Simultaneous Adsorption of Aqueous Pb2+, Cu2+, Zn2+, and Cd2+ Using Surfactant-Modified and Unmodified Activated Carbon in a Fixed Bed Column

The goal of this work is to improve the simultaneous removal of Pb2+, Cu2+, Zn2+, and Cd2+ ions from synthetic wastewater in a fixed bed column by incorporating sodium dodecyl sulfate (SDS) onto the surface of activated carbon made from coconut shells. The activated carbons were characterized using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy-energy dispersive x-ray (SEM-EDX). The adsorption column dynamics were studied by varying the flow rates (5, 10 and 15 mL/min), bed heights (10, 15 and 20 cm), and initial concentrations (50, 150, and 250 mg/L). The activated carbon has a pore volume of 0.715 cm3/g and a BET-specific surface area of 1410 m2/g. Sodium dodecyl sulfate (SDS) surfactant incorporation onto the surface of the activated carbon enhances its capacity for simultaneous adsorption of Pb2+, Cu2+, Zn2+, and Cd2+ from the aqueous medium. The affinity of the heavy metals to both unmodified (AC) and modified (AC-SDS) activated carbons followed the order of Pb2+ > Cu2+ > Zn2+ > Cd2+. The dynamic adsorption of the column depends on the flow rate, bed height, initial metal concentration, and SDS surface modification. With a 5 mL/min flow rate, a 20 cm bed height, and a 50 mg/L initial metal concentration, a maximum break-through time of 150 minutes for the unmodified activated carbon (AC) and 180 minutes for the SDS-modified activated carbon (AC-SDS) was reached.

Atmospheric Corrosion Studies of Ductile Iron and Austenitic Stainless Steel in an Extreme Marine Environment

This paper presents the corrosion characteristics and the accompanying changes in the microstructure of unalloyed duc-tile iron (DI) and austenitic stainless steel (ASS) in table salt medium representing an upper limit in an extreme marine environment. The individual corrosion rates of DI and ASS was evaluated for the maximum time period of 1200 hr. Using the immersion test technique, the corrosion rate of DI was evaluated and found to be four-orders of magnitude greater than that of ASS. The corrosion product morphologies of the DI showed that the nodular matrix was gradually covered up as immersion time progressed while the corrosion channels and volume of pits that initially formed in ASS respectively deepened and increased with increased exposure time. This work is important as a reference point for the quantification of the corrosion effectiveness of alloying DI. The microstructures of the corroded samples showed corro-sion initiation and gradual accumulation of corrosion products.

Comparison of the ICRP 60 and ICRP 103 Recommendations on the Determination of the Effective Dose from Abdominopelvic Computed Tomography

The effective dose takes into consideration the amount of absorbed dose received by tissues, individual organs and also organ’s radiosensitivity. This study concentrates on the Commission’s regulations of 1991 and 2007 tagged ICRP 60 and ICRP 103 respectively, and seeks to suggest the better guideline for determination of detriment to patient especially from abdominopelvic computed tomography. With mean totals of 375.0 mSv for the ICRP 60 and 341.3 mSv for the ICRP 103 obtained from abdominopelvic computed tomography involving 20 different patients, a T-test calculated value of 6.716 was obtained and compared with the value in the T-table at 95% confidence limit and 18 degrees of freedom to confirm whether there is a significant difference in both ICRP 60 and 103 recommendations in the determination of the effective dose. Finally, it is concluded that there is a significant difference in the ICRP 60 and ICRP 103 as fewer effective doses are obtained from the ICRP 103 recommendations and this difference verifies that the ICRP 103 is more suitable for the determination of the effective dose.

