Study On Preparation And Process Of Bamboo Charcoal Used In Drinking Water

Bamboo charcoal is a product pyrolysised by bamboo under oxygen-free or anoxic conditions,and its industry has begun to take shape in our country,various products had been developed so far.But in the field of bamboo charcoal applied to drinking water,the relative researches lag behind the market.There is few report on bamboo charcoal of its heavy metal content,mineral content,applications of drinking water and its action mechanism.The production and application theoretical basis of bamboo charcoal for drinking water would be provide through these studies.The bamboo charcoal were prepared in the paper,carbonized by moso bamboo(Phyllostachys pubescens)of various site conditions,longitudinal positions,and ages,under the conditions of carbonization temperature 650 ℃/750 ℃ and reaction time 3 h/5 h,according to the quadrature multiplication method in the mechanical carbonizing kiln.The physical and chemical properties,including ash,volatile matter,fixed carbon,density,the specific surface area and dissolution pH value,and trace element content had been tested,analysis and compared,using ASAP2020,ICP-OES and other instruments,and the effect of each factors and their interactions was obtained.Then several groups of bamboo charcoal with differ heavy metal content were screened out for drinking water application test.The optimum process of bamboo charcoal applied to drinking water were obtained,while factors of bamboo charcoal and drinking water proportion,boiling time,cycle number,different water,boiling or normal temperature impregnation and so on were considered in the test.The changes of bamboo charcoal functional groups,microstructure and crystal structure after boiling water were analysis by FTIR,ASAP2020,VHX-1000 and XRD,and some preliminary exploration on action mechanism of bamboo charcoal applied to drinking water were carried out.The results show that: there were different effects on bamboo charcoal physical and chemical properties and trace element content of different factors.Bamboo charcoal applied to drinking water,is mainly affected by the dissolution of major elements and tars,and few related to bamboo charcoal heavy metal content,it almost did not dissolve in water.(1)Under the experimental conditions,the ashes,volatile and fixed carbon of bamboo charcoal were affected in various degrees by carbonization process,primary material conditions and its interactions.The ash content would be less when no cultivated top section of bamboo carbonized at 750 ℃/3 h;The volatile would be less at reaction time of 5 h;the fixed carbon would be more at carbonization temperature of 750 ℃ than 650 ℃.The bamboo charcoal density were among 0.367-0.705 g·cm-3,mainly related to the longitudinal positions of bamboo.The bamboo charcoal specific surface area is significantly affected by carbonization temperature,also related to the longitudinal positions and reaction time,it reached a maximum when top section of bamboo carbonized at 750 ℃/3 h.The dissolution pH values of bamboo charcoal were among 7.02-9.57,both were alkaline,and suitable for the application on drinking water.(2)The Arsenic(As),Lead(Pb),Cadmium(Cd),and the major elements content of bamboo,including Potassium(K),calcium(Ca),sodium(Na),magnesium(Mg),phosphorus(P),sulfur(S),increased by age and increased from top section to basal section,also closely related to its soil.These factors were in the descending order of influence degree were site conditions,longitudinal positions,and ages;They were also found to be decreased in some degree after carbonization and were affected in various degrees by carbonization process,primary material conditions and its interactions.The As、Pb、Cd content would be less when no cultivated top section of bamboo carbonized at 750 ℃/3 h.The major elements content would be more when basal section of bamboo carbonized at 650 ℃/5 h.(3)When tap water were boiled or continued boiled,brewed,impregnated with bamboo charcoal,or recycle use bamboo charcoal,or use ultra-pure water and mineral water,its index of trace elements content were in line with standard for drinking water GB 5749-2006.The major elements and tars content increased after tap water were boiled or brewed with bamboo charcoal,the best bamboo charcoal and drinking water proportion would be 1:75.With the increase of immersion time or boiling time,trace elements and tars content increased.It would be better for drinking before impregnated 3 h;and boiling time no more than 30 min.When bamboo charcoal was recycle used,the tars dissolved less,it could be recycle used for at least 4 times.The adsorption and dissolved amount of trace elements content were differ from boiling different water with bamboo charcoal,but both dissolved major elements and few tars,then the chroma and turbidity of water rised a little,but they were in line with GB 5749-2006.The residual chlorine were also adsorpted while boiling with bamboo charcoal.(4)Bamboo charcoal functional groups were analysis by FTIR.And there may be associated-OH in bamboo charcoal,it may formed-OH2+ with H+ in water under acidic conditions,then chemical adsorption occurred.It effects little on bamboo charcoal chemical structure while boiling with water.The pore structures were characterized by ASAP2020 and VHX-1000.Bamboo charcoal surface area rised,average pore size become smaller,pore volume increased after boiled water.And some cracks had been founded,they could be mesopore and micropore,which played a major physical adsorption in all pore structures.Analysis by XRD shows that,there were little changes in bamboo charcoal while applied to boil water.Maybe its changes were mainly physical changes,and a little chemical changes.So bamboo charcoal could be cyclely used in drinking water.Comprehensive analysis of the physical and chemical properties,trace elements content and drinking water applications test in this study,the best production process of bamboo charcoal for drinking water were no cultivated basal section of bamboo carbonized at 650 ℃/5 h,and it can be used in ultra-pure water,mineral water or tap water,application methods could be boiling or brewing or impregnating,the bamboo charcoal and drinking water proportion should be 1:75,boiling time no more than 30 min,cycle number more than 4,brewing no more than 3 h.