Removal Of Tetrabromobisphenol A And Heavy Metals By Reduced Graphene Oxide Composite Nanomanganese Dioxide Danomotors

Tetrabromobisphenol A（TBBPA）is widely used in electronic products due to its excellent flame retardant properties,and heavy metal devices must be used to make electronic products.During the accumulation of e-waste,tetrabromobisphenol A（TBBPA）and heavy metal elements will enter the ecological environment through various ways,because their toxic effects pose a threat to the ecosystem and human health.TBBPA treatment technologies include physical,chemical,biological,and currently widely studied advanced oxidation methods,but there are disadvantages such as long treatment cycles,secondary pollution,and inefficient treatment.Methods for heavy metal removal from the environment include physical adsorption,chemical precipitation,and biological methods,but these methods are costly,have long treatment times,and are difficult to recover.Therefore,it is urgent to develop a stable,efficient,easily recyclable,and highly reusable technology for the treatment of contaminants in e-waste.In this paper,TBBPA,a contaminant in e-waste,and heavy metal contaminants were selected for removal.Graphene oxide（rGO）motors and reduced graphene oxide composite nanomotors rGO/MnO₂nanomotors were prepared and characterized using graphene and hydrothermal synthesis.The effects of p H,motor length,motor number,H₂O₂concentration,initial concentration of TBBPA,and burst effect of methanol on the removal efficiency of TBBPA wastewater were investigated,and the removal efficiency of rGO motors and rGO/MnO₂motors for TBBPA wastewater were compared,as well as the repeated composite usability of rGO motor carriers,and the degradation products and degradation mechanisms were analyzed.In the removal of heavy metal wastewater,the effect of p H on the removal rate of low and high concentration heavy metal wastewater was investigated,as well as the effect of different initial concentrations of Pb²⁺on the removal of Pb²⁺by rGO/MnO₂motor,the removal curve of Pb²⁺by rGO/MnO₂motor,and the performance comparison of Pb and Cd removal by rGO motor and rGO/MnO₂motor.The main conclusions were obtained as follows.（1）rGO and rGO/MnO₂prepared by laboratory hydrothermal synthesis are structurally dense black hydrogel nanomaterials.The graphene nanosheets underwen severe folding and bending during hydrothermal synthesis to form a three-dimensional porous hydrogel,and in situ growth of MnO₂into the graphene sheets could be observed,which inhibited the accumulation of graphene sheets on the one hand and increased the catalytic performance of the motors on the other hand.The porous structure of the hydrogel increases the adsorption performance of the motor and the dispersion of the nano-MnO₂.rGO/MnO₂motor in will catalyze the decomposition of H₂O₂to produce oxygen bubbles,and the motor is driven by the oxygen bubbles in a disordered motion.（2）TBBPA removal by rGO/MnO₂motor:The rGO/MnO₂motor has a better effect on TBBPA removal than the rGO motor,and can carry out oxidative degradation reaction along with the adsorption action.The reaction temperature was25℃,p H was 3.0,the motor length was 4mm,the number of motors was 4,and the volume ratio of methanol-water The best degradation of TBBPA was achieved under the condition of 20:80.The removal rate of TBBPA decreased at the initial concentration of 350 mg/L.The acidic environment and low TBBPA concentration can promote the degradation of TBBPA.rGO motor carrier can be repeatedly compounded with MnO₂.in addition,the rGO/MnO₂motor can be easily operated and separated after multiple uses.oxidative degradation of TBBPA occurs through the above three pathways such as intramolecular breakage,debromination,and hydroxylation.（3）Experiment of rGO/MnO₂motor to remove heavy metals:At p H 3.0-8.0,four heavy metals of Cu,Pb,Cd,and Ni were removed,and neutral and alkaline environments were more favorable for heavy metal removal,and the removal efficiency showed Cu>Pb>Cd>Ni.rGO/MnO₂motor did not achieve a good removal effect in the removal of Cr（VI）,and the experiment proved that rGO/MnO₂motor MnO₂motor produces strong oxidation groups that inhibit the removal of Cr（VI）;the initial concentration of Pb²⁺is negatively correlated with the removal rate,and the rGO/MnO₂motor can degrade more than 90%of Pb²⁺solution with 100 mg/L initial concentration within 10 min.rGO/MnO₂motor has a better removal effect on Pb and Cd than the rGO motor.rGO/MnO₂motor will catalyze H₂O₂to generate active groups such as hydroxyl radicals on the surface of the motor and active groups such as hydroxyl（OH·）radicals accelerate the complexation with heavy metal ions,followed by redox and co-precipitation reactions for the final removal of heavy metals.In summary,the rGO/MnO₂motor prepared in this paper can effectively degrade and remove TBBPA and heavy metals from simulated wastewater and has wide application prospects for the removal of halogenated pollutants and heavy metals.