganisms (MDRM) were studied using the agar well diffusion method. Results: This study reveals the importance of various operational parameters in the synthesis of TD-AgNPs. Excellent surface plasmon resonance peaks (SPR) were obtained at optimum experimental factors of 90 min reaction time under room temperature at 0.001M concentration with the volume ratio of 1:9 (TD extract:Ag ion solution). The synthesis was monitored using UV– Vis and maximum wavelength obtained at 430 nm was due to SPR. The morphology and elemental constituents obtained by TEM, SEM, and EDX results revealed a spherical shape of AgNPs with prominent peak of Ag at 3.0 kV in EDX spectrum. The crystallinity nature was confi rmed by XRD studies. FTIR analysis proved presence of biomolecules functioning as reducing, stabilizing, and capping agents. These biomolecules were confi rmed to be fl avonoid, triterpenes, and saponin from phytochemical screening. The antimicrobial studies of TD-AgNPs were tested against MDRM— Escherichia coli, Salmonella typhi, Salmonella enterica, and Bacillus subtilis. Discussion: The variation of reaction time, temperature, concentration, and volume ratio played substantive and fundamental roles in the synthesis of TD-AgNPs. A good dispersion of small spherical size between 10 and 26 nm was confirmed by TEM and SEM. A dual action mechanism of anti-microbial effects was provided by TD-AgNPs which are bactericidal and membrane-disruption. Based on the antimicrobial activity, the synthesized TD-AgNPs could find good application in medicine, pharmaceutical, biotechnology, and food science

Kinetics and Thermodynamics of Adsorption of Rhodamine B onto Bentonite Supported Nanoscale Zerovalent Iron Nanocomposite

Bentonite clay supported nanoscale zerovalent iron (BC-nZVI) composite was successfully prepared. BC-nZVI was characterized by physicochemical and spectroscopic techniques. Surface area as determined by sear’s method is 291.2 cm2 . Adsorption operational parameters were investigated in a batch technique. At 500 mg/L initial concentration, 120 minutes contact time and pH 3, 454.81 mg/g quantity was adsorbed. The highest adsorption percentage removal efficiency was obtained at room temperature. Kinetic data fitted best to pseudo second order and the mechanism was diffusion governed. The kinetic models were further validated by sum of square error (SSE) and non-linear Chi-square statistical models (X 2). The values of the thermodynamic parameters: standard enthalpy change ΔH (- 10.597 Jmol -1 )to (-5558 Jmol -1.), standard entropy change, ΔS (-277.804 J mol -1 K -1 )- to (-139.2595 J mol - 1 K -1) and the Gibbs free energy (ΔG) revealed that the adsorption process was feasible, spontaneous and exothermic in nature. The performance of BC-nZVI enlisted it as a great potential adsorbent for effective removal of Rhodamine B and therefore recommended for application in industrial effluent treatment

Kinetics and isotherm modeling of adsorption of rhodamine B dye onto chitosan supported zerovalent iron nanocomposite (C-nZVI)

The kinetics and isotherm modeling of adsorption of Rhodamine B (RhB) Dye onto chitosan supported zerovalent iron nanocomposite (C-nZVI) was successfully studied in a batch technique. The quantity adsorbed increased with increase in initial concentration from 49.33 mg – 242.37 mg for 200 ppm to 1000 ppm and high percentage removal efficiency (%RE) of 99.72% attained at 90 minutes contact time. Equilibrium data were analyzed by six isotherm models: Langmuir, Freundlich, Temkin, Dubinin-Kaganer-Raduskevich (DKR), Redlich-peterson and Halsey isotherm model. Equilibrium data best fitted to Freundlich isotherm supported by Halsey isotherm model. Langmuir monolayer adsorption capacity (256.41 mg/g) of C-nZVI obtained greater than most adsorbent reported for adsorption of RhB. The mean adsorption free energy, E per molecule evaluated from DKR model was less than 8 KJmol -1 indicating a physisorption mechanism. The kinetic data best fitted to pseudo second-order kinetic model as validated by sum of square error (SSE) statistical model and the mechanism controlled by pore dif usion. The study revealed the great potential of C-nZVI for ef ective removal of RhB dye. C-nZVI is therefore recommended for civic and industrial ef luents treatment