Study On The Charcoal-based Filter For Drinking Water Purification

The issue on drinking water is increasingly severe in China.The filter made of coconut shell activated charcoal(CAC)performs good purifying characteristics.While the price of coconut shell is dramatically climbing up.Bamboo charcoal(BC)and bamboo activated charcoal(BAC)both have good adsorption ability,which makes it possible to use them as an alternative.Based on the study of basic characteristics of three materials,research on the best parameters for producing filter using three materials and comparison of the purifying effects on drinking water three kinds of filters,theoretical and productive evidence were provided for BC and BAC as raw materials to produce filter.The basic properties including industrial analysis,iodine adsorption and pore structure of three raw materials were compared,and the best parameter for filter molding was achieved with response surface methodology(RSM).At the end,the abilities of achieved filters to purify drinking water were contrasted and the microstructure studied.Research showed that:(1)Among the three kinds,BAC had the lowest ash content,3.2% and the highest fixed carbon content,90.8%.BC owned the highest ash content and the lowest fixed carbon content,which indicated it was carbonized to the lowest.The N2 adsorption isotherm was type IV,which interpreted BC had massive micro pores.The N2 adsorption isotherm was the hybrid of type I and type IV,which showed micro pore and medium pore.The specific surface area of CAC was 874 m2/g,which ranked NO.1,BAC 747 m2/g,and the one of BC was lowest,which indicated that the adsorption ability of CAC and BAC was better than that of BC.Element analysis showed that C and O took most in BC,BAC and CAC,and H,S and N only took few.(2)The influences of adhesive addition(AD),moisture content(MC)of raw material and crushing granularity(CG)on filter were all studies with RSM,and the result showed that the parameters should be 10% for AD,10% for MC and 120 mu for CG to achieve the best filter whatever raw material was.For the best filter of BC,the density was 0.588 g·cm-3,iodine adsorption 325mg/g,smash resistance 0.044 MPa and permeability 0.73 m L/min.for BAC,0.615 g·cm-3,727mg/g,0.294 MPa,0.73 m L/min.For CAC,0.608 g·cm-3,829mg/g,0.289 MPa,0.87 m L/min.(3)The experiment of liquid formaldehyde adsorption showed CAC filter was the best,followed by BAC filter and then BC filter.The removal rate of formaldehyde of CAC filter was 77%,BAC filter 63.6% and BC 47%.The experiment of adsorption capacity proved that the CODMn values of purified water by CAC filter,BAC filter and BC filter were respectively 0.6 mg/L,0.9 mg/L and 1.2 mg/L,which all accorded with the requirement of the standard(GB 5749-2006).Trace elements analysis for purified drinking water showed that the best adsorption effect of filters on trace elements was CAC filter,followed by BAC filter and then BC filter.The quantity after purified by the three kinds of filter could meet the requirement in the standard(GB 5749-2006).(4)XRD showed that three kinds of materials all owned good crystal structure.After molded,the main diffraction peaks stayed the same as those of raw materials,which mean there was no chemical reaction in the process of molding.From the result of EPR,the free radical on the surface of BC was strongest,followed by BAC,and then CAC,and during the purifying process,free radical reacted with substances,so to speak,chemical reaction happened.Coupled with the result of SEM,in the process of drinking water purification with filter,both physical and chemical reaction exist.