Recycling cadmium

Henkel Rearrangement of Benzoic Acid and Phthalic Anhydride. Henkel technology is based on the conversion of benzenecarboxyhc acids to their potassium salts. The salts are rearranged in the presence of carbon dioxide and a catalyst such as cadmium or zinc oxide to form dipotassium terephthalate, which is converted to terephthahc acid (59—61). Henkel technology is obsolete and is no longer practiced, but it was once commercialized by Teijin Hercules Chemical Co. and Kawasaki Kasei Chemicals Ltd. Both processes foUowed a route starting with oxidation of napthalene to phthahc anhydride. In the Teijin process, the phthaHc anhydride was converted sequentially to monopotassium and then dipotassium o-phthalate by aqueous recycle of monopotassium and dipotassium terephthalate (62). The dipotassium o-phthalate was recovered and isomerized in carbon dioxide at a pressure of 1000—5000 kPa ( 10 50 atm) and at 350—450°C. The product dipotassium terephthalate was dissolved in water and recycled as noted above. Production of monopotassium o-phthalate released terephthahc acid, which was filtered, dried, and stored (63,64). 

Nickel-cadmium batteries are rechargeable because the nickel and cadmium hydroxides products adhere tightly to the electrodes. More than 1.5 billion Ni-Cd batteries are produced every year. These batteries are not without drawbacks, however. Cadmium is a toxic heavy metal that adds weight to the battery. Moreover, even rechargeable batteries degrade eventually and must be recycled or disposed of in a benign way. 

Dutch law has indicated NAA as the technique of choice for the analysis of polymer waste (recycling). INAA has been recommended as the analysis technique for the determination of cadmium in industrial products. 

The pollutants of concern are the same as in wet basic oxygen furnaces, but the concentration of metals (primarily lead and zinc, but also arsenic, cadmium, copper, chromium, and selenium) in wastewater is higher because of the higher percentage of scrap charged. Wastewater treatment operations are similar to those for the wet basic oxygen furnaces, including sedimentation in clarifiers or thickeners and recycle of the water.14... 

As mentioned above, approximately 7% of the total sulfur present in lead ore is emitted as S02. The remainder is captured by the blast furnace slag. The blast furnace slag is composed primarily of iron and silicon oxides, as well as aluminum and calcium oxides. Other metals may also be present in smaller amounts, including antimony, arsenic, beryllium, cadmium, chromium, cobalt, copper, lead, manganese, mercury, molybdenum, silver, and zinc. This blast furnace slag is either recycled back into the process or disposed of in piles on site. About 50 to 60% of the recovery furnace output is slag and residual lead, which are both returned to the blast furnace. The remainder of this dross furnace output is sold to copper smelters for recovery of the copper and other precious metals. 

Shredded circuit boards. Circuit boards are metal boards that hold computer chips, thermostats, batteries, and other electronic components. Circuit boards can be found in computers, televisions, radios, and other electronic equipment. When this equipment is thrown away, these boards can be removed and recycled. Whole circuit boards meet the definition of scrap metal, and are therefore exempt from hazardous waste regulation when recycled. On the other hand, some recycling processes involve shredding the board. Such shredded boards do not meet the exclusion for recycled scrap metal. In order to facilitate the recycling of such materials, U.S. EPA excluded recycled shredded circuit boards from the definition of solid waste, provided that they are stored in containers sufficient to prevent release to the environment, and are free of potentially dangerous components, such as mercury switches, mercury relays, nickel-cadmium batteries, and lithium batteries. 

Nickel-cadmium rechargeable batteries are being researched. Alternatives such as cadmium-free nickel and nickel hydride systems are also being researched, but nickel-cadmium batteries are unlikely to be totally replaced. Nickel-cadmium batteries can be reprocessed to reclaim the nickel. However, currently, approximately 80% of all nickel-cadmium batteries are permanently sealed in appliances. Changing regulations may result in easier access to these nickel-cadmium batteries for recycling. 

To reduce the amount of waste, start with pollution prevention. Starting with pollution prevention leads to less or no leftover waste that could potentially become hazardous wastes. The use of rechargeable batteries results in a longer life span and use fewer batteries. However, rechargeable batteries still do contain heavy metals such as nickel-cadmium. When disposing of rechargeable batteries, recycle them if possible. 

In the early 1980s, the world witnessed the sale of the first personal computers. Its transition from the relatively bulky and slow first units to the sleek, speed demons has made the computer truly revolutionary. With each improvement in computers, however, comes the increasing problem of what to do with the ever increasing number of computer e-wastes. The U.S. EPA estimates that nearly 250 million computers will become obsolete in the next five years in the United States alone. Unfortunately, only approximately 10% of these old computers that are retired each year are being recycled. This presents a substantial concern because toxic elements such as lead, cadmium, mercury, barium, chromium, beryllium as well as flame retardant, and phosphor are contained in a typical computer and there would be potential harm if there was a release of these elements into the environment.1... 

Fishbein, B., Extended Product Responsibility A New Principle for Product-Oriented Pollution Prevention, Industry Program to Collect and Recycle Nickel-Cadmium (Ni-Cd) Batteries, U.S. Environmental Protection Agency, EPA530-R-97-009, Washington, DC, pp. 6-1-6-32, 1997. 

In addition, the concern about e-waste not only focuses on its vast quantity generated daily, but also more on the need to handle the toxic chemicals embedded in it. It is well known that e-waste contains lead, beryllium, mercury, cadmium (Cd), and brominated flame retardants (BFRs) among other chemical materials [3]. Furthermore, highly toxic chemicals such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polybrominated dibenzo-p-dioxins and dibenzo-furans (PBDD/Fs) can be formed during the recycling process [4]. 

Municipal solid waste (MSW), 25 864 as biomass, 3 684 cadmium in, 4 489-490 characteristics of leachates in, 25 867t characterizing, 25 866-869 collection of, 25 869-870 composition analysis for, 27 365t ferrous scrap in, 27 411 incineration of, 25 872-873 mixed, 27 367-369 preparation of, 27 367-369 processing, 27 364-371 quantity and composition of, 27 362-364 recovery rates for, 27 364, 366-367t recycled, 27 360, 362-371 toxic chemicals in, 25 875-876 Municipal waste sludge, as biomass, 3 684 Municipal water, for aquaculture, 3 198 Municipal water softening methods,... 

Like many technological innovations, nickel-cadmium batteries carry risks as well as benefits. After being discharged repeatedly, they eventually wear out. In theory, worn-out nicad batteries should be recycled. In practice, however, many end up in garbage dumps. Over time, discarded nicad batteries release toxic cadmium. The toxicity of this substance makes it hazardous to the environment, as cadmium can enter the food chain. Long-term exposure to low levels of cadmium can have serious medical effects on humans, such as high blood pressure and heart disease. 

In 1990, 10,600 tons of soil contaminated with cadmium and lead from a former battery recycling facility in Savannah, Illinois, were treated with the STC Remediation, Inc., reagents. The vendor states that the reagents, on-site technical support personnel, and the on-site quality assurance personnel cost 51.00 per ton of soil treated (D113382, p. 13). 

The data also indicate that Octolig can have a long "recycling life" because the heavy metal ions were removed, not comparahvely irmocuous ones like calcium that affect TDS (Total Dissolved Salts). The contrast between removal of cadmium or chromium versus non-removal of calcium ion shows the advantage of being able to design supported chelators for specific purposes. Supported iminodiacetic acid, for example would have removed cadmium, but also calcium ions as well, reducing in this instance the useful capacity of this material.. 

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