Band 236, Heft 9

In fresh water, aluminum cannot be used as a galvanic anode for the cathodic protection (CP) system because the accumulation of oxide films causes the electrochemical potential to change to an extremely noble potential (passivation). To work correctly, aluminum anodes often require chloride ions in the electrolyte. Because impressed current anodes are fairly inert, the anode component corrodes at an extremely low rate. The present case study focused on a novel strategy for employing aluminum anode as an impressed current anode for cathodic protection inside a fresh water storage tank made of X65 steel. According to the impressed current scenario, 0.6 A of current supply and 0.33 V of voltage were required to properly protect the X65 steel tank’s internal surface area of 421 m 2 . Prior to the implementation of cathodic protection, the potentials varied from −0.474 to −0.509 V (vs. Ag/AgCl). After 30 days, 60 days, and 90 days of cathodic protection, the potential values inside the protection zone showed a significant change (−0.800 and −1.150 V vs. Ag/AgCl). The results demonstrate that aluminum anodes with a considerable performance (current capacity) and a minimal consumption level can really be employed as impressed current anodes in fresh water applications.

The paper deals with the thermal decomposition of organometallic compound ferrocene carboxaldehyde [(C 5 H 4 CHO)Fe(C 5 H 5 )] in oxidative atmosphere, which leads to pure hematite nanoparticles, studied with non-isothermal thermogravimetry (TG) protocol. Deconvolution method with Fraser-Suzuki fit function is adopted to resolve the complex multistep TG profiles into six different reaction steps. Step-wise reaction kinetic parameters (activation energy, reaction mechanism function, reaction rate) are estimated based on the mathematical analysis of the multi-heating rate TG data primarily following model-free (integral isoconversional) approach and using master-plot method. The estimated kinetic parameters are utilised to reconstruct the conversion plots which successfully resemble the experimentally observed ones. A plausible reaction process leading to hematite on thermal decomposition of ferrocene carboxaldehyde as the end product is discussed. A comparative discussion on the thermal decomposition of two ferrocene derivatives have been made. The novelty of the present work lies in successful deconvolution of complex TG profiles and hence obtaining the step-wise reaction kinetic parameters demonstrating different reaction mechanisms involved in the thermal synthesis of hematite nanoparticles starting from ferrocene carboxaldehyde which have no prior reporting. Further, a satisfactory agreement between the reconstructed and experimental decomposition profiles establishes the correctness of the applied modelling approach as well as the methodology adopted.

The kinetics of polypropylene pyrolysis has been studied under isothermal and non-isothermal conditions using Arrhenius and Kissinger–Akahira–Sunose (KAS) equations. Under isothermal conditions, applying first order kinetic model, activation energy ( E a) and pre-exponential factor ( A ) were investigated and observed as 119.7 kJ mol −1 and 1.2 × 10 10  min −1 , while in case of non-isothermal kinetics using Kissinger–Akahira–Sunose method, the average E a and A were found to be 91.23 kJ mol −1 and 2.3 × 10 7  min −1 , respectively. A comparison among the isothermal and non-isothermal reactions was made on the basis of kinetics parameters. The results from both the methods showed trivial variation in kinetic parameters of the pyrolysis reaction which may be due to two major reasons. Firstly, the selection of the kinetic model applied and secondly the inconsistency due to various experimental conditions used which can be reduced at optimized conditions. As the disposal of plastic materials need reliable kinetics information to model their decomposition reactions, therefore, the kinetics data thus obtained from pyrolysis reaction of model polypropylene will help in the utilization of polypropylene waste as energy source on industrial scale.

In the present investigation, silver nanoparticles were synthesized and a comparative analysis was performed of modified Turkevich and BRUST methods. Silver nitrate precursor was reduced by trisodium citrate dihydrate and ascorbic acid was used as a surfactant. Based on Turkevich and BRUST methods, the process variables, i.e., temperature, reducing agent concentration, stirring speed, mode of injecting reducing agent/precursor to large excess volume of either precursor/reducing agent were studied. The size of the particles was preliminarily ascertained by DLS studies and it was found that modified BRUST method yielded silver nanoparticles with average particle size of 25 nm, while modified Turkevich method furnished nanoparticles with average particle size of 15 nm. The silver nanoparticles were characterized by employing the UV/visible, Zeta sizer, scanning electron microscopy (SEM) and energy dispersive microscopy (EDX) techniques. Results revealed that the silver nanoparticles size can be controlled by optimizing the conditions of modified Turkevich and BRUST methods.

