Synthesis of a novel Fe-Mn binary oxide-modified lava adsorbent and its effect on ammonium removal from aqueous solutions

摘要

Ammonium is strongly related to eutrophication and a key control of eutrophication in aquatic systems, especially in agricultural runoff. In this study, a novel Fe–Mn binary oxide‐modified lava (FMML) granular adsorbent was synthesized for ammonium removal from aqueous solutions by co‐precipitation method. The kinetic data were described by pseudo‐second‐order kinetic model well and intraparticle diffusion had effects on ammonium adsorption. For pH between 4.0 and 10.0, the adsorption efficiency was 80%, and its optimum was recorded at pH 7.0. FMML exhibited strong ammonium adsorption selectivity under the single presence of cations like Na~(+), K~(+), Ca~(2+), and Mg~(2+). The optimum adsorbent dose and particle size were 4 g/L and 3–5 mm, respectively, for an aqueous solution containing 10 mg/L of ammonium under normal conditions (298 K and pH 7.0). Furthermore, the adsorption process was endothermic, following both the Langmuir (iR ~(2)  0.98) and Freundlich (iR ~(2)  0.96) models. Compared with other adsorbents, the FMML can be prepared following a simpler protocol. After 30 times of adsorption–regeneration cycle, the FMML also had a relatively high ammonium adsorption capacity; hence, we see it as a prospective adsorbent for ammonium adsorption from aqueous solutions. Practitioner points Fe–Mn binary oxide‐modified lava with Fe/Mn ratio 3:1 was prepared using co‐precipitation method. Adsorption maximum of modified lava was 20.8 mg/g (298 K and pH 7.0). Adsorption was sensitive to changes in adsorbent dose, particle size, and pH. Inorganic cations decreased ammonium adsorption in order of Na~(+)  K~(+)  Ca~(2+)  Mg~(2+). Mechanisms for ammonium removal by FMML include diffusion, electrostatic attraction, oxidation, and complexation reaction. Preparation and application of FMML.