A composite material for use in water treatment. The composite material includes a porous matrix including a resin capable of retaining a catalyst and magnetic material therein, and includes a density regulating portion disposed therein. The catalyst is capable of facilitating a chemical reaction involving a contaminants in the water. The magnetic material and density regulating portion can be used to separate the composite material from treated water. Systems and methods of use involving passive water treatment, continuous water treatment, solar light exposure, UV light exposure, and electrochemical cells, employing photochemical, electrochemical, and photoelectrochemical reactions are described. Methods of manufacture are described.