Numerical Analysis of Thermo-Elastic Contact Problem of Disc Brakes for Vehicle on Gradient Surfaces

In this study, the thermo-elastic effects of frictional heat generation in a disc brake system due to braking actions were simulated. The mathematical model that defined the problem was developed from the kinetic and potential energies of moving vehicles on the gradient surfaces. This problem was solved for the selected geometry of disc brake and pad with their material properties selected from existing literatures using the finite element method and the computational results were obtained. The thermal deformation obtained was in good agreement with similar literature results. Also, for the same braking period and conditions, the results showed that a vehicle ascending a hill gave a higher temperature rise, Von Mises stress and thermal deformation on brake contact surfaces than when descending hill. Therefore, the braking period required to bring a moving vehicle in ascendent motion to a lower speed is expected to be shorter because of the gravity effect than horizontal motion, while descendent motion requires longer braking period.

Development of an Environmentally Friendly in-situ Pack-Cyaniding Technique

A safe and environmentally friendly cyaniding method has been developed to mitigate the toxic impacts of cyanide salts on the environment during conventional cyaniding. The method entails in-situ diffusion of nascent cyanide from mature cassava leaves into the surface of mild steel components via pack-cyaniding. Both high-temperature in-situ diffusion into austenite and low-temperature in-situ diffusion into ferrite were explored. Results from light and scanning electron microscopic studies showed that surface hardness of the steel components was substantially increased. The waste product was a harmless biodegradable organic compound that posed no disposal threats. This study is important for increasing the wear resistance of ferrous parts for a longer service life in application without polluting the environment.

Comparative Study of Corrosion Sensitivity of Selected Ferrous Metals in Crude Oil

Corrosion characteristic of selected ferrous metal samples (plain and alloyed ductile iron, low carbon steel and austenitic stainless steel) in crude oil was investigated using weight loss method. The microstructures of the coupons were taken before and after corrosion test. It was observed that all the materials experience gain in weight within the first 10 days in the medium. This weight gain is attributed to the formation of hard and passive phases which acted as strong protective barriers to corrosion. It was also observed that the rate of corrosion decreased with increase in the number of days of exposure for all the coupons, this may be probably due to the deposition of corrosion products that tend to shield the corroding surface from further corrosion attack, there by depressing the rate of corrosion. This result shows that despite initial low corrosion resistance of plain ductile iron, it can still be considered, alongside other materials, for application in pipelines and storage facilities for crude oil.

Evaluation of the Compressive Strength of Hybrid Clay Bricks

This work has presented the evaluation of the compressive strength of hybrid clay bricks from interlocking brick making machine. The mixture of clay and cement at varying proportions was loaded into the mould compartment, mechanically rammed and hydraulically controlled. The raw clay was sourced from Ilesa and Akure in the south-western part of Nigeria. The results showed that when the cement content was 6%, the highest compressive load and energy at break were obtained in hybrid bricks from both Ilesa and Akure samples. However, the optimum service performance under compressive loading was attained at 6% cement in Ilesa hybrid bricks. Ilesa hybrid bricks possess better reliability and workability under loading than the Akure bricks.

Application of Geophysical Methods to Building Foundation Studies

A geophysical survey involving the electrical resistivity method utilizing the Vertical Electrical Sounding (VES) and Electrical Imaging Techniques was conducted around the premises of an area within south-western Nigeria with the aim of studying structural defects which may be responsible for future problems and characterizing the soil conditions of the site. A total of 15 VES stations were occupied using Schlumberger Configuration with AB/2 varying from 1 to 65 m. In the electrical imaging, dipole-dipole array was adopted and the two traverses were occupied in the S-N and E-W directions close to where wall cracks and subsurface problems were manifested. Five main geoelectric sequences were delineated within the study area;these include the topsoil (clay and sandy clay), lateritic clay, weathered bedrock (clay, sandy clay and clayey sand), fractured bedrock and fresh basement. A major discontinuity (fracture zone) was discovered along the S-N direction, while a weak zone was also discovered along E-W direction. The result of this research has shown that the causes of the cracks and distress on the walls within the site may have been influenced by the differential settlement resulting from the incompetent subsoil materials and the fractured bedrock on which the foundation of the building was laid.