|Klasson, K Thomas|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/29/2012
Publication Date: N/A
Technical Abstract: Dibromochloropropane (1,2-dibromo-3-chloropropane or DBCP) is regulated by the U.S. Environmental Protection Agency under the National Primary Drinking Water Regulations to a maximum of 0.2 µg/L (0.2 ppb) in drinking water. DBCP was primarily used as an unclassified nematicide for vegetables and perennial crops and is no longer produced in the U.S. Its use contaminated some groundwater and aquifers of nearby agricultural communities. Here, we describe the performance of activated biochars made via pyrolysis and steam activation of almond shells, available locally in proximity to contaminated areas, in removing DBCP. The specific surface area (BET) was approximately 360 m2/g of activated biochar and the majority of pore diameters were less than 2 nm, indicating that most of the pores were micro-pores. The yield of activated biochar from the raw material was 23% (dry basis) and fixed carbon content (from proximate analysis) increased from 21% (dry-basis) in the almond shells to 66% in the activated biochar. The ash content of the activated biochar was 19%. Using a 5000 ppm DBCP standard, the well water (and in some cases deionized water) was spiked to a variety of concentrations. Results showed that regardless of the background composition (deionized water or well water) the loading capacities were the same and appeared to follow a typical isotherm pattern. Based on these results, we concluded that steam-activated biochar made from almond shells could be used as a DBCP adsorbent from well water intended for consumption. Assuming that the well water typically contains 0.25 ppb DBCP, it can be estimated from the isotherm that activated biochar can reach a loading capacity of 19 µg DBCP/g of biochar, which means that approximately 80 L can be treated by 1 g of almond shell-based steam-activated biochar. The laboratory results were confirmed in on-site column studies where the activated biochars removed 100% of the contaminants.