Efficient and practical adsorption of mixed anionic dyes in aqueous solution by magnetic NiFe-layered double oxide

The present research reports the adsorption capacity of magnetic NiFe-layered double oxide (NiFe-LDO) derived from the heat treatment of NiFe-layered double hydroxide (NiFe-LDH) on capturing of single anionic dye and mixed dyes in water. The formation and characteristics of NiFe-LDH and NiFe-LDO were verified by XRD, FT-IR, SEM, BET, VSM and UV-VIS. The obtained NiFe-LDO was mainly composed of NiFe2O4 and NiO phases, which showed strong magnetic property and made the adsorbents easily collected by external magnet. The amounts of the anionic dyes were captured on NiFe-LDO surface more than that on NiFe-LDH surface due to the larger surface area (68 m2/g for NiFe-LDO and 50 m2/g for NiFe-LDH). The maximum adsorption capacity of NiFe-LDO was in the range of 256–313 mg/g and 244–300 mg/g for eliminating the anionic dyes in single and multiple dye solution, respectively. The chemical adsorption affinity of the anionic dyes on the positive-charge surface of NiFe-LDO increased as follows: methyl orange<alizarin red S<orange II<Congo red. This work shows that NiFe-LDO is an efficient and cost-effective adsorbent for eliminating multiple anionic dyes and reusing for several times.