Modification Of Corn Straw And Its Adsorption Mechanism For Oxytetracycline In Water

There is a wealth of straw resource in China,but most of the straw has not been reasonable and effective used,resulting in a large number of waste and serious environmental pollution.With the development of society,oxytetracycline had been widely used.The direct discharge of waste water containing oxytetracycline had been resulted in pollution of water and soil,and posed a serious threat to human health.Based on the summary of the situation of comprehensive utilization of corn straw,its harm and related wastewater treatment technology containing oxytetracycline at present,the corn straw is modified by etherification,and prepared adsorbents with good performance.It not only solves the problem of oxytetracycline contamination in water,but also opens up a new way of comprehensive utilization of corn stalks.The optimum modification conditions and main influencing factors are determined by single factor experiments and orthogonal experiments in the paper.The best modification condition was the dosage of corn stalk,the dosage of DMF,the dosage of pyridine and the dosage of dimethylamine were 4g,30mL,10mL,25mL respectively,the reaction time of the first stage,the second stage and the third stage were 60min,60min,180min respectively;the reaction temperature in the three stages was 100?.Among them,the dosage of pyridine has the mostly significant effect on the modification results.The removal rate of oxytetracycline by modified corn straw under the optimum conditions is 76%higher than that by unmodified corn straw.The structure morphology and crystallinity of corn straw before and after modification are characterized by scanning electron microscopy(SEM)and X-ray diffraction(XRD).The results showed that the structure of modified corn straw was close and the interface was clear.The natural holes and cracks on straw surface disappeared,accompanied by the appearance of large number of irregular sheet folds.In addition,the crystallinity of corn straw was also significantly reduced after modification.The adsorption of modified corn straw on oxytetracycline in water is studied by static adsorption experiments.The experimental results showed that the adsorption effect was greatly influenced by the amount of straw and the reaction time,and the removal rate increased with the increase of dosage.When the dosage of straw was 0.06g,the adsorption effect was the best.The removal rate was 96.16%and the saturated adsorption capacity was 16.03mg/g.The adsorption rate of modified corn straw to oxytetracycline was very fast,and the adsorption equilibrium could be reached at 40min.At this time,the removal rate was 97.59%and the adsorption capacity was 16.26mg/g.The adsorption process was less affected by temperature and pH.It could be achieve the best adsorption effect when the temperature was 25 ?,pH=7.According to the result of adsorption experimental data fitting,it can be concluded that the Langmuir adsorption isotherm model can well describe the adsorption behavior of modified corn straw on oxytetracycline in water.The adsorption behavior accords with the pseudo two order kinetics model and is a spontaneous exothermic process.