Influence Factors and Optimization of Preparation of Magnetic Multi-walled Carbon Nanotubes Coated Calcium for Removing Humic Acid from Aqueous Solution

Abstract

Multi-walled carbon nanotubes was magnetized with hybrids of iron oxides and modified with calcium by chemical co-precipitation method. The influence factors of preparing magnetic multi-walled carbon nanotubes (MWCNTs) coated calcium on removing humic acid from water were studied, and the preparation conditions were optimized. The results showed that the higher mass ratio of MWCNTs to Fe3O4 produced the better effect of removing humic acid, when the mass ratio of MWCNTs to CaCl2 was from 3:1 to 1:3, the removal rate of humic acid was higher than 85%. With the temperature increasing, the removal rate of humic acid first increased to the highest at 60℃, subsequently decreased until to temperature 75℃, afterward changed little .The removal rate rose before stirring speed reached 300 r/min then declined with the stirring speed increasing. In comparison, the mole ratio of Na2CO3 to NaOH, reaction time and aging time had little effect on removal of humic acid. The optimal conditions of preparing magnetic MWCNTs coated calcium for removing humic acid at concentration of 20mg/L from water were that the mass ratio of MWCNTs/Fe3O4 and MWCNTs/CaCl2 were 2.5:1 and 2:1, respectively, mole ratio of Na2CO3/NaOH was 5:3, reaction temperature was 60℃, stirring speed was 400 r/min, the reaction time and aging time were 30 min respectively. The product prepared in the optimal conditions removed 94.21% of humic acid from solution after screened by 200 mesh sieve.