Corrosion inhibition studies of cashew nut (Anacardium occidentale) on carbon steel in 1.0 M hydrochloric acid environment

The corrosion inhibitive characteristics of the cashew nut (Anacardium occidentale) were studied as an eco-friendly green corrosion inhibitor at ambient temperature of 25 °C using weight loss analysis and adsorption isotherms. The effect of inhibitor concentration (4–12 g/l) at immersion time of 3–12 days was evaluated. The inhibitive ability of cashew nut shows a significant inhibition efficiency of 86% at 12 g/l concentration for 3-days and 72.9% at 12-days, which are undoubtedly as a result of the absorption of the inhibitor molecules on the metal surface which serve as a barrier against corrosion of carbon steel in acidic medium. The adsorption mechanism was found to fit Tempkin isotherms. The average optimum free energy of absorption was calculated to be −17.374 kJ mol–1 indicating that the process was exothermic and physisorption

Electrocrystallisation and recovery of gold from thiosulphate-sulphite aged electrolyte

Interest has grown in developing non-toxic electrolytes for gold electrodeposition to replace the conventional cyanide-based bath. The main driver for the development of this electrolyte is the long term sustainability. One electrolyte that is being examined is a solution containing thiosulphate and sulphite, which has been developed specially for microelectronics applications. However, at the end of the electrodeposition process, the spent electrolyte can contain a significant amount of gold in solution and low concentration in rinse waters. Since the discharge of gold along with the effluent is a major economic as well as environmental concern, this study has been initiated to investigate if gold can be recovered from a spent thiosulphate-sulphite electrolyte. The recovery process is expected to have an enhanced value if the recovered gold can be tailored for suitable applications, for example, gold nanoparticles are useful in catalysis, sensors, electronics etc. In the initial work, we have used flat-plate glassy carbon and graphite electrodes to study the mechanism of nucleation and crystal growth of gold deposition from concentrated spent electrolyte. It was found that at the early stages of reduction process, the deposition of gold on glassy carbon exhibits an instantaneous nucleation of non-overlapping particles. At longer times, the particles begin to overlap and the deposition follows a classic progressive nucleation phenomenon. On the other hand, deposition of gold on graphite does not follow the classical nucleation phenomena. Microscopy observations demonstrate that the particle size and density of the deposited gold can be controlled by varying the deposition potentials and time. A flow cell operated in a flow-by mode was constructed which used a threedimensional reticulated vitreous carbon to recover gold from rinse waters. The reactor was tested by removing copper (II) from acidified copper sulphate solution near the mass transfer limiting rate. The gold removal process was then operated close to mass transport control at all times by adjusting the current to its limiting value, 1L(t). It was found that the gold concentration depletes very slowly with time owing to the changes in electrolyte.EThOS - Electronic Theses Online ServiceMinistry of Science, Technology and Innovations (MOSTI), Malaysia : Short Term Scientific Mission (STSM) grant from COST D19-00935GBUnited Kingdo

Inhibitive effect of Cocon nucifera L. (coconut pulp) extract on mild steel acid corrosion

In recent years, industrial sectors are concerned with the corrosion of metal and alloys and they also received huge attention from researcher to overcome these problems. To decelerate the rate of corrosion or to stop the corrosion to occur, one of the common methods to deal with this problems is using green inhibitor. The use of local wastes which are organic in nature for the production of green corrosion inhibitor is no doubt the trend of the day. To arrive at an inexpensive non-toxic, eco-friendly inhibitor formulation, the present study on the use of coconut pulp waste extract of Cocon Nucifera L. has been carried out by the weight loss method. The aim of this project is to study the inhibitive effect in terms of time and concentration of the coconut pulp waste extract on the acid corrosion of mild steel in 1.0 M HCL solution. Result showed that the inhibition efficiency was found to increase with increasing inhibitor concentration up to maximum 94.52% for 10 %v/v at 48 hours immersion time. Examination on the extract by Fourier transform infrared spectroscopy (FTIR) confirms that the extract contains functional group of N-H, O-H, C-H, C≡C, C=O, C=C, C-F and C-O that good for corrosion inhibitor while scanning electron microscopy (SEM) studies showed that the deposition of coconut pulp extract on the metal surface. The results of all studies confirmed that the extract of coconut pulp has great potential to prevent the corrosion of mild steel in acidic environment with highest % IE is 94.52 % and the corrosion rate is 3.6919 x10-5

