Preparation Of Pomelo Peel Modified Adsorbent And Its Application In Wastewater Treatment

In our country,the eutrophication of river water pollution have been serious,at the same time,lots of heavy metals had accumulated in water,which caused serious damage to the ecological environment and threatened people's health.Therefore,how to control heavy metal pollution,ammonia pollution effectively have become a global hot spot.At present,adsorption is the most practical method in the water pollution treatment,of which the most of core part is absorbent material.In order to find out an effective way to make use of agricultural biomass waste residue to prepare adsorption material in water treatment,this study based on Xuefeng pomelo peel as raw materials in the Hunan-Guizhou area,carbonization with phosphoric acid to modify pomelo peel carbonaceous biological adsorption material(PP-H3PO4).To enhance the application performance of pomelo peel in water treatment material,further using EDTA-2Na to the esterification modification,preparation for pomelo peel/EDTA-2Na adsorption materials(PP-EDTA),and the series of prepared adsorption materials applied to test process of the simulation wastewater containing Ni(II),Cr(VI)or ammonia nitrogen.The main contents and results of this paper are as follows:1.Studied on preparation of PP-H3PO4.shaping effect and adsorption capacity were comprehensive studied through single factor and orthogonal experiment,the optimum conditions for PP-H3PO4: pomelo powder and pure phosphoric acid mass ratio of 1:1.2,activation temperature of 130 ?,the activation time of 45 min,prepared product of iodine value of 1036.79mg/g.Using Boemh titratio,IR,SEM and TG/DSC analysis techniques to characterize the structures and physic-chemical characters of PP-H3PO4.The results showed that after modification by phosphoric acid,the carbon skeleton of the pomelo peel was changed and had a stronger heat resistance.Moreover,the surface of PP-H3PO4 had a certain oxygen-containing acidic group,and the active functional groups were obviously increased,and the pore structure increased and surface area enlarged.2.Pomelo peel esterification modification experiments.EDTA-2Na esterificationoptimum conditions of preparation of PP-EDTA: pomelo powder and EDTA-2Na mass ratio of 1:1,reaction temperature of 120 C,reaction time of 4h,the dosage of catalyst of 2mL,the PP-EDTA had strong adsorption effect on Ni(II)and the saturated adsorption capacity was up to 140.62mg/g.The characterization analysis showed that there was an esterification reaction of EDTA-2Na in grapefruit powder modification,new carboxyl and amino,-COOH,-OH,-NH2 of the product functional groups increased significantly;after the modification,the roughness in surface and the the hole and raw carbon skeleton structure pomelo peel had changed,but the heat resistance had decreased.3.The sewage treatment experiences of PP-H3PO4 products.The removal ratio increased firstly and then leveled off with the increase of dosage and adsorption time;Ni(II)and ammonia nitrogen of the best treatment pH values were 6 and 8,while the smaller pH was more conducive to the removal of Cr(VI);the optimum treatment time was 90 min;salt concentration increase had little or no effect on PP-H3PO4 on the adsorption of Cr(VI),but attributed to the competitive adsorption of Ni(II)and ammonia nitrogen removal process.By the acid and alkali desorption experiments,the desorption rate of 0.1mol/L HCl solution for Ni2+ was 55%,and the desorption rate of Cr(VI)and ammonia nitrogen by 0.1mol/L NaOH was 85.6% and 52.9% respectively.4.The experiment found that adsorption of pollutants ions PP-EDTA,the adsorption effect of the main factors and the change trends were similar to that of PP-H3PO4,with the increase of the dosage and adsorption time,the removal ratio firstly increased and then leveled off slightly;the best treatment time of Ni(II),Cr(VI)and ammonia nitrogen were 60 min,120min and 60min;the best treatment of ammonia nitrogen pH value was 8,the pH value was smaller,the removal rate of Cr(VI)was higher.The difference was that the removal of Ni(II)by PP-EDTA was almost not affected by the pH value,and the increase of salt concentration had no influence on the adsorption of Cr(VI)and Ni(II),but there was still a competitive adsorption on the removal of ammonia nitrogen.The desorption test results showed that the desorption rate of 0.1mol/L HCl solution for Ni2+ was 77.6%,and the desorption rate of 0.1mol/L NaOH solution for Cr(VI)and ammonia nitrogen was47.5% and 81.3% respectively.Through the comparison of adsorption and desorption rate,the adsorption effect of PP-EDTA on Ni(II)and ammonia nitrogen ion was better.The adsorption and desorption of Cr(VI)by PP-H3PO4 was slightly better than that of PP-EDTA.5.Dynamic study results showed that the adsorption behavior of PP-H3PO4 and PP-EDTA on the contaminants were in line with the pseudo-second-order model;Langmuir and Freundich isothermal adsorption test data showed that the Langmuir isotherm described Ni(II)and Cr(VI)adsorption process meritoriously,but for the removal of ammonia Freundich isotherm fitted better,and higher temperature is conducive to the adsorption of PP-H3PO4 on ammonia nitrogen,lowering the temperature was conducive to the adsorption of PP-EDTA on ammonia nitrogen.The thermodynamic analysis showd that the adsorption process were chemical adsorption and endothermic process.