Adsorption Of Nitrobenzene From Aqueous Solution By Poplar Leaves

In recent years,nitrobenzene pollution events have often occurred.Nitrobenzene is difficult to degrade effectively in nature, and we often need to use such processes as adsorption, advanced oxidation technology.In order to achieve the recycling of forestry waste-poplar leaves,we explored the adsorption characteristics of poplar leaves for NB under different conditions through grinding into powder, granulating preparation,modification,and combination with other process, and the effective technical parameters for nitrobenzene adsorption were determinded.The main research results are as follows:(1) Poplar leaves have the main constituent elements O, C, Si, Ca, K, etc., which C is at more than 30% in weight. It is found that poplar leaves have abundant pore inside by electron microscopy scans, which provides favorable channels and gap to absorption of NB in water by poplar leaves.(2)At 20°C,to treat 10mg/L NB wastewater through adding 20g/L poplar powder or forming particles,the adsorption rate is 62.7% and 59% respectively. Adsorption process of powder,granules were better conform to the level of adsorption dynamics model,quasi secondary adsorption kinetics model;Adsorption isotherm of them are much more in line with the Langmuir in line with the Langmuir isotherm equation,and the adsorption process is exothermic.This showed that poplar powder, granules and nitrobenzene molecules interact primarily through monolayer adsorption.After desorbing poplar powder and granule for 6 times,the adsorption rate has been for the first two-thirds of adsorption,3/4.(3)Making use of phosphate modification,I made an influence experiment of three factors that are modification temperature,dosage and modifier concentration. The rerults show that the best impregnation concentration,dosage and temperature is 2mol/L,15mL/g and 25°C.According to the static adsorption experiment of modified poplar leaves,I found that at 25°C,adding 35g/L poplar powder or forming particles to 10mg/L NB wastewater,the adsorption rate is 95% and 83% respectively. Their adsorption process has good fitting with quasi secondary adsorption kinetics model,and isothermal adsorption conforms to the Freundlich equation.It is found that the main role on adsorption is hydroxyl groups through analizing the infrared spectrum of modified poplar leaves.(4)The adsorption experiment proceeded after carbonizing poplar leaves under 300°C that concluded that adsorption rate can reach 91% and 80% respectively more than the less carbonized before by about 30% and 15%.The two adsorption processes are well in line with the Langmuir isotherm equation and the Freundlich isothermal equation.(5) In adsorption experiments associated with activated carbon, 4 g/L of the activated carbon powder and more than 15g/L of poplar powder need to be added,and to particles adsorbent, 10g/L of the activated carbon particles and at least 20 g/L of poplar leaves shape particles are added into 40 mg/L of nitrobenzene wastewater reaches to reach the national emission standards.In ozone and poplar leaves adsorption experiments, in order to make 100 mg/L nitrobenzene wastewater reach the national emission standards, firstly to adjust pH to 10, then make aeration oxidation under 35 ° C for 35 min, finally adding 30g/L poplar powder or 40g/L poplar granule for adsorption.To sum up, poplar leaves have a good ability to remove nitrobenzene that are suitable for low and medium concentration of nitrobenzene wastewater.Especially after the modification or carbonization, poplar leaves have a stronger adsorption performance.In the treatment of wastewater with relatively high concentrations of nitrobenzene, poplar leaves can be used with activated carbon absorption or ozonaion to meet the national emission standard.