CH4 and CO2 detection by using carbon nanotube-based sensors

This research was carried out to investigate the effect of gas adsorption towards the electrical resistance of carbon nanotubes (CNTs) thin film. CNTs were synthesized by Floating Catalyst Chemical Vapor Deposition (FC-CVD) method on quartz substrate at 950°C under methane gas flow rate of 150 Standard Cubic Centimeters per Minute (SCCM). Then, the electrical resistance of CNTs was measured by exposing the sensors to CO2 and CH4 gases operating at room temperature. The sensors showed high responses to the gaseous molecules. In the same experimental conditions, the recovery of the sensors was different for CO2 and CH4. It was also observed that the CNTs device behaves as a p-type semiconductor when exposed to gaseous molecules. The fabrication process was relatively simple and did not require special techniques

The effect of CH4 and CO2 exposure on carbon nanotubes electrical resistance

This research was carried out to monitor and investigate the gas sensing effects on carbon nanotubes (CNTs) by a systematic study of the variations in the electrical resistance as sensor signal induced by adsorption of CO2 and CH4 gaseous molecules. The CNTs were synthesized by Floating Catalyst Chemical Vapor Deposition (FC-CVD) method on quartz substrate under benzene bubble at temperature of 700°C. Then, they were tested for gas sensing applications operating at room temperature. Upon exposure to gaseous molecules, the electrical resistance of CNTs dramatically increased for both CO2 and CH4 gases with short response time and high sensitivity. It was also observed that the CNTs device behaves as a p-type semiconductor when exposed to gaseous molecules. In addition, the recovery of the sensors and mechanism of gas sensing procedure are discussed

Recovery of heavy metals from spent etching waste solution of printed circuit board (PCB) manufacturing

The process of etching is the most crucial part of the work of manufacturing printed circuit boards (PCB). In the etching process by nitric acid, a spent etching waste solution of composition 250 g/L HNO3, 30-40 g/L Cu, 30-40 g/L Sn, 30-40 g/L Pb and 20-25 g/L Fe is produced. High metal concentrations in the spent etching waste solution make it a viable candidate for the recovery of metals. Recovery of metals from spent etching waste solution is a significant concern as the recent growth in production of printed circuit boards has generated a drastic increase of spent etching waste solution each year. This study concerns itself with the recovery of metals from spent etching waste. In this study a dilution was made in order to increase the pH of the solution as spent etching waste solution has high acidity, and the electrowinning method was performed to recover metals from the spent etching waste solution. Glassy carbon and platinum were used as cathode and anode in order to investigate the electrodeposition of metals and cyclic voltammetry investigation suggests that the deposition of metals on glassy carbon electrodes occurs at four different overpotentials mainly at -0.15 V, -0.35 V, -0.45 V and -0.75 V. Microscopy observation demonstrates that there is a deposition of metals by applying the potentials in a set of current-time transient study for a duration of 60 seconds and the metals recovered formed as aggregates

Optimization of a method to extract the active coagulant agent from jatropha curcas seeds for use in turbidity removal.

An improved and alternative method for the extraction of the active coagulant agent from Jatropha curcas seeds was developed and compared with the conventional water extraction method (JCSC-DW). In the new method, the seeds were extracted using different solvents in different concentrations, using NaCl (JCSC-NaCl) and NaOH (JCSC-NaOH) to extract the active coagulant agent from the Jatropha. In addition, ultrasound was investigated as a potential method to assist the extraction process. Batch coagulation experiments were conducted to evaluate the performance of the extracted coagulant achieved through various schemes. The effects of the dosage, pH and concentration of solvents were investigated for optimum turbidity removal at different values of initial synthetic wastewater turbidity from 50 to 500 NTU. JCSC-NaCl at 0.5 M was found to provide a high turbidity removal of >99% compared to JCSC-DW and JCSC-NaOH at pH 3 using 120 mg/l of the coagulant agent. Among these three solvents, NaOH demonstrated the lowest performance in turbidity removal. The conventional extraction method of the active coagulant agent by blending the seeds in solvents for 2 min alone sufficiently extracts most of the coagulant component from the Jatropha seed and provides up to 99.4% turbidity removal. Blending assisted by ultrasound demonstrated comparable turbidity removal in a shorter period of time and thus showed a potential to be used on a larger scale. Analysis was undertaken to determine the protein content as this is believed to be the coagulating agent. It was found that extraction of the coagulant agent using NaCl yielded more protein compared to when using water and NaOH

