Determination of heavy metal elements concentration in soils and tailing sediments from lateritic nickel post-mining areas in Motui District, Southeast Sulawesi

Heavy metal elements concentration study has been determined from soils and tailing sediments in laterite nickel post-mining area in Motui District Southeast Sulawesi. This study aimed to determine the concentration of some heavy metal elements, especially Fe, Co, Mn and Cr, from surface soils sediments in waste dump sites and tailing sediments in settling ponds from lateritic nickel post-mining areas. A total of 20 samples consisting of 18 soil samples and 2 tailing sediments samples were systematically collected for the study. The soil samples from the waste dump site profile were collected from 3 layers which were divided based on the colour of the soils from top to bottom, namely Layer C, Layer D and Layer E. Six soil samples were taken from each layer with space between each sample in one layer was about 50 – 60 cm. The samples were sent to the laboratory and analysed using Atomic Absorption Spectrometer (AAS) method to determine the concentration of heavy elements. Metal-bearing minerals detected from the bedrock consists of chromite, manganese, magnetite and limonite which are responsible for the Cr, Mn and Co, and Fe content, respectively. The result showed that Fe content is significantly higher in soil samples from Layer C and tailing sediments with dark red to brown in colour, suggesting the strong relation between Fe content and colour index. The general element mobility trend showed that Mn and Co are positively correlated in soil sampling from all layers and tailing samples, whereas Fe and Cr show a negative correlation trend in Layer C, D and tailing sediments but positively correlated in Layer E.

Design and technological optimization of rubber-reinforced thin-layer movable joints in the structure of a pipeline vibration-isolating compensator

Thin-layer rubber-metal elements have been widely used in various fields of technology, including helicopter construction, support parts for bridges, shock absorbers in industrial and civil construction. Their work reliability is determined by the design and technological performance features, which require experimental testing and parametric optimization. The article presents the samples and basic models testing results which were aimed at increasing the strength indicators stability of the adhesive ``rubber-metal'' joints and ensuring the failure-free operation of a rubber-metal product in the structure of a pipeline vibration-isolating compensator.

One-factor-at-a-time method combined with ICP-MS for determining 11 elements in soy sauce and their migration from the containing glass bottles

This study was designed to determine the 11 metal elements (Al, Cr, Mn, Fe, As, Ni, Cu, Zn, Cd, Sb, and Pb) in soy sauce and their migration from the containing glass bottles. Inductively coupled plasma mass spectrometry (ICP-MS) was applied for the determination of the elements and one-factor-at-a-time method was employed for optimizing the ICP-MS parameters in migration experiment and microwave digestion experiment. The developed method was successfully applied to determine the content of 11 elements. The results showed that the experiment had excellent correlation and sensitivity. The accuracy of the elements in the migration study and test of soy sauce itself ranging from 84.25% to 118.75% was satisfied, and the precision of the method was validated and the RSD was no more than 15.5%. The concentration of all the detected metal elements migrated from the glass bottles were between 0.3450 and 2.398 ng·mL−1, and the risk assessment indicated that the metal elements in soy sauce had no risk to the public health. The proposed methodology in this study was successfully applied for the quality control for metal elements in soy sauce and the containing glass bottles for the first time, and a research method suitable for soy sauce consumption process control and risk assessment has been established.

Preparation of a Novel Activated Carbon from Cassava Sludge for the High-Efficiency Adsorption of Hexavalent Chromium in Potable Water: Adsorption Performance and Mechanism Insight

Particularly, because of the leakage risk of metal elements from sludge carbon, little attention has been focused on using sludge activated carbon as an adsorbent for the removal of Cr (VI) from contaminated water sources. Herein, a novel sludge carbon derived from dewatered cassava sludge was synthesized by pyrolysis using ZnCl2 as an activator at the optimal conditions. The prepared sludge activated carbon possessed a large BET surface (509.03 m2/g), demonstrating an efficient removal for Cr (VI). Although the time to reach equilibrium was extended by increasing the initial Cr (VI) concentration, the adsorption process was completed within 3 h. The kinetics of adsorption agreed with the Elovich model. The whole adsorption rate was controlled by both film and intra-particle diffusion. The Cr (VI) removal efficiency increased with elevating temperature, and the adsorption equilibrium process followed the Freundlich isotherm model. The adsorption occurred spontaneously with endothermic nature. The removal mechanism of Cr (VI) on the prepared sludge activated carbon depended highly on solution pH, involving pore filling, electrostatic attraction, reduction, and ion exchange. The trace leakage of metal elements after use was confirmed. Therefore, the prepared sludge activated carbon was considered to be a highly potential adsorbent for Cr (VI) removal from contaminated raw water.