Preparation Of Sargassum Horneri Based Activated Carbon With Composite Activator And Its Adsorptive Removal Of Cr(?)in Alkaline Condition

Activated carbon is one of the most commonly used adsorbent,which has a large specific surface area and developed pore structure.The capacity of the adsorption of activated carbon is not only connected with its pore structure,but is also related to the chemical property on its surface.The current research and literature have declared that the activated carbon shows great adsorption property under acidic condition,while performs below expectation in alkaline condition.A lot of studies have testified it.Relevant researches indicate that by doping composite salt solution onto activation carbon as activation agent would enhance the adsorption efficiency to Cr???in alkaline condition.Sargassum Horneri based activated carbon was prepared by Sargassum Horneri as raw material,and zinc chloride along with ferric chloride hexahydrate as composite activator,it could improve the removal rate of Cr???in the alkaline conditions.Effects of activation temperature,time and impregnation ratio?Sargassum Horneri/composite activator?on the yield and the removal rate of Cr???on SAC-CA were tested by using orthogonal experiments.The optimized SAC-CA was characterized with Scanning Electron Microscopy,Surface Area Analyzer and the Boehm titration method.The single factor experiments were useded to explore the effect of pH,dosing quantity,the initial concentration of Cr???and temperature on the removal of Cr???by the optimized SAC-CA.With glutaraldehyde solution as crosslinking agent,doping composite salt solution onto activation carbon to explore the removal of Cr???in the different alkaline systems.Meanwhile,The application of SCA-CA in aquaculture wastewater and the regeneration performance of SCA-CA were investigated.The results indicated that:?1?The optimal preparation condition of SAC-CA is the temperature at 500?,activation time for 3 h and impregnation ratio at 3:1.Under this condition,the yield of SAC-CA was 33.15%,the removal of Cr???was 98.22%,The specific surface area of SAC-CA was 1277.23 m²·g^-1,the average pore diameter was 9.88 nm.The total content of the acidic functional groups containing oxygen was higher than that of the single activator.The content of phenolic hydroxyl group and carboxyl group was the main component in the acidic functional groups.?2?Within the pH range of 7¹0,elevating temperature,increasing reaction time and increasing the dosage of SAC-CA is propitious to the removal of Cr???by SAC-CA.For the Cr???solution of which initial concentration was 20 mg·L^-1,after adding 0.20 g SAC-CA and react in thermostatic waterbath for 24 h,the removal of Cr???by SAC-CA could reach to almost98.08%when pH was controlled at 7,yet the removal rate could still reach to 95.04%when pH was controlled at 10,which shows that SAC-CA can effectively remove Cr???in wastewater in alkaline conditions.?3?Conditions of chitosan modified activated carbon are as follows:the ratio of chitosan to SAC-CA is 1:3,the dose of glutaraldehyde solution is 5 mL·g^-1?chitosan?,temperature is 70?and the time is 2 h.Within the pH range of 7¹0,the modified activated carbon is propitious to the removal of Cr???and then removal rate of Cr???decreases slowly with the increase of pH.?4?When the cycle number is less than 3 times,the Cr???has obviously removal effect,while cycle number is more than 3 times,the removal efficiency of Cr???is low.The regeneration effect on the removal of Cr???by the NaOH solution is better.It shows that the NaOH solution can exert positive effect on the regeneration of SAC-CA.?5?After treatinig aquaculture water with SAC-CA,the concentrations of active phosphate,ammonia nitrogen,nitrite and COD are lower.The concentrations of Cu and Hg ions had little change,while As and Cr???ions changed a lot with the increase of SAC-CA.The removal of As and Cr???were more than 50.00%and 90.00%,respectively.