| Recent years,nanoparticles inevitably release into the ecological environment with its widespread application,which have a potential impact on human health and the environment.Natural organic matter(NOM)exists in surface water.Different kinds of NOMs have different effects on the surface properties,mobility and deposition behavior of nanoparticles,which will inevitably affect the removal efficiency of nanoparticles in water treatment process'To solve this problem,this study selected three typical NOMs including bovine serum albumin(BSA),sodium alginate(SA)and humic acid(HA),and investigated the effects of different NOMs on the surface charge,hydraulic particle size and soluble aggregation state of silver nanoparticles(AgNPs),Meanwhile,the effects of different NOMs on the removal efficiency of AgNPs in adsorption and coagulation processes were studied to further clarify the effect of NOMs on the behavior of AgNPs in water treatment process,which was of great significance to the ecological risk and health risk control of nanoparticles.The main research contents and conclusions were summarized as follows:1.Different AgNPs simulated water samples were prepared by mixing BSA,SA and HA with AgNPs collosol,and their surface charge,hydraulic particle size,dissolution and aggregation were characterized by Zetasizer Nano and ultraviolet spectrophotometer.The results showed that BSA,SA and HA could increase the hydrodynamic particle size of AgNPs.Under acidic conditions,the hydrodynamic particle size of AgNPs in SA water sample was the largest.HA and SA can enhance the surface electronegativity of AgNPs,while at pH=4,the surface potential of AgNPs in BSA water sample increased to isoelectric point.Moreover,by UV-visible absorption spectroscopy,it was known that BSA and HA were more likely to promote the dissolution of AgNPs than SA.2.Using activated carbon adsorption process to remove AgNPs from water samples,the study discussed the effects of BSA,SA and HA on the adsorption efficiency and kinetics of AgNPs,and preliminarily clarified the adsorption mechanism of AgNPs in presence of NOM.The results showed that BSA had a strong inhibitory effect on the adsorption efficiency of AgNPs.When the concentration of BSA was 10 mg/L,the removal efficiency of AgNPs was only 23%,and most of AgNPs adsorbed on activated carbon existed in the form of zero-valent silver.When the hardness of CaCO3 increased to 450 mg/L,the removal efficiency of AgNPs could reach 88.6%.HA had less inhibition on the removal of AgNPs,which promoted the dissolution of AgNPs during the adsorption process,and made AgNPs adsorbed mainly on the surface of activated carbon in the form of Ag+.When the water sample changed from acidic to alkaline,the effect of HA on AgNPs changed from inhibition to promotion.In comparison,SA had little effect on the adsorption of AgNPs under different water quality conditions.3.Using coagulation process to remove AgNPs from water samples,the study discussed the effects of BSA,SA and HA on coagulation efficiency and coagulation kinetics of AgNPs,and preliminarily clarified the coagulation mechanism of AgNPs in presence of NOM.The results showed that BSA.SA or HA could inhibit the coagulation efficiency in the treatment process with polyaluminium chloride(PAC)as coagulant.Among them,BSA had the strongest inhibiting effect,followed by HA,and SA had the weakest effect,especially in low dosage conditions.When the dosage of PAC was less than 8 mg/L,the removal rate of AgNPs in BSA water sample was less than 20%.When the water was under weak alkaline conditions,the removal efficiency of AgNPs decreased due to the weakening of electroneutralization,but the presence of NOM could weaken the influence of alkaline environment on AgNPs.In addition,NOM had some influence on coagulation kinetics during AgNPs treatment process.The average particle size of AgNPs flocs in SA water sample was the largest.When the dosage of PAC was 10mg/L,it could reach about 3 times of AgNPs flocs in HA and BSA water samples,but the recovery ability of AgNPs flocs in SA water samples after crushing was the worst. |
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