Agricultural Research Service, San Joaquin Valley Agricultural Sciences Center, United States Department of Agriculture, 9611 South Riverbend Avenue, Parlier, California 93648-9757, United States.
J Agric Food Chem. 2015 Apr 1;63(12):3094-103. doi: 10.1021/jf505193e. Epub 2015 Mar 23.
End-products of tree nuts and tree fruits grown in California, USA were evaluated for the ability to remove methyl bromide (MB) from ventilation effluent following postharvest chamber fumigation. Activated carbon sorbents from walnut and almond shells as well as peach and prune pits were prepared using different methods of pyrolysis, activation, and quenching. Each source and preparation was evaluated for yield from starting material (%, m/m) and performance on tests where MB-containing airstreams were directed through a columnar bed of the activated carbon in an experimental apparatus, termed a parallel adsorbent column tester, which was constructed as a scaled-down model of a chamber ventilation system. We report the number of doses needed to first observe the breakthrough of MB downstream of the bed and the capacity of the activated carbon for MB (%, m/m) based on a fractional percentage of MB mass sorbed at breakthrough relative to mass of the bed prior to testing. Results were based on a novel application of solid-phase microextraction with time-weighted averaging sampling of MB concentration in airstreams, which was quantitative across the range of fumigation-relevant conditions and statistically unaffected by relative humidity. Activated carbons from prune pits, prepared either by steam activation or carbon dioxide activation coupled to water quenching, received the greatest number of doses prior to breakthrough and had the highest capacity, approximately 12-14%, outperforming a commercially marketed activated carbon derived from coconut shells. Experimental evidence is presented that links discrepancy in performance to the relative potential for activated carbons to preferentially sorb water vapor relative to MB.
美国加利福尼亚州种植的坚果和水果的终产物被评估是否具有从采后腔室熏蒸后的通风废气中去除甲基溴 (MB) 的能力。核桃和杏仁壳以及桃核和李核的活性炭吸附剂是通过不同的热解、活化和淬火方法制备的。每种来源和制备方法都根据从起始材料中获得的产率（%，m/m）和在测试中的性能进行了评估，在测试中，含有 MB 的空气流被引导通过实验设备中活性炭的柱状床，该设备被称为平行吸附柱测试仪，它是一个 chamber 通风系统的缩小模型。我们报告了首先观察到床下游 MB 突破所需的剂量数，以及基于在测试之前相对于床质量吸附的 MB 质量的分数百分比，活性炭对 MB 的容量（%，m/m）。结果基于空气流中 MB 浓度的固相微萃取与时间加权平均采样的新颖应用，该应用在与熏蒸相关的条件范围内是定量的，并且不受相对湿度的影响。通过蒸汽活化或二氧化碳活化与水淬火相结合制备的李核活性炭，在突破之前接受了最多的剂量，并且具有最高的容量，约为 12-14%，优于从椰子壳中提取的商业销售的活性炭。实验证据表明，性能差异与活性炭优先吸附水蒸气而不是 MB 的相对潜力有关。
