No abstract

The application of almond shell as a low cost natural adsorbent to remove Hg(2+) from aqueous solution was investigated. Batch experiments were carried out to evaluate the adsorption capacity of the material. The chemical and physical parameters such as pH, sorbent amount, initial ion concentration, and contact time were optimized for the maximum uptake of mercury onto the solid surface. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models, and the experimental data were found to fit the Langmuir model rather than the Freundlich. The maximum adsorption capacity obtained from the Langmuir isotherm was 135.13 mg/g. A kinetic study was carried out with pseudo-first-order and pseudo-second-order reaction equations and it was found that the Hg(2+) uptake process followed the pseudo-second-order rate expression. The thermodynamic values, ΔG(0), ΔH(0) and ΔS(0), indicated that adsorption was an endothermic and spontaneous process. The potential of this material for mercury elimination was demonstrated by efficient Hg(2+) removal from a synthetic effluent.

AbstractBackground: Machines, especially pressing machines, have a huge contribution to the incidence of occupational accidents and their costs. Objective: The purpose of this descriptive-analytical study was to evaluate the risk of pressing operations. For this purpose, two traditional and new methods of risk assessment were used. Methods: This study was carried out in a press workshop of one of the automobile production factories in 2017. Risk assessment was performed in two ways: Failure modes (FM) and effects analyzes (EA) and functional resonance analysis method (FRAM) based on extended resilience engineering. After identifying the six aspects of the operation of pressing, their variability and exacerbation were determined. Findings: From 72 potential breakdowns, twenty mode in one of the risk factors of the risk priority number (severity, probability and detection rates) were equal or greater than five, and other failure modes identified were normal and not require new corrective actions. Fifteen functions were also identified for press operations, which seven operations including planning, mapping, raw material supply, forklift lifting, stamping, census, and delivery of preformed parts were resonating. Conclusion: Considering the focus of the method of FM and EA on technical issues and the visibility of this method, as well as the overall and organizational view, the FRAM, the simultaneous use of these two methods, significantly contributes to improving the safety of the system makes.

Rice husk (RH) is a very effective natural adsorbent for fast removal of heavy metal cations from water solutions. Application of RH for removal of some heavy metal ions, such as Ni, Zn, Mn, Co, Cu, Pb and Cd from water solutions has been studied and different maximum adsorption capacities and a variety of optimized conditions were reported in the literature. In this work, the efficiency of RH harvested from different climatic regions was studied. For this proposal, different RH samples were collected from three different climatic regions of Iran (nominated as RH1 to RH3); their removal efficiencies of heavy metal cations of Ni(2+), Cu(2+) and Cd(2+) were investigated and compared. The adsorption data at optimum conditions could be assessed well by both Langmuir and Freundlich models. Statistical analysis of the results of adsorption isotherms showed that different RH samples have different efficiencies in uptake of these heavy metal ions. The RH samples were characterized using Fourier transform infrared spectroscopy and Boehm titration, which indicated that amounts of functional groups differed between RHs that are grown in different climatic conditions.

Ambient air contaminants have different adverse effects on human health, environment, and structures. Some pollutions are more toxic and have unfavorable effects on workers' and public health, for example, cyanide/isocyanide vapor produced in some processes or in burning of polyurethane compounds, which is a toxic gas that can kill or cause harms impossible to reverse. It is so necessary that air pollutants will be controlled and treatment will be provided for the workers and public who are exposed or exhausted to the environment. Industrial ventilation (general ventilation, dilution ventilation, and local exhaust ventilation) is an appropriate system to control indoor air pollutions. Local exhaust ventilation (LEV) has different segments such as hoods, fittings, collectors (air cleaners), stacks, and fans that could collect and treat indoor and outdoor air contaminants. Each well-designed segment of a local exhaust ventilation is a vital subject that can cause an appropriate or inappropriate performance of systems. A well-designed LEV can lead to obtain a high efficiency level of pollution removal and minimum exposure (workers, public, and environment) to pollutants and save costs and energy.