Steve L. Hoeffner

Bio: Steve L. Hoeffner is an academic researcher from Clemson University. The author has contributed to research in topics: Environmental remediation & Soil contamination. The author has an hindex of 3, co-authored 6 publications receiving 290 citations.

A Critical Review of Stabilization/Solidification Technology

Abstract: The processes and techniques of stabilization/solidification (S/S) have matured into an accepted, and important, part of environmental technology. As a result, a great many S/S methods have been promoted recently and offered for the treatment of hazardous and other wastes from industry, municipalities, and government sources. The purpose of this article is review these methods critically in light of the current regulatory atmosphere that controls and often mandates their use. An overview of the technology is provided. The generic and proprietary S/S processes (chemical processes, physical processes, and thermal processes) are described. Of these, six generic chemical processes dominate the field and encompass nearly all of the treatment work and proprietary products to date: Portland cement, cement/fly ash, cement/soluble silicate, lime/flyash, kiln dust, and phosphate. Current and anticipated major waste streams using S/S technology today are summarized. The S/S approach for each of these are reviewed. F...

The History of Stabilization/Solidification Technology

Abstract: The processes and techniques of S/S matured into an accepted, and important, part of environmental technology How this came about is both interesting and instructive for those working this discipline as well as others fascinated by a technical area that is still part art and part science With few exceptions, the history of S/S for use on hazardous waste residues dates only from about 1970, when the EPA was established Most of the impetus for S/S of hazardous wastes was provided when the Resource Conservation and Recovery Act was passed in 1976, although real implementation did not occur until after 1980 with the promulgation of regulations for a Federal hazardous waste management system under Subtitle C of RCRA With the passage of the HSWA in 1984 and the subsequent LDR regulations beginning in 1985, and CERCLA and SARA and their regulations, most of the present regulatory system came into being The most recent, and far reaching, ramifications of regulation with respect to S/S are due to the Land Dis

Variable hardness orthotic

Abstract: Orthotics and methods for forming orthotics are described. The orthotics can be designed with a patient-specific design and can include variation in hardness across the orthotic so as to satisfy clinical need. An orthotic can be a custom-designed orthotic formed according to an additive manufacturing process such as a 3-D printing methodology. Through utilization of on-site formation methods such as 3-D printing, an orthotic can be designed, formed and fit at the point of care in a much shorter time period than traditional orthotics. The orthotics can include a layer that includes a plurality of cells across the layer. The layer can exhibit variable hardness across the layer through variation in cell void volume and optionally material of formation across the layer.

Characterization of plutonium contaminated soils from the nevada test site in support of evaluation of remediation technologies

Abstract: The removal of plutonium from Nevada Test Site (NTS) area soils has previously been attempted using various combinations of attrition scrubbing, size classification, gravity based separation, flotation, air flotation, segmented gate, bioremediation, magnetic separation and vitrification. Results were less than encouraging, but the processes were not fully optimized. To support additional vendor treatability studies soil from the Clean Slate II site (located on the Tonopah Test Range, north of the NTS) were characterized and tested. These particular soils from the NTS are contaminated primarily with plutonium-239/240 and Am-241. Soils were characterized for Pu-239/240, Am-241 and gross alpha. In addition, wet sieving and the subsequent characterization were performed on soils before and after attrition scrubbing to determine the particle size distribution and the distribution of Pu- 239/240 and gross alpha as a function of particle size. Sequential extraction was performed on untreated soil to provide information about how tightly bound the plutonium was to the soil. Magnetic separation was performed to determine if this could be useful as part of a treatment approach. The results indicate that about a 40% volume reduction of contaminated soil should be achievable by removing the >300 um size fraction of the soil. Attrition scrubbing does not effect particle size distribution, but does result in a slight shift of plutonium distribution to the fines. As such, attrition scrubbing may be able to slightly increase the ability to separate plutonium-contaminated particles from clean soil. This could add another 5-10% to the mass of the clean soil, bringing the total clean soil to 45-50%. Additional testing would be needed to determine the value of using attrition scrubbing as well as screening the soil through a sieve size slightly smaller than 300 um. Since only attrition scrubbing and wet sieving would be needed to attain this, it would be good to conduct this investigation. Magnetic separation did not work well. The sequential extraction studies indicated that a significant amount of plutonium was soluble in the ''organic'' and ''resistant'' extracts. As such chemical extraction based on these or similar extractants should also be considered as a possible treatment approach.