The present study focuses on iron nanoparticles (Fe NPs) biosynthesis, characterization and photocatalytic activity (PCA) appraisal for methylene blue dye degradation. A green rapid biogenic synthesis route was employed for synthesis of Fe NPs using banana peel extract. The synthesized Fe NPs was characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy) and EDX (energy dispersive X-ray) techniques. These analysis confirmed the synthesis of zero valent Fe NPs with high crystallinity, purity and semi spherical in shape. The photocatalytic activity was assessed under ultra violet irradiation and under optimum conditions, 87% degradation of MB dye was obtained for 72 min of irradiation, which revealed promising catalytic efficiency of the Fe NPs. The result shows that photocatalytic activity of Fe NPs is promising and could possibly be used to treat dyes in industrial effluents and the use of green synthetic protocol is suggested due to its ecofriendly nature.

In the present study, biological method was opted to synthesize ZnO NPs from Rumex dentatus plant. 0.1 M solution of zinc nitrate hexahydrate is mixed with the aqueous solution of R. dentatus plant leaves extract. The proportion of each solution was 1:1. Extract of plant leaves act as reducing agent. Firstly, the color changed from dark green to brown was observed and precipitates of light brown color appeared. Characterization of produced ZnO NPs was done using UV–Visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-rays (EDX) and X-ray diffraction (XRD) spectroscopy. The prepared ZnO NPS shows maximum absorption at 373 nm, in UV–Visible range. The shape of synthesized ZnO NPs is displayed by SEM. XRD analysis explains the average size of NPs is 6.19 nm. EDX tells about the percentage composition of synthesized ZnO NPs. Antibacterial analysis declared the NPs as good antibacterial agents. Photocatalytic activity of ZnO NPs was done using methyl orange dye. It was concluded that ZnO NPs can degrade toxic pollutants especially dyes.

Most of the transition metal ions are toxic and their removal from water is important. For this purpose, nearly monodisperse spherical core shell microgel particles with diameter of 88 ± 3 nm have been synthesized by free radical precipitation polymerization method and characterized by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Extraction of copper ions from water under several conditions of pH, copper ions content and core shell microgel concentrations was undertaken. Several adsorption isotherms were tested to explore the process of adsorption of copper ions on the microgel particles. Kinetics of adsorption process was examined by pseudo first order, pseudo second order, intra-particle diffusion and Elovich models. Copper ions adsorbed in shell region of core shell microgel were reduced to copper nanoparticles. The hybrid microgel was used to reduce organic pollutants such as 4-nitrophenol (4NP), methylene blue (MB), and methyl orange (MO) in aqueous medium. The value of pseudo first order rate constant for catalytic reduction of 4NP, MB, and MO was found 0.602, 0.831, and 0.874 min −1 respectively. The resultant core shell hybrid microgel system can serve as efficient catalyst for numerous other organic transformations.

Kapok fibers ( Ceiba pentandra ) were modified for the removal of copper ions from aqueous solutions through adsorption. In this fast and facile method, the polysaccharide-like groups of kapok were oxidized with potassium periodate. The novel modification is the loading of the fibers with adipic dihydrazide (ADH) which contain nitrogen and oxygen atoms for heavy metal ion binding. Adsorption experiments have been carried out and analyzed via atom absorption spectroscopy and ultraviolet/visible spectroscopy. In preliminary adsorption experiments, different kapok-based materials have been analyzed on their adsorption capacity and removal efficiency via atom absorption spectroscopy. ADH-modified fibers showed the best results and an increase of copper removal efficiency by 30% in comparison to untreated kapok fibers and superior adsorption capacity compared to kapok fibers loaded with oxalic dihydrazide (ODH). Moreover, the impact of initial concentration and contact time on the adsorption capacity and on the removal efficiency values of the ADH-modified kapok fibers has been studied. Another comparison of the ADH-modified fibers with raw kapok which was cleaned with Milli-Q water, dichloromethane and ethylene glycol showed that the new adsorbents are best suited for copper solutions with concentration values of under 10 mg/L. The heavy metal adsorption experiments were analyzed through both isotherm models Langmuir and Freundlich. The Langmuir model is found to be a suitable model for copper ions. The value of the maximum adsorption capacity is 4.120 mg/g. The ADH-modified kapok fibers were characterized with attenuated total reflection infrared (ATR-IR) spectroscopy, magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy and scanning electron microscopy (SEM).