Activated carbon is commonly used in the drinking water industry for the removal of a variety of contaminants including, for example: chlorinated, halogenated organic compounds (such as trihalomethanes), adsorbable organic halogens (AOX), odorous materials, colored contaminants, compounds for biological treatment systems, aromatics, pesticides, and the like. This purification is simply accomplished through direct contact of the contaminated water with the activated carbon. Almost all commercially available activated carbon contains ppm levels of arsenic and antimony, originating from the natural composition of raw materials from which said activated carbon is produced. When directly contacted with the water, activated carbon may leach small fractions of said arsenic and antimony in the form of soluble oxy-anions, at ppm levels. Albeit miniscule, leaching is nevertheless undesirable, but is known to be reduced by subjecting said activated carbon to acid washing in a separate procedure prior to utilizing the activated carbon for water purification. Acid washing strips away the majority of the leachable fractions of said arsenic and antimony.
Acid washing procedures may contain several steps, typically including neutralization with a mild base solution followed by final water rinsing to remove resulting salts from said activated carbon. Typically, the amount of neutralizing agent, such as sodium carbonate, is controlled to provide a neutral or slightly basic pH of said final rinse water. The neutral or slightly basic pH of said final rinse water provides a contact pH of final acid washed product, after drying, that approaches a contact pH of 9 to 11. Embodiments described herein are useful for providing reduction in leachable arsenic and antimony in activated carbon for filtration, said reduction exceeding that achieved by typical acid washing.