Study On The Application Of Activated Carbon Fiber In Wastewater Treatment

Activated Carbon Fiber(ACF)is a kind of novel carbonaceous adsorbent developed in the 60s of the 20^thcentury.Compared with the powder and the granular activated carbon,ACF has its remarkable advantages:extraordinary large specific surface area,enormous adsorptive value,simpler pore structure,special microporous structure,fast adsorption rate and its ease of handing.These structure and characteristics make the application of ACF widespreadly in waste gas and water treatment.In this paper,the adsorption characteristics for pollutants in wastewater by activated carbon fiber(ACF)were studied.For further improving its adsorption capacity.,ACF was modified and the adsorption properties of ACF before and after modification were studied.Viscose ACF was selected as adsorbent and the adsorption capability for adsorbing pollutants in wastewater was investigated in this experiment.The experiment was divided into four parts:1.Characterize ACF:The pore distribution of ACF was analyzed through the adsorption isotherms for nitrogen.The surface function groups and morphology were characterized with the help of SEM photos and XRD.The experiment results showed that the surface of ACF acquires a negatively charge.Its iodine value and specific surface area are 1146 mg/g and 1107 m²/g respectively,and the total pore volume is 0.547 cm²/g.2.The adsorption characteristics for phenol,p-chlorophenol and p-nitrophenol in wastewater by ACF were studied.The adsorption thermodynamic characteristics and mechanism of phenol,p-chlorophenol and p-nitrophenol on ACF were investigated by using the bottle-point technique.The effect factors such as adsorption time,the amounts of ACF and pH on adsorption efficiency have been studied.The results showed that the rate of adsorption was fast.After 1 min.the adsorption amount could reach to 90%of the saturation adsorption capacity,and the absorption equilibrium could be achieved after only 30 minutes.ACF possessed good adsorption properties when pH＜7.The order of removal efficiency were:phenol(87%)＜p-chlorophenol(96%)＜p-nitrophenol(99%).On the same condition,the removal performance for phenol,p-chlorophenol and p-nitrophenol of ACF were more effectively than that of powder activated carbon,which were all under 50%.The adsorption isotherms can be well represented by Dubinin-Radushkevich equation and the adsorption process were physical and spontaneous exothermic reaction.3.ACF was used to remove Pb²⁺,Cu²⁺from solution.The effects of pH,the dosage of ACF and adsorption time have been studied.The results indicated that for Pb²⁺,Cu²⁺,when the temperature was 25℃.the adsorption equilibration time were 90 min and 180 min,respectively.The pH value influenced the adsorption properties of ACF for Pb²⁺,Cu²⁺greatly.The higher the pH value was,the higher the removal rate of Pb²⁺,Cu²⁺was.Kinetic analyses showed that the adsorption activation energy for Pb²⁺,Cu² were 30.92kJ/mol,9.47kJ/mol respectively,suggesting the physical adsorption process.The adsorption isotherms showed that the adsorption process belonged to monolayer adsorption and could be described by Langmuir model well.The influence of temperature on the removal rate for Pb²⁺was little.But for Cu²⁺,the removal rate increased with the temperature increasing.The Free energies of reactions were all negative,which indicated the reactions could occur spontaneously.And the absolute counts ofΔH were all＜30 KJ/mol,which suggested the adsorption of Pb²⁺,Cu²⁺on ACF belongs to physical adsorption.4.Modification of ACF:For further improving the adsorption capacity,the activated carbon fiber(ACF)was modified by ferrous sulfate solution with different condition.The orthogonal experimental method was adopted to determine the best modifying conditions,which were pH value 3,100kg/m³ of the concentration of FeSO₄·7H₂O,the mFeSO₄·7H₂O/m ACF=2.5.3 hours of stirring time.The modified ACF was used to study the adsorption for phosphor-containing wastewater and the adsorption isotherm was determined.The effect factors such as adsorption time,the amounts of ACF and pH on adsorption efficiency have been studied.The results showed the structure of disorder graphite layers of ACF was destoried by modified. Iron compounds were loaded on the surface of ACF,so the specific surface area and negatively charge on modified ACF was lower than ACF.The modified ACF had good property for phosphorus removal.