Study On The Dissolution Rule Of Organic Water Purification Material And Its Coupling Effect On Drinking Water Safety

In recent years,due to different levels of raw water pollution and people's pursuit of high quality of life,people put forward higher requirements for drinking water quality,therefore,household water purifiers are widely welcomed.Activated carbon materials are used in water purifiers because of their large specific surface area,developed pore structure and obvious adsorption characteristic.However,when contacting with water,the organic matter dissolved in the material will interfere with the secretion process of normal substances in human body,and generate disinfection by-products(DBPs)with the residual chlorine in the water.The dissolution of refractory and accumulative metals directly or indirectly affects human health.Therefore,organic water purification materials are particularly important for the safety of drinking water.In this study,element analysis by combustion method,ultrasonic extraction + headspace-mass spectrometry(GC-MS)and microwave digestion + inductively coupled plasma mass spectrometry(ICP-MS)were firstly used to qualitatively and quantitatively detect elements and compounds contained in various organic water purification materials.Then,the content of anions and other dissolved substances in standard immersion water were determined by ion chromatography,and the content of organic substances in chlorine-free immersion water were determined by purge,capture and GC-MS.Finally,the effects of temperature and p H of different soaking water on metal dissolution were studied.The conclusion of this study was as follows:The content of N,C,H and S in coconut shell activated carbon,carbon rod,carbon fiber and KDF + activated carbon were detected by element analysis with combustion method,and EDS analysis was conducted.The results showed that the content of C in the four materials was the highest,ranging from 68% to 88%,followed by the higher content of O and H,which may be due to the large number of oxygen-containing functional groups in the materials,leading to the higher content of C,H and O.Some N was detected in the carbon fiber,which may be because the carbon fiber also contains some nitrogen-containing functional groups.The existence of these functional groups maked the water purification materials have strong adsorption and catalysis.To establish ultrasonic extraction + headspace-GC-MS method for determination of organic compounds in three water purification materials: coconut shell activated carbon,carbon rod and carbon fiber.Acetone was used as the extraction agent for ultrasonic extraction of materials,and the materials and extracts were analyzed by headspace-GC-MS respectively.The results showed that there were more than 50 kinds of organic compounds in the three materials,but most of them were low in content.The phthalate ester content was high,which may be added into the material as plasticizer and pore expanding agent.By comparing the relevant domestic and foreign standards,the metal testing items in the standards were rolled together,and 18 metal elements such as aluminum(Al),chromium(Cr),manganese(Mn)and mercury(Hg)were summarized to be tested.A method for determination of 18 metal elements in 4 materials by microwave digestion + ICP-MS was established.The results showed that the digestion is complete and the effect is obvious.All the four materials did not contain Pb,Be and Hg,and the other 15 metal elements were detected to different degrees.The main metals with high content were Al,Zn and Ba.Among them,the content of Cu and Zn in KDF + activated carbon material was relatively high,and the proportion was about 1:1.Therefore,the model of KDF in the material was presumed to be KDF55.The soaking experiments of the above four materials in the standard soaking water with p H 8,hardness 100mg/L,effective chlorine 2mg/L and the standard soaking water without residual chlorine were studied.The indexes of p H,oxygen consumption and TDS of the standard soaking water were detected.The results showed that the increase of p H,TDS,turbidity,CHCl3,Al,Zn and Ba in the water after 24 h immersion of the four materials exceeded the standard value,and the dissolution of CH2Cl2 in carbon fiber and KDF + activated carbon exceeded the standard value,and there were certain health risks to human body after drinking.The effects of immersion water temperature and p H on metal dissolution of 4 materials were studied.The results showed that high temperature increases the thermal motion of metal,speeds up its dissolution rate,and maked it easier to dissolve metal.The dissolution of Al,Ba and Ni exceeded the standard when the temperature was higher.The dissolution of different metals in water varied greatly with the change of p H,which could be divided into the following categories:(1)The lower the p H,the easier the precipitation;(2)The higher the p H,the easier the precipitation;(3)At p H=7,the amount of dissolution was the least,and it was easy to precipitate in acidic and alkaline water.The dissolution of some metals in water with different p H values exceeded the standard.