Abstract: The invention is a new composition and process for lanthanum oxide concentrate that is used to significantly reduce arsenic and/or selenium concentration levels in aqueous solutions. The lanthanum oxide concentrate is a mixture of lanthanum oxide and one or more oxides from the following group: neodymium oxide, cerium oxide, parseodymiun oxide, strontium oxide, calcium oxide and sodium oxide. The process of manufacture comprises the steps of sintering the lanthanum oxide concentrate, then washing the resultant media. The process of use is the contact of the lanthanum oxide concentrate with an aqueous solution containing arsenic and/or selenium whereby the lanthanum oxide concentrate removes at least a portion of the arsenic and/or selenium from the aqueous solution.