The Research Of Defluoridation Mechanism With Calcium Modified Biochar And Integrated Equipment For Defluoridation And Regeneration

Biochar represents a certain potential in environmental protection area as a new functional material.But biochar for fluoride remval was rarely reported at domestic and foreign.The paper showed an effective,low-cost adsorbent and equipment for defluoridation in countryside.It has an theoretical and practical signifance in waste resources recycle and fluoride removal from high fluorine water.The study was to develop a calcium modified biochar derived from peanut shell and study its potential for fluoride remval.No.1 biochar was direct carbonization,No.2 biochar was modification with CaCl₂ before carbonization,and No.3 biochar was by modification with CaCl₂ following carbonization.The preparation technique of No.2 biochar is beneficial to fluoride remval.The biochar was well modified with 30%CaCl₂,1:10 solid-liquid rate,24h and showed the highest percentage fluoride removal and adsorption capacity?86.8.1%and1.32mg/g,respectively?under 60min,0.5g biochar,100mg/L fluoride and pH 5-7.The adsorption mechanisms of Ca²⁺-modified biochar were confirmed by adsorption isotherm,kinetic studies,SEM images,energy spectrum,calcium cleaning and FTIR analyses.The mechanisms include surface adsorption,calcium loaded onto the biochar,Ca-F reaction,the functional groups.The good performance of No.2 biochar for de-fluoridation was due to the calcium loaded onto the biochar and the changed functional groups.Ca-F precipitation reaction and only C-H was main method for No.3 biochar.Calcium modification before carbonization is an efficient technique for calcium load and defluoridation.The regeneration conditions and mechanisms of NaOH and ultrasonic regeneration were studyed.It indicated ultrasound was beneficial to regeneration,but NaOH ultrasonic regeneration lead to secondary pollution and high cost.The best regeneration method is high-purity water ultrasonic regeneration at 100W and 15min.SEM,energy spectrum,particle size and FTIR analyses revealed that existence of NaOH had serious effect on surface,loaded calcium content,particle size and functinal groups.High-purity water ultrasonic regeneration had less effect on these.It was beneficial to fluoride remval and repeated regeneration.Colum experiment results showed carbon heigh and flow rate have influence on defluoridation,but carbon heigh play main role in defluoridation.And the optimum flow rate is 5 mL/min and the optimum column height is 10cm.Defluoridation and regeneration integrated equipment operation results showed when the output water is more than 4.8L,average fluoride remval efficiency was less than 80%.Then high-purity water Ultrasonic regeneration was conducted.Repeated operation showed average fluoride remval efficiency was stable.