Adsorption Of Dyes And Surfactants In Aqueous Solutions By Chromium-containing Leather Waste

The adsorption behaviors of chromium-containing leather waste to anionic dyes (direct pink 12B, direct orange, acid flavine G and acid ATT), anionic surfactant (sodium dodecylbenzenesulfonate, SDBS), cationic surfactant (dodecyl trimethylammonium bromide, DTB) and non-ionic surfactant (Triton X-100, TX-100) in aqueous solution were investigated. The results indicated that both anionic dyes and anionic surfactant could be significantly adsorbed by this novel adsorbent. The adsorption isotherms of direct pink 12B, direct orange, acid flavine G, acid ATT and SDBS on the adsorbent could be fitted by Langmuir model. Acidic pH value favors the adsorption of the anionic compounds and their adsorption capacities decrease with the increase of pH value. The adsorption capacities of dyes and surfactants increased with the rise of temperature. For example, the biggest adsorption amounts of direct pink 12B, direct orange, acid flavine G, acid ATT and SDBS at 293K were 821mg/L, 467 mg/L, 765 mg/L, 798 mg/L and 389mg/L respectively, when initial concentration of solution was 2000mg/L, and it reached 1396mg/L, 598 mg/L, 837 mg/L, 968 mg/L and 394 mg/L at 313K respectively, which indicates that the mechanism of the adsorption might be chemical adsorption. Meanwhile, bigger ion strength leaded to higher adsorption capacity of SDBS onadsorbent, whilst it is contrary to the adsorption of dyes. The removal extent of anionic dyes and surfactant increases with increasing amount of adsorbent and the value was easy to attaine 95%. For the direct pink 12B, direct orange and acid ATT, they could be completely removed from solution using a proper amount of adsorbent. The adsorption kinetics data could be well described by the pseudo-second-order rate model. The adsorption capacities calculated by the pseudo-second-order rate model were close to those determined by actual measurement. The column adsorption kinetics studies showed that the adsorption column has a high availability for adsorption of anionic dyes and anionic surfactant. For example, when the adsorption column filled with 2.0g chromium-containing leather waste (diameter 11mm, height 280mm) was employed, the breakthrough point of lOOmg/L SDBS solution was at 150 bed volumes. For the direct pink 12B, direct orange, acid flavine G and acid ATT solutions with initial concentration of lOOOmg/L, the breakthrough points were 40, 21, 30 and 35 bed volumes, respectively. Desorption studies showed that only 90% of anionic dyes and SDBS adsorbed on adsorption column could be desorbed by using 0.1mol/LNaHCO3. The method of desorbing dyes and surfactant needs to be further studied.