| With the rapid development of modern society,the problem of water source pollution has become increasingly serious.Organic matter represented by humic acid?HA?and microalgae and their secretions?AOM?represented by Microcystis aeruginosa?MA?are potential threats to the safety of drinking water quality,which pose a severe test to the purification process of drinking water.Most of the water treatment agents currently used are at risk of secondary contamination in the drinking water treatment link.For example,in the disinfection link,the use of disinfectant can convert the intracellular organic matter?IOM?and extracellular organic matter?EOM?secreted by MA and HA in the water into disinfectant by-products?DBPs?with“three causes”performance.Existing processing technologies have various limitations.Therefore,research and development of new materials with high efficiency,low cost,low toxicity or non-toxicity has become a hot spot in the field of water treatment.HA and MA were the target pollutants in this study.Magnetic chitosan grafted polyacrylamide?MC-g-PAM?was prepared by one-step in situ coprecipation.The purification efficiency of HA and MA was investigated respectively.FTIR,XRD,SEM,XPS,BET and other technical means were used to characterize its physical and chemical properties and explore its adsorption mechanism.Taking the adsorption capacity of HA and the removal rate of MA as the preferred indicators,the optimal preparation scheme of MC-g-PAM was determined by orthogonal test:the mass ratio of Fe3+to chitosan was 3:1,the mass ratio of chitosan to acrylamide was 2:1,the dosage of epichlorohydrin was 3 mL,and the crystallization time was 2 h.The MC-g-PAM synthesized according to the optimal preparation scheme is coated with acicular polyacrylamide with a cross-sectional diameter of 50-70 nm and magnetic chitosan particles with a diameter of 120-300 nm,with more surface pores.There were more mesopoles and macropores,fewer micropores.It is mainly composed of Fe,O,C and N elements,accounting for 30.7%,41.5%,25.9%and 2.9%,respectively.MC-g-PM has a specific surface area of 27.1 m2·g-1 and a specific saturation magnetization of 9.63 emu·g-1.MC-g-PAM has a good purification effect on HA in water,and the purification mechanism is chemical adsorption.The dosage of MC-g-PAM was 0.3 g·L-1,and the pH of the solution was 7.0,which the treatment effect was the best.With the increase of MA concentration from 0.356 mg·L-1 to 2.869 mg·L-1,the removal rate of HA decreased from 80.70%to 17.54%.In the absence of MA,the removal rate of MC-g-PAM to HA with a concentration of 5 mg·L-1 was 91.72%.The adsorption process conforms to the Langmuir isotherm and is monolayer adsorption.The theoretical saturated adsorption capacity can reach 120.77 mg·g-1.The adsorption process conforms to the pseudo-second-order adsorption kinetics rate equation.Within the first15 minutes of the adsorption reaction,the adsorption amount of HA reaches more than half of the equilibrium adsorption amount,and it is a spontaneous,disordered endothermic process.After five consecutive adsorption–desorption–regeneration cycles,the adsorption rate of MC-g-PAM remained above 70%.MA in water can also be removed by adsorption from MC-g-PAM.The treatment effect was best when the dosage of MC-g-PAM was 0.3 g·L-1 and the pH value of the solution was 37.The presence of HA has a certain inhibitory effect on MC-g-PAM removal of MA,and the higher the HA concentration,the stronger the inhibition.With the increase of HA concentration from 5 mg·L-1 to 30 mg·L-1,the removal rate of MA decreased from 71.05%to 52.66%,while in the absence of HA,the removal rate reached 84.74%.The adsorption equilibrium of chlorophyll a in MA was studied to reflect the adsorption equilibrium of MC-g-PAM on MA in water samples.The adsorption process also conforms to the Langmuir isotherm.The Langmuir equation shows that the maximum adsorption capacity of MC-g-PAM for chlorophyll a in MA is 301.99?15°C?,318.63?25°C?and 341.85?35°C??g·g-1.The adsorption process conforms to the pseudo-second-order adsorption kinetic rate equation and is a spontaneous,disordered endothermic process. |
PDF Full Text Request