Concentration profile behavioral from digestate television printed circuit board for metal recovery via electrolysis

The production of electric and electronic products is one of the fastest growing businesses in the world. This scenario creates increasing amount of electric and electronic waste in our waste stream and it becomes a common problem facing by the world. In this study, the concentration profile behavioral of a television printed circuit board (PCB) is being investigated for future electrolysis treatment. Prior to that, a PCB is cut into several pieces and is digested via aqua-regia. The digestate from the digestion is analyzed using Inductively Coupled Plasma (ICP-MS) to estimate the present of metals with their range of corresponding concentration value and Thermogravimetric Analysis (TGA) is carried out to investigate the thermal decomposition of the filtrate from the digestion. The major metal elements that contain in the digestate are Cu (3,123-6,994 mg L-1), Pb and Fe and traces of two precious metal namely (6.3-13.8 mg L-1) and Au (0.2-5.4 mg L-1). Three degradation stages are observed in the TGA analysis (two days after ovenate at 102°C) namely moisture removal with 10.3 wt %, volatile matters removal with 14.45 wt.% and non-volatile removal with 16.7 wt%. The ash value after 1000oC heating in the TGA is almost 60 wt. %. An electrolysis process is then proposed in order to recover selectively valuable metals, such as Cu, Pb, Ni, Ag and Au

Research trend in the processing and application of macroporous ceramic components

Porous ceramic components with decently controlled porosity offers remarkable advantages in industrial and structural applications such as fluid filtration, thermal insulation and scaffolds for bone tissue engineering. In this review study of porous ceramic components, requisite processing techniques necessary for the development of porous ceramics with imbued microstructural model intended for a specific application. An appraisal of the fabrication was made with respect to their economic viability wherein cost effective methods having great potentials in decently controlling the pore network imbued within the host ceramic matrix was preferred over the capital intensive counterparts

Magnetic field enhanced electrocoagulation using iron electrode in removing glyphosate from aqueous solution

The widespread use and high solubility nature of glyphosate posed a significant threat to water contamination. Glyphosate is a non-selective herbicide for weed control in various agricultural applications. Electrocoagulation method was thus proposed to coagulate this pollutant, and a magnetic treatment was introduced to shorten settling time and to assist sedimentation of suspended solids. The effects of operational variables such as initial glyphosate concentration, electrolysis time and applied voltage towards removal of glyphosate, chemical oxygen demand (COD) and total suspended solids (TSS) were explored to broaden the core understanding of settling velocity and ferromagnetic effects of magnetic fields. The combination of electrocoagulation and the magnetic field was designed and setup into batch laboratory experiment and static mode with two parallel iron (Fe) plates for both anode and cathode. This design used permanent magnets namely NdFeB of 0.55 T and the magnetic exposure time was 6 h. Results showed that the increment in both applied voltage and treatment time and the reduction in initial glyphosate concentration were beneficial for improving glyphosate, COD, and TSS removal efficiencies. An initial glyphosate concentration of 25 mg/l, applied voltage of 30 V and treatment time of 40 min, were obtained as optimum experimental conditions. Respective glyphosate, COD and TSS removal efficiencies of 95.84%, 71.43%, and 79.08% were observed in experiments conducted in optimum conditions. As a conclusion, magnetic field strongly encouraged electrocoagulation process in obtaining better results due to a ferromagnetic mechanism in aqueous solutions