Study On Treatment Process Of Nitrophenol Wastewater

Nitrophenol compounds are an important class of fine chemical intermediates.With the rapid development of industry,the amount of these intermediates is increasing,resulting in a large amount of industrial wastewater containing nitrophenol pollutants.The wastewater has the characteristics of high chromaticity and high biological toxicity,which poses a great threat to the natural environment and human health.Therefore,it is of great significance to treat nitrophenol wastewater.Among many treatment methods,adsorption method is widely used because of its advantages of simple operation and high treatment efficiency.Porous carbon adsorbents often have excellent specific surface area and rich pore structure,and have excellent adsorption performance for nitrophenol pollutants.The production of traditional porous carbon usually uses biomass,petrochemical products and coal as raw materials,which consumes a lot of fresh resources and does not conform to the principle of green sustainability.In this paper,the strategy of"treating waste with waste"was adopted.An in-situ N,O,S co-doped porous carbon adsorbent was prepared by using solid waste in chemical production,and it was used for the efficient removal of nitrophenol pollutants in wastewater.In this study,M waste residue was collected from the rubber accelerator M production workshop as a precursor.Because the waste residue contains a large amount of N,O and S elements,it has a unique advantage to prepare heteroatom co-doped materials.In this paper,carbon materials were prepared by one-pot method.Among various chemical reagents,K₂CO₃has the best effect.At 900°C,when the alkali residue ratio is 1:1,the material has an ultra-high specific surface area of3095.34m²/g and an ultra-large pore volume of 1.97cm³/g.After carbonization,the K atoms and K oxides in the pores of the material can be cleaned by deionized water,and the activator can be recovered by evaporation crystallization.The properties of the materials prepared by using the activator for 6 times are completely consistent,and the whole preparation process is clean and environmentally friendly.Due to the use of zero-cost carbon precursors,the use of water instead of dilute hydrochloric acid,and the recovery of activators,the material has a very low preparation cost.The cost accounting found that only 14.25 yuan per kilogram of adsorbent is required.The ultra-high specific surface area,abundant pore structure and the modification of various polar functional groups of N,O and S together created the excellent adsorption performance of the material.Under the condition of solution concentration of 500 mg/L and carbon addition of 0.4 g/L,the equilibrium adsorption capacity of MHPC-900 for ONP,PNP and DNP was 823.16 mg/g,677.73 mg/g and 977.66 mg/g,respectively.Adsorption isotherms and kinetic simulations showed that the adsorption of nitrophenol molecules on the surface of the adsorbent was more consistent with the Freundlich multi-molecular layer adsorption and PSO model.The intramolecular diffusion data showed that the adsorption rate was not only controlled by the intraparticle diffusion step.Thermodynamic data show that the adsorption process can proceed spontaneously,and the spontaneous degree of DNP is higher.The adsorption is an exothermic reaction,and low temperature is more conducive to adsorption.DFT molecular simulation results show that the doping of three heteroatoms will enhance theπ-πweak interaction force between nitrophenols and carbon surface and hydrogen bond electrostatic attraction,and improve the adsorption performance of adsorbents for three nitrophenols.The results of dynamic adsorption showed that lower solution flow rate and initial concentration were more conducive to adsorption.When the solution flow rate was 5m L/min and the initial concentration of the solution was 100 mg/L,the dynamic adsorption capacities of the three nitrophenols were 675.44 mg/g,587.54 mg/g and726.11 mg/g,respectively.Compared with commercial carbon adsorbents,MHPC-900has greater adsorption capacity.After desorption with anhydrous methanol,the specific surface area and pore volume of MHPC-900 could be completely recovered,and the dynamic adsorption capacity did not change in four consecutive dynamic adsorption experiments.This fully demonstrates that MHPC-900 is an efficient adsorbent with stable structure and performance,which can be recycled many times.