Phosphate recovery using amorphous calcium silicate hydrates

Abstract

Amorphous calcium silicate hydrates (A-CSHs) can be chemically synthesized using abundantly available, inexpensive materials such as siliceous shale and calcium hydroxide. A-CSHs can serve as a bifunctional adsorption-aggregation agent for phosphate (P i ) recovery from aqueous solution. A-CSHs can also be prepared by soaking recyclable calcium silicates such as concrete sludge and steelmaking slag in a dilute hydrochloric acid solution. Since A-CSHs show high P i removability, settleability, and filterability, they have the potential to offer a simple, cost-effective option to the recovery of P i from P i -rich waste streams. On-site experiments using a mobile, pilot-scale plant have showed that A-CSHs can recover approximately 80% P i from a P i -rich sidestream in a wastewater treatment plant. This chapter describes a simple process for P i recovery from aqueous solution using A-CSHs as a bifunctional adsorption-aggregation agent.