A wicking fiber for use in immobolizing ion exchange resins is described. The filter medium includes at least one fiber having a liquid or solid material disposed on an external surface thereof. The fiber can include structures such as an elongated fiber having multiple lobes with a longitudinally extending internal cavity including an opening from the internal cavity to the outer fiber formed between adjacent lobes. The material, which can be disposed within the internal cavity of the fiber, has a high affinity for dissolved or soluble material in order to strongly attract and retain the dissolved or soluble material, while at the same time not causing a substantial pressure drop across the filter medium.
