Absorption Of Styrene On Modified Sepiolite

Styrene belongs to the strong toxic hazardous chemicals, is a typical kind of volatileorganic compounds(VOCs), which is harm to human and organism because of it’s chronictoxicity and carcinogenicity. Sepiolite is low price and a fibrous silicate clay mineral andat low cos. The adsorption of volatile organic compounds(VOCs) is excellent usingmodified sepiolite, the surface area of which is higher than that of the original sepiolite. Inthis study, modified sepiolite was used as adsorbent and the adsorbability to styrene wasdiscussed.In this work, different activated sepiolite method is taken into account, such as treatby hydrothermal method, activate by solution of hydrochloric acid. In addition, thestructure and surface chemical composition of modified activated carbon were studied bymeans of SEM-EDS, FT-IR, TG and so on. The adsorption mechanism of styrene onmodified activated sepiolite was also discussed. And the Temperature ProgrammedDesorption(TPD) method is applied to research the desorption activation energy onmodified sepiolite and untreated sepiolite. The main experimental results and conclusionsare summarized as follows:First, examine the different conditions modified sepiolite surface structure (aperture,the surface impurities) and chemical functional groups (including oxygen acid andalkaline functional group) variations, to analyze adsorption of styrene saturated influenceson amount. The results show that hydrothermal modification method of sepiolite ofstyrene adsorption performance than hydrochloric acid modified sepiolite. The first usehydrothermal treatment, then hydrochloric acid method modification effect is better.Second, through to the sepiolite acidity and hydrothermal modification, its specificsurface area and volume, pore diameter had the very big enhancement, the optimal acidmodified sepiolite specific surface area, pore volume and were59.288m~2/g,0.072cc/g,19.282A; The optimal hydrothermal modification sepiolite86.661m~2/g,0.066cc/g,19.259A.Third, in the best condition modified acid (hydrochloric acid concentration12%,modification time10.5h) static adsorption of saturated adsorption of up to111mg/g, thanthe original sepiolite up by105.56%; Hydrothermal modification modified best bestconditions (modification temperature180℃, the modification time3h) static adsorption of saturated adsorption of up to132mg/g, than the original sepiolite increased by144.44%, the static adsorption ability has been improved a lot.Fourth, in this work, the breakthrough curves of styrene in fixed beds packedseparately with hydrochloric acid-modified sepiolite were determined. And theTemperature Programmed Desorption (TPD) method is applied to research the desorptionactivation energy on modified sepiolite and untreated sepiolite. The results showed that incompared with the original sepiolite, the hydrochloric acid-modified sepiolite had moresurface basic groups, pore volume and higher surface area so that their adsorptioncapacities of styrene were improved. The sepiolite modified with temperature180℃, themodification time3h water heat treatment had more micropore volume and higher surfacearea than the other modified sepiolite, and thus its adsorption capacity of styrene was thehighest. The activation energy for desorption of styrene on the modified is higher than onthe original sepiolite, this show that using hydrochloric acid modified sepiolite canenhance its adsorption of styrene.Fifth, the dynamic adsorption experiment, the concentration of styrene increases, themass transfer impetus become larger, the breakthrough curve become steeper, masstransfer area become shorter, and at the same time in advanced through time. With the riseof temperature, through time are short and the breakthrough curve moved forward,through the adsorption capacities and saturated adsorption declined. The raisingtemperature is not beneficial for adsorption, but in small range of temperature has a littleeffect on adsorption. Desorption activation energy is larger, indicates that the energy foradsorbate desorbed from the adsorbent required larger, whereby the interaction forcesbetween the adsorbent and adsorbate are stronger. TPD curves of styrene in modifiedsepiolite showed a narrow asymmetric peak, belongs to the first-order kinetic equation. Inprocess conditions for the mixture flow25mL/min, adsorption40℃temperature,thereare the maximum desorption activation energy. It can be seen from table4, comparedwith the raw sepiolite, the desorption activation energy of styrene in acid modifiedsepiolite larger.