Controlled removal of ions from aqueous fluid

Methods and systems for removal of ions from aqueous fluids are provided. In certain embodiments, the present disclosure provides a method of removing one or more oxyanions from an aqueous fluid, including the steps of contacting an aqueous fluid containing oxyanions with an aluminum metal whereby aluminum ions are released from the aluminum metal into the aqueous fluid, wherein the one or more oxyanions in the aqueous fluid react with the aluminum ions to form one or more ettringites; controlling a rate of release of the aluminum ions from the aluminum metal; and removing at least a portion of precipitated ettringites from the aqueous fluid.