【时文选读】The Carbon Vault 碳库：二氧化碳的矿化

【时文选读】The Carbon Vault 碳库：二氧化碳的矿化Part.One

The notion of storing CO2in minerals isn’t new. Plans to capture the gas from the air or power plant exhaust often call for injecting it into underground rock formations that, like mine waste, react to form carbonates. And certain rocks naturally capture CO2in a process known as weathering. Vast ridges of a mineral called peridotite mineralize CO2fromthe air, forming white veins resembling marbling in steak. Mine wastes behave the same way.

将二氧化碳矿化封存的概念并不稀奇。人为手段通常的思路是：捕集大气中弥漫的二氧化碳或电厂排放的废气，将之注入可发生化学反应的地下岩层，这些岩层和矿山废料一样，会与二氧化碳反应形成碳酸盐矿物。同时，某些岩石能自然吸收二氧化碳，这一过程被称为“风化”。比如，橄榄岩能将空气中的二氧化碳矿化成白色矿脉，覆在其巨大山脊上形如牛排上的雪花纹。矿山废料对二氧化碳的固化方式亦是如此。

Part.Two

Still, weathering is slow, and most alkaline wastes wind up either buried or submerged in ponds, and thus aren’t exposed to air. At Gahcho Kué, Dipple and his students tested a way to speed up the process. The waste soaked up CO2for as long as 44 hours, they found, converting it into minerals. The newly made magnesium carbonate minerals acted like glue, solidifying the previously free-flowing tailings, much like sand turned to sandstone. Most important, the waste took up CO2200 times faster than it did through natural weathering, Dipple says.

不过，自然的风化过程是缓慢的，而且大多数碱性废料都淹埋在了池塘里，因而无法接触空气并吸收二氧化碳。在加拿大的Gahcho Kué钻石矿场里，Dipple和他的学生们尝试加速风化这一过程。经过实验他们发现，在仅长44个小时的吸收和矿化后，废料将二氧化碳转变成了矿物质。新形成的碳酸镁矿物如同胶水，将原先随处散落的尾矿颗粒固着，很像沙子形成砂岩的过程。Dipple说，利用废料吸收二氧化碳的速度比自然风化快200倍，这一点非常重要。

Part.Three

CO2mineralization could help remediate environmental problems that mining creates, such as the release of heavy metals from pulverized rock. Earlier this year in Economic Geology, Wilson and her colleagues reported that techniques that accelerate weathering, such as adding acid, effectively trap heavy metals inside newly formed carbonate minerals, keeping them out of groundwater. Other teams have shown that the carbonates can also trap hazardous residual asbestos fibers in chrysotile mine tailings. “You can lock away just about anything,” Wilson says.

二氧化碳的矿化还可以缓解矿采中的环境问题，比如解决粉碎岩石时释放的重金属。在年初出版的《经济地质学》中，Wilson与同事报告了加速风化的一些技术，如通过添加酸能有效将重金属封存在新形成的碳酸盐矿物中，从而使其远离地下水。也有一些研究小组发现，碳酸盐矿物能封存温石棉尾矿中残留的有害石棉纤维。Wilson 认为，“利用二氧化碳的矿化能储存几乎任何有害物质。”

Part.Four

Other industrial wastes, such as red mud from aluminum production and “slags” leftover from making steel and iron, also harbor plenty of chemical reactivity to bind and store CO2. However, according to the National Academy of Sciences (NAS), fully carbonating these wastes could require building costly plants to speed the reactions.

其它的工业废料，诸如生产铝的过程中出现的赤泥，锻钢和炼铁后残余的矿渣，都能与二氧化碳发生大量的化学反应并结合成矿物质将之封存。不过，根据美国国家科学院（NAS）的说法，将这些工业废料完全碳酸盐化则需要耗巨资建厂来加速反应过程。

Part.Five

In another environmental plus, the NAS panel said, carbonated wastes of all kinds could serve as raw material for concrete and road aggregate. The report noted that replacing 10% of building materials with carbonated minerals could reduce CO2emissions by 1.6 GTs per year by lowering emissions from cement production. Numerous companies around the globe have already jumped into the field to make and sell the new materials.

该学院专家组还提到二氧化碳矿化的另一环境优势，碳酸盐化的各种工业废料可作为原材料用于制作混凝土和修路用骨料。报告指出，用碳酸盐矿物替代10%的水泥