Aliyar Mousavi

A sustainable sulfate process to produce TiO2 pigments

Titanium dioxide (TiO2) is a widely used white pigment. TiO2 production in 2006 was about 1,400,000 metric tons in the USA. The two major processes to manufacture TiO2 are the chloride process and the sulfate process. Currently, the TiO2 industry finds the waste generated in the chloride process less than the waste generated in the sulfate process in its present design, despite generating large quantities of process-related carbon dioxide and carbon monoxide. As a consequence, the sulfate process appears less economical, notably due to the production of green vitriol, FeSO4·7H2O, as a major waste. Here, we describe a more sustainable sulfate process based on an earlier study on thermal decomposition of iron(II) sulfates. In the sustainable sulfate process, FeSO4·7H2O waste is used for greener production of sulfuric acid, H2SO4, used in turn for the digestion of ilmenite. Theoretical and actual yields of waste byproducts per metric ton of TiO2 produced are used to show the environmental and economic advantages of the sustainable sulfate process.

The chlor-alkali process: A review of history and pollution

ABSTRACT The chlor-alkali process is a widely used electrolytic process that yields chlorine and caustic soda. It has been in use since the 19th century and is a primary industry in the United States, Western Europe, and Japan. There are three primary electrolytic processes for producing chlorine and caustic soda: the diaphragm cell process, the mercury cell process, and the membrane cell process. The first two have been used for over 100 years; the latter was developed in the past 60. The two oldest methods are used the most throughout the world and have been proven to be the most environmentally unfriendly through their use of asbestos and mercury, respectively. The membrane cell process is a superior method in its energy efficiency and lack of harmful chemicals. This article reviews the history of each method, addresses changes in its modern technology and use, and discusses the emissions and outputs of the processes.

Mercury speciation and safety evaluation of cinnabar-containing traditional medicines: a mini-review

The use of cinnabar, which is mainly composed of mercury(II) sulfide (HgS), in traditional Chinese medicines and Indian Ayurvedic medicines has two thousand years of history. However, because of the excessively high mercury content in cinnabar-containing traditional medicines, they are forbidden in the US and European markets. Commenting on a study in which chronic nephrotoxicity of cinnabar has been studied and compared with that of a common mercurial, this mini-review covers an introductory toxicological chemistry of cinnabar in the human body. It confirms that the speciation of mercury in cinnabar in the human body should be taken into consideration in the “toxicity” evaluation of cinnabar-containing traditional medicines. Further, in light of modern science, it categorically analyzes the uses of cinnabar in traditional medicines, in order to address if the level of its therapeutic effectiveness is desirable enough to have cinnabar-containing traditional medicines undergo “safety” evaluation as todays over-the-counter/prescription medicines do.

Lead Sources, Toxicity, and Human Risk in Children of Developing Countries: A Mini–Review

Lead (Pb) is one of the oldest metals known to man and has been useful since the ancient era. However, it is known today that Pb is severely toxic to humans. Briefly reviewing the sources (both natural and anthropogenic) of Pb in the environment, this mini-review discusses how Pb continues to put the health of humans, especially children in developing countries, at risk. The toxicological processes through which Pb acts as a poison in the human body, primarily affecting the nervous system, are reviewed briefly and followed by a discussion on how the public is exposed to Pb and several case studies on Pb poisoning in children from developing countries. The case studies are on children from different regions of the developing world, and they show how highly children from developing countries are at risk of Pb poisoning. Further, the reviewed cases may be relevant to litigation as environmental toxic torts. Therefore, public awareness and introducing environmental preventive regulations concerning exposure to Pb need to continue globally.

Mercury (Hg) Levels in the Caspian Sea Kilka Fish: A Communication

The Caspian Sea is a unique aquatic ecosystem, as it is the largest lake in the world. Unfortunately, human activities, such as the offshore oil production and chlor-alkali industry, are continuously contaminating the Caspian Sea. The environmental health issue of mercury (Hg) poisoning caused by Hg-contaminated fish has concerned some experts about the safety of fish consumption by the human populations of the Caspian Sea region. In the present study, the Hg levels in three Iran-produced canned common kilka samples of identical commercial composition were determined. The Hg levels in the studied fish samples were found to be in the range 0.00655 ± 0.00007 mg/kg. The results were compared to a number of regulatory limits. According to the results, the fish individuals included in the very limited set of randomly selected Caspian Sea kilka fish in this study are low in Hg, and, from the perspective of Hg contamination, they should be fit for human consumption. It is not known how representative this limited sampling is for all the Caspian Sea kilka fish population, and more studies are needed in this respect.

