Adsorption Removal of Environmental Hormones of Dimethyl Phthalate Using Novel Magnetic Adsorbent

Magnetic polyvinyl alcohol adsorbent M-PVAL was employed to remove and concentrate dimethyl phthalate DMP. The M-PVAL was prepared after sequential syntheses of magnetic Fe3O4(M) and polyvinyl acetate (M-PVAC). The saturated magnetizations of M, M-PVAC, and M-PVAL are 57.2, 26.0, and 43.2 emu g−1with superparamagnetism, respectively. The average size of M-PVAL by number is 0.75 μm in micro size. Adsorption experiments include three cases: (1) adjustment of initial pH (pH0) of solution to 5, (2) no adjustment of pH0with value in 6.04–6.64, and (3) adjusted pH0= 7. The corresponding saturated amounts of adsorption of unimolecular layer of Langmuir isotherm are 4.01, 5.21, and 4.22 mg g−1, respectively. Values of heterogeneity factor of Freundlich isotherm are 2.59, 2.19, and 2.59 which are greater than 1, revealing the favorable adsorption of DMP/M-PVAL system. Values of adsorption activation energy per mole of Dubinin-Radushkevich isotherm are, respectively, of low values of 7.04, 6.48, and 7.19 kJ mol−1, indicating the natural occurring of the adsorption process studied. The tiny size of adsorbent makes the adsorption take place easily while its superparamagnetism is beneficial for the separation and recovery of micro adsorbent from liquid by applying magnetic field after completion of adsorption.

Adsorption Kinetics of Lignite Activated Carbon in Treating Coal Gasification Wastewater

Lignite activated carbon was provided through lignite which is treated specially. The adsorption capacity and mechanism of COD from Coal gasification wastewater by lignite activated carbon have been studied.The adsorption capacities of lignite activated carbon at different times were obtained by concentration of COD in the remainder solution. Three simplified kinetic models: pseudo-first-order, pseudo-second-order, intraparticle diffusion equations were adopted to examine the mechanism of the adsorption process. The results showed that the adsorption can be expressed by the pseudo-second-order model. The adsorption balance capacity was obtained as 50.8mg·g-1 (298K), and the adsorption balance capacity decreased with increasing of temperature, which showed that the adsorption process was exothermic. The adsorption activation energy (Ea) was calculated as 5.76kJ·mol-1, and it showed that the adsorption process was Physical adsorption. This study explored new treatment channels for lignite comprehensive utilization..

The Adsorption Behavior of Modified Peanut Shells for Cr (VI)

The adsorption of Cr(VI) by modified peanut shell has been investigated using chemical methods and IR spectrometry. The optimal condition for the adsorption of Cr(VI) by modified peanut shell is at 308 K and pH = 1.0, which gives a static saturated adsorption capacity of 14.15 mg·g-1, an apparent adsorption rate constant of k298 = 2.43 × 10-4 s-1, and an apparent adsorption activation energy of 10.58 kJ·mol-1. The adsorption follows the Langmuir and Freundlich isotherms and the liquid film diffusion is the controlling process of the adsorption. The adsorption thermodynamic parameters are ΔH = 125.58 kJ·mol-1, ΔS = 0.473 9 kJ·mol-1·K-1, ΔG = -17.81– -27.27 kJ·mol-1. Small amount of desorption is observed only at pH > 11. Adsorption mechanism of modified peanut shells for Cr(VI) was both physical adsorption and chemical adsorption of adsorbent "adsorption-oxidation and reduction processes".

Study on the Adsorption Performance of Zn(II) over Bentonite

Bentonite is applied in the simulative waste water containing Zn (II) ions in this paper, and the influences of initial pH value, temperature, adsorption time, Zn (II) concentration on the adsorption performance have been tested, and thermodynamic and kinetic equation are fitted. The results show that Zn (II) adsorption capacity increases firstly and then tends to balance as the pH increases. The higher the temperature is, the better adsorption capacity is. Zn (II) adsorption occurs within 60 minutes. Langmuir equation is used to fit adsorption thermodynamic equation, which indicates that the adsorption can occur spontaneously, and it is an endothermic and entropy increasing process. In addition, a kinetic equation is more suitable for the description of Zn (II) adsorption mechanism, and adsorption activation energy calculated is 6.90 kJ/mol.

Evaluation of the Adsorption of Cr(VI) by Modified Bamboo Shells

The adsorption of Cr(VI) by modified Bamboo shell has been investigated using chemical methods and IR spectrometry. The optimal condition for the adsorption of Cr(VI) by modified Bamboo shell is at 298 K and pH = 1.0, which gives a static saturated adsorption capacity of 12.68 mg·g-1, an apparent adsorption rate constant of k298 = 9.56 × 10-4 s-1, and an apparent adsorption activation energy of 7.38 kJ·mol-1. The adsorption follows the Langmuir and Freundlich isotherms and the liquid film diffusion is the controlling process of the adsorption. The adsorption thermodynamic parameters are ΔH = 66.04 kJ·mol-1, ΔS = 0.2974 kJ·mol-1·K-1, ΔG = −22.58~−28.52 kJ·mol-1. The anions HPO42-, H2PO4- and SO42- have negligible influence on the adsorption capacity. Small amount of desorption is observed only at pH > 11. The adsorption of Cr(VI) by modified bamboo shell is mainly a chemical process.

Adsorption of Zn(II) in Aqueous Solutions by Kaolin

In this paper, adsorption performance of Zn(II) in simulative waste water by kaolin was studied, and the influences of solution initial pH value, temperature, adsorption time, concentration of Zn(II) were tested. Moreover, the thermodynamic parameters and kinetic equation were calculated. The results show that Zn(II) adsorption capacity firstly increases and then decreases as the pH increases, and the higher temperature, the better adsorption capacity. The Zn(II) adsorption occurs mainly within 60 minutes, and then leveling off. The calculations show that linear correlation coefficient (R2) of langmuir equation is better than the freundlich model fitting results, and Zn(II) adsorption can occur spontaneously, is an endothermic and entropy increasing process. In addition, first-order kinetic equation is more suitable for the description of Zn(II) adsorption mechanism, and adsorption activation energy equals 21.51 kJ•mol-1.

Study on the Adsorption of Methylene Blue by Starch-G-Poly(acrylic Acid)

By using grafting reaction, starch-g-poly (acrylic acid) (starch-g-PAA) hydrogel was prepared and used to adsorb methylene blue (MB). Adsorption isotherm and kinetic of the sorption process were studied. Meanwhile, various thermodynamic parameters were calculated. The absorption experimental results demonstrate that the prepared starch-g-PAA is an effective adsorbent for removal of MB from aqueous solution. The adsorption of MB by starch-g-PAA is Freundlich type. Furthermore, the adsorption kinetics analyze demonstrates that the adsorption process follows the pseudo-second-order model, and the adsorption is a multi-step process. Moreover, the calculated thermodynamic parameters indicate the spontaneous and endothermic nature of the adsorption process. The values of adsorption activation energy demonstrate that the adsorption is mainly diffusion-controlled process.