Preparation Of Diatomite Adsorbent Modified By Organic And Its Adsorption Properties

As a natural mineral clay,diatomaceous earth?De?has abundant reserves,low mining cost,rich and developed porous structure,and large specific surface area.It is often used as an adsorption material to treat printing and dyeing wastewater.However,natural diatomaceous earth has a limited adsorption capacity and is generally negatively charged.On the one hand,this structure determines that diatomaceous earth has a certain adsorption effect on cationic dyes;on the other hand,it is almost no adsorption effect on anionic dyes.Therefore,diatomaceous earth is modified to improve the adsorption capacity of cationic dyes,and make it further suitable for the adsorption treatment of anion and cation mixed dye wastewater.It is very necessary to broaden the application range of diatomite,a cheap adsorption material.In this paper,two adsorbents are prepared for the organic modification of diatomite.First,humic acid?HA?is used to modify diatomite with calcium silicate gel to prepare a humic acid modified diatomite adsorbent?De-HA?.In order to further optimize the modification of diatomite clay,glutaraldehyde was used as a crosslinking agent,and chitosan?CTS?and humic acid were combined to modify diatomite to prepare a diatomite-humic acid/Chitosan amphoteric adsorbent?De-HA/CTS?.SEM,BET,FI-IR,elemental analysis,XPS and zeta potential were used to investigate the effect of organic modification on the microstructure and adsorption properties of diatomite.secondly,the cationic dye methylene blue?MB?was used as the target pollutant to study the adsorption performance and adsorption mechanism of De-HA.Finally,the adsorption performance and adsorption mechanism of De-HA/CTS were studied with cationic dye methylene blue?MB?and anionic dye methyl orange?MO?as the target pollutants;and De-HA/CTS adsorbent tried to treat the actual industrial printing and dyeing wastewater,using UV₂₅₄ to investigate the adsorption effect.The main research contents is as follows:?1?De?De-HA and De-HA/CTS were characterized by SEM?BET?FI-IR?elemental analysis?XPS and zeta potential.The results show that diatomaceous earth has a round cake-like porous structure and can be used as a good carrier for loading organic matter.Compared with diatomaceous earth,the organically modified De-HA and De-HA/CTS have rough and wrinkled surfaces,and the specific surface area and average pore diameter are significantly increased,which is beneficial to the adsorption of macromolecular dyes.The content of C and N in De-HA increased from 0.03%to 3.04%and 0.07%to 0.09%,respectively.and the C element increased significantly;the content of C and N in De-HA/CTS increased from 0.03%to 21.08%,0.07%increased to 2.62%,respectively.And the C and N elements in De-HA/CTS both increased significantly.Combined with FI-IR spectrum and XPS spectrum,it shows that both HA and CTS can be successfully loaded on diatomaceous earth;the-COOH and other groups contained on the surface of De-HA are beneficial to the adsorption of cationic dye MB;the surface of De-HA/CTS contains the-NH-C=O structure that makes De-HA/CTS have certain amphoteric characteristics.The zeta potential analysis shows that the organic modification of diatomite significantly improves its surface electrical properties,which is an important factor in determining its adsorption properties.?2?Humic acid modified diatomaceous earth adsorbent?De-HA?is used to adsorb cationic dye MB.De-HA can efficiently adsorb cationic dye MB,and its removal rate is 95.50%,which is about 20%higher than that of diatomaceous earth.The adsorption comparison experiment of different preparation methods shows that the adsorption effect of calcium silicate gel and HA modification method is the best.p H is one of the important factors affecting the adsorption effect.With the increase of p H,the removal rate of De and De-HA on MB increases,and the adsorption effect of De-HA on MB is higher than that of De.De-HA can separate MB from MB-MO anion and cation mixed dyes,and when the relative concentration of MB in the mixed dye wastewater is not greater than 1,the MB adsorption effect is more obvious.The isotherm adsorption process of De-HA on MB is more in line with the Langmuir model and belongs to the preferential monolayer adsorption.Compared with De,the maximum adsorption capacity of De-HA on MB has increased from 133.33 mg·g^-1 to 263.16 mg·g^-1;The adsorption kinetics process is more in line with the quasi-secondary kinetic model,the adsorption equilibrium time is 2h,and the adsorption process is mainly chemical adsorption.The charge effect between-COOH contained in De-HA and cationic pollutants is the main factor that determines the adsorption characteristics of De-HA.?3?Diatomite-humic acid/chitosan amphoteric adsorbent?De-HA/CTS?is used to adsorb cationic dye MB and anionic dye MO respectively.The experimental results of the dosage showed that with the increase of the adsorbent dosage,the removal rate of MB and MO by De-HA/CTS both increased first and then remained basically unchanged.The p H experiment showed that with the increase of p H,the removal rate of MB by De-HA/CTS gradually increased,and the optimum p H was 11;the removal rate of MO by De-HA/CTS first increased and then decreased,and the optimum p H was 3.De-HA/CTS shows a certain sensitivity to p H and has certain amphoteric characteristics.At p H is 11,-NH-C=O in De-HA/CTS dissociates into-COO-and-NH₂,at p H is 3,-NH-C=O in De-HA/CTS dissociates Into-COOH and-NH₃⁺.By adjusting the p H of wastewater,the purpose of separating cationic dyes or anionic dyes in wastewater can be achieved.The isothermal adsorption process of De-HA/CTS on MB and MO is more in line with the Langmuir model and belongs to the preferential monolayer adsorption.The maximum adsorption capacity of De-HA/CTS for MB and MO is 159.24mg·g^-1 and 316.46 mg·g^-1,respectively;the adsorption kinetics of MB and MO by De-HA/CTS is more in line with the quasi-second-order kinetic model.The adsorption process is mainly chemical adsorption,the equilibrium adsorption time for MB and MO is 4h and 2h,respectively.The charge effect between-NH-C=O contained in De-HA/CTS and pollutants is the main factor that determines the adsorption characteristics of De-HA/CTS.Using De-HA/CTS in industrial printing and dyeing wastewater has a good adsorption effect on both dye and non-dye pollutants in industrial printing and dyeing wastewater.This shows that it is feasible to use De-HA/CTS for advanced treatment of actual printing and dyeing wastewater.