Secondary Aluminum Processing Waste: Salt Cake Characterization and Reactivity

Thirty-nine salt cake samples were collected from 10 SAP facilities across the U.S. The facilities were identified by the Aluminum Association to cover a wide range of processes. Results suggest that while the percent metal leached from salt cake was relatively low, the leachable metal content may still pose a contamination concern and potential human and ecological exposure if uncontrollably released to the environment. As a result, salt cake should always be managed at facilities that utilize synthetic liner systems with leachate collection (the salt content of the leachate will increase the hydraulic conductivity of clay liners within few years of installation). The mineral phase analysis showed that various species of aluminum are present in the salt cake samples with a large degree of variability. The relative abundance of various aluminum species was evaluated but it is noted that the method used is a semi-quantitative method and as a result there is a limitation for the data use. The analysis only showed a few aluminum species present in salt cake which does not exclude the presence of other crystalline species especially in light of the variability observed in the samples.Results presented in this document are of particular importance when trying to understand concerns associated with the disposal of salt cake in MSW landfills. From and end-of-life management perspective, data presented here suggest that salt cake should not be size reduced before disposal. Also, care should be taken not to size reduce it after disposal by compacting it with heavy bulldozers. The MSW decomposition process is an exothermic and as a result MSW landfill temperatures are typically greater than 37 °C and may reach 50 °C or greater. The elevated temperatures present in most MSW landfills can be conducive and could initiate salt cake reactions that otherwise may not take place. Furthermore, elevated temperatures can increase the rate of the salt cake reaction which further propagate the salt cake reaction. Even outside of MSW landfills, once a salt cake reaction starts, it may self-propagate and increase the rate at which the reaction occurs. While the heat generation potential per gram of salt cake sample is a sample specific parameter, the results presented herein suggest that higher environmental temperatures tend to intensify the salt cake reaction. At elevated temperatures encountered in MSW landfills, elevated levels of H2 gas may be generated as a result of salt cake reactivity and will be of concern. Hydrogen is an explosive gas and can potentially cause fires. Hydrogen is even of greater concern if generated in MSW landfills. Apart from being a fire hazard when mixed with CH4, landfill gas collection systems are not designed to handle H2 since MSW landfill gas generally consists of CH4 and CO2 at ~ 50/50 ratio. Like hydrogen, methane is an explosive gas and care must be taken if salt cake reacts with liquids. But unlike hydrogen, in an MSW

Art Talk with Debra Cartwright

At one point or another, most little girls dream of becoming a princess when she grows up. But what if the princesses in books and movies don’t have hair like you do? What if the models you admire as a self-conscious adolescent don’t have the faces or bodies you see when you look in the mirror…

Gravitational waves detected 100 years after Einstein’s prediction

aerial view of LIGO detector

For the first time, scientists have observed ripples in the fabric of spacetime called gravitational waves, arriving at Earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein’s 1915 general theory of relativity and opens an unprecedented new window to the cosmos.

Gravitational waves carry information about their dramatic origins and about the nature of gravity that cannot be obtained from elsewhere. Physicists have concluded that

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This is an NSF News item.

Notice of Multistakeholder Process to Develop Best Practices for Privacy, Transparency, and Accountability Regarding Commercial and Private Use of Unmanned Aircraft Systems Meeting

February 11, 2016

NTIA will convene a meeting of a multistakeholder process concerning privacy, transparency, and accountability issues regarding commercial and private use of unmanned aircraft systems on February 24, 2016. The meeting will be held from 1 p.m. to 5 p.m., Eastern Time in the Boardroom at the American Institute of Architects, 1735 New York Avenue NW., Washington, DC 20006.

GMC ( 16V069000 )

Dated: FEB 03, 2016 General Motors LLC (GM) is recalling certain model year 2015-2016 Chevrolet Silverado 2500 and 3500 heavy duty trucks manufactured October 1, 2013, to February 1, 2016, 2015-2016 Chevrolet Tahoe Polic…

CHEVROLET ( 16V069000 )

Dated: FEB 03, 2016 General Motors LLC (GM) is recalling certain model year 2015-2016 Chevrolet Silverado 2500 and 3500 heavy duty trucks manufactured October 1, 2013, to February 1, 2016, 2015-2016 Chevrolet Tahoe Polic…

EVERGREEN ( 16V032000 )

Dated: JAN 21, 2016 Evergreen Recreational Vehicles, LLC (Evergreen) is recalling certain model year 2013-2015 Amped and Amped Reactor recreational vehicles manufactured June 1, 2013, to August 31, 2015. In the affected…