Study On Preparation Of Cigarette-based Carbonaceous Porous Materials And Their Adsorption Properties And Mechanism For Persistent Pollutants

Persistent pollutants refer to harmful chemicals that can persist in the environment and accumulate through the biological food chain.Because of their persistence,high toxicity,bioaccumulation and long-range migration,persistent pollutants pose a huge threat to biological and human health and are urgent.There is an urgent need to develop a cheap,efficient,and anti-jamming adsorbent to treat water bodies containing persistent pollutants.Bisphenol A（BPA）is a typical persistent pollutant.As an important chemical raw material,bisphenol A is widely used and in high demand.The pollution problem is becoming increasingly prominent,which undoubtedly increases the risk of human exposure;Palladium ions as a heavy metal with excellent performance,as another type of persistent pollutant,it is widely used in the automotive,electroplating,and circuit board industries.Due to its large demand,low earth abundance,high hazard,and recycling of palladium ions It seems particularly important.Therefore,bisphenol A and palladium ions were selected as template pollutants in this study.Activated carbon has the advantages of large specific surface area and stable chemical properties.The use of activated carbon adsorption technology to remove persistent pollutants in water has been considered as the most effective and extensive treatment method.It is a widely used adsorption material and widely used in durable Treatment of persistent pollutants.In this paper,waste cigarette butts were selected as raw materials,and a series of methods were used to optimize the preparation of carbonaceous adsorbents.The adsorption properties and mechanism of bisphenol A and palladium ions were studied.The details are as follows:1.For the first time,new cigarette butt-based biomass activated carbons AC-500,AC-600,AC-700,and AC-800 were successfully synthesized by using waste cigarette butts as raw materials through hydrothermal carbonization and heat activation with KOH as an activator.The optimal synthesis conditions are:carbonization temperature is 220 ^oC,C/KOH ratio is 1/4,and activation temperature is 800 ^oC.The theoretical maximum adsorption capacities Q_m of AC-500,AC-600,AC-700 and AC-800 for BPA adsorption are 55,435,699 and 847 mg/g,respectively.Langmuir isotherm adsorption model is more suitable to describe the entire adsorption behavior.Kinetic studies show that the adsorption process is more in line with quasi-second-order kinetics.It exhibits that the adsorption performance of AC-800 on BPA is much higher than that of commercial activated carbons comparison with three commercial activated carbons.In addition,according to literature research,it is found that AC-800 not only has excellent adsorption rate for BPA,but also possess prominent adsorption capacity.Anti-interference experiments show that p H,humic acid,coexisting ions and different water sources have little effect on the process of AC-800 adsorption of BPA.The results show that AC-800 has great potential for remediation in actual water bodies.Recycling experiments show that AC-800 has excellent recycling performance,the BPA removal rate is still as high as 91%even after 8 cycles of use.2.In order to investigate the adsorption enhancement mechanism and adsorption mechanism of BPA on cigarette butt-derived activated carbon,this paper uses previously synthesized AC-500,AC-600,AC-700,and AC-800 as adsorbents.SEM,BET,XRD,Raman,XPS and QSAR quantitative analysis found that the adsorption enhancement mechanism of AC-500,AC-600,AC-700 and AC-800 of cigarette butt-derived activated carbon materials was induced by structural defects.By linearly fitting the maximum adsorption capacity of a series of organics and LOLIPOP index,it was found that there is no correlation between the maximum adsorption capacity of organics and LOLIPOP index,andπ-πinteraction is not the mechanism of AC-800 adsorption of BPA.Through p H effect experiments,salt concentration effects experiments,pyrene adsorption experiments found that hydrogen bonding and electrostatic interactions are not the main mechanism of BPA on AC-800 adsorption.By analyzing the relationship between the molar ratio of O/C and the adsorption capacity,the relationship between the octanol/water partition coefficient and the maximum adsorption capacity,and the effect of different volume fractions of ethanol on the adsorption of BPA on AC-800,it was found that hydrophobic interactions plays a leading role of BPA adsorption on AC-800.By exploring the relationship between polarizability,molar volume,and maximum adsorption capacity,it was found that hydrophobic interactions and dispersion forces play a synergistic role of BPA adsorption by AC-800,and hydrophobic interactions play a dominate role.3.Carbonaceous materials lack effective palladium ion chelating sites.In order to give them better adsorption performance for palladium ions,based on the theory of Hard-Soft-Acid-Base,a compound rich in selenium sites was introduced into the material to prepare efficient palladium ion adsorbent.This study uses hydrothermal method to synthesize composite materials with selenium powder as the selenium source and ammonium molybdate tetrahydrate as the molybdenum source.The optimal synthesis conditions are:the type of carbon source is hydrocar,and the hydrothermal temperature is 140 ^oC.it illustrates that the successful synthesis of materials by SEM,TEM,XRD,etc.The theoretically calculated maximum adsorption capacities Q_m of palladium ions adsorption on Mo Se₂,Mo Se_x/hydrochar-140 and Mo Se_x-140 are 139,833 and 1111 mg/g,respectively.The Langmuir isotherm adsorption model is more suitable for describing the entire adsorption behavior.According to literature research,it is found that the adsorption capacity of Mo Se_x/hydrochar-140 for Pd（Ⅱ）is also very prominent.Through EDS mapping analysis,it reveals that the presence of hydrated carbon has further improved the dispersibility of Mo Se_x,thereby exposing more effective adsorption sites and improving the mass transfer efficiency and adsorption performance of the adsorbent,the presence of hydrated carbon improves the adsorption performance of the adsorbent,which has guiding significance for the synthesis with carbon-based composite materials.