Microwave-assisted Synthesis Of Fe And Mn Modified ACF For As(V)removal By Adsorption

Arsenic is a very harmful inorganic pollutant in the environment,which has strong toxic effects to the human body and organisms,such as cause acute or chronic arsenic poisoning and even cancer threatening the people's life and health.At present,there is a serious problem that more than one hundred million were drinking arsenic-contaminated water all over the world.In this paper,efficient adsorbents,iron-modified activated carbon fiber and manganese-modified activated carbon fibers?Fe/ACFO and Mn/ACFO?was rapidly fabricated by microwave-assisted heating treatment strategy,which have efficient adsorption performances for As?V?removal.This research explores the best method for the preparation of Fe/ACFO and Mn/ACFO.The best pretreated condition of nitric acid was as following: the concentration is 30 %⁴0 %,oxidation temperature and time are 25? and 2 h,respectively.The optimum conditions for preparing Fe/ACFO: the ratio of ACF to FeSO₄ is 0.50 g to 100 mL,the mass fraction of FeSO₄ is 25 %,the microwave time is 3 min.The optimum conditions for preparing Mn/ACFO: the ratio of ACF to MnSO₄ is 0.50 g to 100 mL,the mass fraction of MnSO₄ is 20 %,the microwave time is 3 min.Fe/ACFO and Mn/ACFO were characterized by scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,X-ray photoelectron spectroscopy?XPS?,Boehm titration analysis and BET analysis.The characterization results showed that rod-like Fe₂O₃ particles were homogeneously anchored on the surface of ACF,which has 14.0 % of iron loading.Many flake-like Mn₂O₃ particles are found to grow on the surface of Mn/ACFO and manganese loading is 25.5 %.The analysis results indicate that the pore volume and surface area of Fe/ACFO and Mn/ACFO were decreased while oxygen-containing groups on the carbon surface were increased.The condition experiments were carried out to investigate the effect of the pH,As?V?initial concentration,dosage,adsorption time and co-existed salt ions on the adsorption.The results indicated that with Fe/ACFO,the residual concentration of As?V?was below the tolerance level(0.01 mg L^-1)at pH=7.0,initial concentration=3.0mgL^-1,dosage=1.0 gL^-1,adsorption time=2 h.While with Mn/ACFO,the residual concentration of As?V?was below the tolerance level(0.01 mgL^-1)at pH=7.0,initial concentration=16.0mgL^-1,dosage=0.8 gL^-1,adsorptiontime=100 min.The presence of salt?NaCl,Na2SO₄,and MgSO₄?showed little effects on the adsorption of As?V?for Fe/ACFO and Mn/ACFO.The study on reaction Thermodynamics and kinetics showed that experimental data were better described by the Pseudo-second-order kinetic model and the Langmuir sorption model.It was found that the adsorption of As?V?on the surface of Fe/ACFO and Mn/ACFO is a spontaneous and endothermic process.The adsorption capacities?qmax?of As?V?on Fe/ACFO and Mn/ACFO were 20.33 mg g-1,46.10 mg g-1,respectively.It is also suggested that the arsenate uptake by Fe/ACFO is conducted by two simultaneous mechanisms:?I?electrostatic interaction on basic ACF,and?II?chemical adsorption for As?V?on the surface of iron oxyhydroxide nanoparticles.The mechanism of As?V?removal by Mn/ACFO could be described by the following two possible processes: adsorption of As?V?onto the surface of the Mn bonding sites and electrostatic attraction.The residual concentration of iron and manganese are lower than the corresponding water quality standards after As?V?removal.