| China's northern region as the traditional old industrial base,the development of industry at the same time essential to bring serious pollution problems,water pollution has become a restriction of enterprise development,hinder the national economy is an important factor.Agriculture as an important industry in China,agricultural products and fruit production are very In this paper,discarded agricultural large,the amount of agricultural waste has increased year by year,resulting in a waste of resources.waste peel as a raw material,modified to make biochar material and used to remove iron and manganese ions in water.First,the zinc nitrate solution is fully contacted with the banana peel to form a zinc complex,and then further develop a complex with the o-aminophenol and furfural molecules.Under high temperature with limited-oxygen condition,biochar adsorbents with porous structure are prepared.It can be seen from the analysis of scanning electron microscopy and transmission electron microscopy that the porous structure of the prepared biochar material is obvious and has a lamellar structure of graphene.This kind of biochar with ultra-thin layer structure has a large number of wrinkles and folding structure,which can effectively increase the specific surface area of biochar and increase the adsorption site.The analysis of X-ray diffraction shows that a wide diffraction peak appears at 20 = 10°?20° and 20 = 23°,indicating that the prepared modified biochar material is graphitized due to the large number of porous structures and the presence of surface wrinkles and the degree of crystallization is not high.For the analysis of pore characteristics and specific surface,it can be seen that the modified agricultural waste biochar material is 1597 m2 g'1,Comparable to commodity grade activated carbon 1393 m2· g-1,Much higher than the specific surface area of raw biochar(459 m2·g-1),For the analysis of the infrared spectrum,it can be seen that the stretching vibration of the hydroxyl(O-H)and the(N-H)stretching vibration of the hydroxyl group resulted in a more obvious peak at 3417 cm-1,where C=C,C=O bond stretching vibration absorption peak,and in 1181 cm-1 and 1565-1700 cm-1 are obvious peaks,and the comparison shows that there is a large number of functional groups on the surface of the modified biochar,Hydroxyl(-OH),carboxyl(-COOH),hydrate(H-OH)and carbon-oxygen bond(C-O),and increase the hydrophilicity of the material,which can promote the adsorption of heavy metal ions.The modified biochar was added to the iron ion solution under different pH conditions to study the adsorption of iron ions.The adsorption capacity and the pH value were between 2.0 and 4.0,the adsorption capacities were 138.8 mg·g-1,153.2 mg·g-1 and 164.6 mg·g-1 respectively,and the corresponding removal rate increased from 68.7%to 82.5%.The adsorption capacity was 180 mg·g-1,185.31 mg·g-1 and 187,28 mg·g-1 at pH 6.0?8.0.Study on the adsorption effect of the modified biochar after adding to the iron ion solution at different times shows that the rate of adsorption of iron ions in the period of 0 min?73 min was faster,and it became stable after 180min.The maximum adsorption capacity was 185 mg·g-1 and the adsorption rate was 92.0%.Through the dynamic fitting pseudo first-order kinetic fitting results(qe)cal?K1?R2 were 76.56 mg·g-1,0.01290 g-1 and 0.845 min-1,pseudo two order kinetics fitting results of 192.31 mg g-1,0.00034 min-1 and 0.998,obviously more in line with the pseudo two order kinetics equation.Study on adsorption isotherm of modified biochar at 30?,40? and 50? three different temperatures,and fitting the Langmuir adsorption model and Freundlich adsorption model,the correlation coefficient R2 obtained by fitting the Langmuir equation has reached 0.99,The correlation coefficients of Freundlich adsorption model were 0.68,0.80 and 0.81,respectively,so the process was more in line with the Langmuir adsorption model.The change in the Gibbs free energy(?G)of the modified biochar at three temperature conditions is-13.46,-14.33 and-14.91 kJ · mol-1,and the entropy change(AS)is 76.44J mol-1k-1,enthalpy change(?H)of 8.51 kJ·mol-1 indicates that the reaction is an endothermic reaction and is capable of spontaneous.Adsorption of manganese ions in solution by modified biochar when the pH was 2.0,the removal rate was 41.3%and the adsorption capacity was 66.05 mg·g-1.When the pH was 8.0,the removal rate was 65%and the adsorption capacity reached 102.84 mg·g-1.Study on the adsorption effect of modified biochar into the solution of manganese ion at different time show that when more than 200 minutes,the modified biochar for the solution of manganese ions in the slow phase of adsorption.Through the dynamic fitting pseudo first-order kinetic fitting results(qe)cal?K1?R2 were 116.24 mg·g-1?0.0174 min-1 and 0.610 min-1,pseudo two order kinetics fitting results of 123.64 mg·g-1,0.01847 min-1 and 0.999 obviously more in line with the pseudo two order kinetics equation,The correlation coefficient of Langmuir equation is better than that of Freundlich adsorption model at three different temperatures at 30?,40? and 50?,the change in the Gibbs free energy(AG)of the modified biochar at three temperature conditions is-12.048,-12.61 and-13.173 kJ ·mol-1,and the entropy change(?S)is 56.19 J·mol-1 k-1,enthalpy change(?H)of 3.3 kJ·mol-1 indicates that the reaction is an endothermic reaction and is capable of spontaneous.In this paper,the modified biochar material is modified by the waste banana peel to improve the adsorption performance,and the adsorption rate is high,therefore,can use agricultural waste modified by the preparation of biochar materials to remove iron and manganese in water. |
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