Preparation of organic acid anion-modified magnesium hydroxides by coprecipitation: A novel material for the uptake of heavy metal ions from aqueous solutions

New layered magnesium hydroxides whose brucite layers had been bridged with malate²⁻ and tartrate²⁻ were prepared by dropwise addition of Mg(NO₃)₂ to malate and tartrate solutions at a constant pH of 10.5. Malate²⁻ and tartrate²⁻ may have been also absorbed on the surfaces of hydroxides. In the case of using citrate solution, Mg(OH)₂ absorbed with citrate³⁻ was produced. These materials were found to take up Cu²⁺ rapidly from an aqueous solution at pH 5.0. Copper uptake by precipitates is attributed to the formation of chelate complexes of Cu²⁺ with citrate³⁻, malate²⁻, and tartrate²⁻.