Preparation and properties of ion‐exchange membranes prepared by the radiation‐induced grafting of a styrene/acrylic acid comonomer onto low‐density polyethylene

The preparation of ion‐exchange membranes by the direct radiation grafting of acrylic acid and styrene onto low‐density polyethylene was studied. The effects of the grafting conditions, such as the comonomer composition and concentration and the irradiation dose, on the grafting yield were also investigated. The swelling behavior, ion‐exchange capacity, structural changes, and thermal properties of unsulfonated and sulfonated membranes were studied. The crystallinity decreased with grafting and sulfonation, but the chemical and thermal stability was improved by sulfonation. The removal of some toxic heavy‐metal ions—Cd 2+ , Pb 2+ , and Zn 2+ —was studied. Some factors that influenced the metal‐ion uptake were studied. The metal‐ion‐uptake results showed that the membranes could be used for the adsorption of the investigated metal ions and had an affinity toward Pd 2+ ions in a mixture. The regeneration of the membranes was carried out by a treatment with 1 M HNO 3 , and the membranes were used several times with high efficiency. Thus, the membranes may be suitable for pervaporation or vapor permeation to separate wastewater because of their hydrophilicity.