A forensic hypothesis for the mystery of al-Hasan’s death in the 7th century: Mercury(I) chloride intoxication

The puzzle of a mysterious death in the Middle Ages has been hypothesized in terms of contemporary forensic legal and scientific methods. That al-Hasan ibn-‘Ali died in 669 aged just 45 has been forensically analyzed based on written sources that dictate eyewitness accounts of historical events. The report of the contemporaneous poisoning of another individual who resided under the same household as al-Hasan’s and experienced similar, yet non-lethal, symptoms has served as the beginning of the analysis. In light of ancient (medieval) documents and through using mineralogical, medical, and chemical facts, it has been hypothesized that mineral calomel (mercury(I) chloride, Hg2Cl2) from a certain region in the Byzantine Empire (present-day western Turkey) was the substance primarily responsible for the murder of al-Hasan.

Gold Mining: Is It Worth Its Weight?

Gold (Au) accounts for only 0.004 g/ton of the earths crust and is the most desired element. With an average annual world production of approximately 2,500 tons, the current methods of Au mining in developing countries cause major environmental issues. These issues vary from deforestation to cyanide and mercury (Hg) contamination. This article presents several cases of environmental catastrophes caused by Au mining in different regions of the world (Africa, the Middle East, Eastern Europe, and South America). It discusses the currently available processes for the large-scale extraction of metallic Au grains and supports the need for an alternative sustainable process.

Revival of the oxidation number method for balancing redox equations

A study published in 2009 involving first-year students at Tshwane University of Technology in Pretoria, Republic of South Africa, showed that most of the students at that institution were not able to balance chemical equations satisfactorily. For balancing relatively complex redox equations, the oxidation number method is found to be the simplest method. However, it appears to the author that the number of professors who teach this method is strictly decreasing, which will ultimately cause the method to be extinct. One reason for its apparent gradual disappearance might be that many students have not learned the oxidation number method well. In this article, with the aim of reviving the method, redox equations are classified into three classes referred to and discussed as Class I, Class II and Class III, based on how exactly the method is applicable to balance the equations. In light of the solid theoretical foundation and the systematic educational classification presented, this article will hopefully serve as an encouragement to chemical educators to teach the method, so that its use can continue.

Determination of thiosulfate concentrations by gravimetric analysis: A desirable experiment for chemical education

ABSTRACT An electrochemistry-based gravimetric method of analysis for the determination of thiosulfate concentrations in aqueous solutions and its application in chemical education are introduced. Nine standard aqueous thiosulfate solutions with triplicate concentrations of 0.02 M, 0.03 M, and 0.04 M were prepared in 1.0 M hydrochloric acid. The elemental sulfur produced in each sample was recovered by filtration, and the mass of the recovered elemental sulfur and the electrochemically determined equilibrium constant of the reaction at 25°C (Keq = 3.5) were used to determine the concentration of thiosulfate in each standard solution. The method % Error is 4.9 ± 3.0, which means that the average method % Error is less than 5.0. GRAPHICAL ABSTRACT

Mercury Salts in Chinese Traditional Medicines: A Human Health Concern in an Inorganic Chemistry Perspective

The news of Chinese traditional medicines reaching Iran suggests that these medicines are becoming increasingly available internationally. Despite the long history of the toxic effects of mercury, mercury compounds are commonly used in Chinese traditional medicines. Two mercurials contained in some Chinese traditional medicines are the salts mercury(II) sulfide (HgS) and mercury(I) chloride (Hg2Cl2). Toxicological evidence from the past and principles of reactivity in inorganic chemistry are used to address the human health concern that is caused by Chinese traditional medicines in which either of the two mercury salts is present. The chemistry discussed in this article shows that the ingestion of HgS or Hg2Cl2 causes the introduction of aqueous mercury cations, especially Hg2+, into the human body. With that chemistry discussed and with the addressed toxic effects, science at the present time finds the Chinese traditional medicines that contain HgS or Hg2Cl2 disadvantageous compared to the antibiotics and sedatives that are available in modern medicine today.