Chemical absorption of carbon dioxide with asymmetrically heated polytetrafluoroethylene membranes.

In this study, the absorption of carbon dioxide using an absorbent composed of 2-amino-2-methyl-L-propanol (AMP) + monoethanolamine (MEA) + piperazine (PZ) in asymmetric and symmetric polytetrafluoroethylene (PTFE) membrane contactors was investigated. Experiments were conducted using various gas flow rates, liquid flow rates, and absorbent blends. CO(2) recovery increased with increasing liquid flow rates. The mean pore size of PTFE membrane reduced via heating treatment. An asymmetric membrane had a better CO(2) recovery than a symmetric membrane. For the asymmetric membrane, placing the smaller pore-size side of the membrane in contact with the liquid phase, reduced the level of wetting of the membrane. The membrane mass transfer coefficient and durability of the PTFE membrane were enhanced by asymmetrically heating.

Adsorption of acid dye from water onto pristine and acid-activated clays in fixed beds.

The adsorption of an acid dye from water onto pristine and HCl-activated montmorillonites in fixed beds was investigated. Experiments were carried out as a function of liquid flow rate, initial dye concentration, and bed height. The adsorption capacity of acid dye onto pristine clay could be largely improved when the clay was activated by HCl. A mass transfer model that involves only two parameters, tau (50% breakthrough time) and kappa (adsorption rate constant), was proposed. This model could satisfactorily describe the measured breakthrough curves of acid dye in fixed beds (standard deviation <6%). It was shown that the value of tau decreased with increasing liquid flow rate. The effect of the type of clay (pristine, acid-activated) on the values of kappa, tau, and adsorption capacity was discussed, and the application potential of acid-activated clay for adsorption removal of acid dye from water was also demonstrated.

Removal of heavy metal ions from aqueous solutions using various low-cost adsorbents.

The removal of single heavy metals Co and Zn from aqueous solutions using various low-cost adsorbents (Fe(2)O(3), Fe(3)O(4), FeS, steel wool, Mg pellets, Cu pellets, Zn pellets, Al pellets, Fe pellets, coal, and GAC) was investigated. Experiments were performed at different solution pH values (1.5-9) and metal concentrations (0.67-333 mg/l). The effect of solution pH on metal adsorption using Fe(2)O(3) and Fe(3)O(4) was significant, but was negligibly small using steel wool, Mg pellets, Fe pellets, and Al pellets over the entire pH range. Steel wool and Mg pellets were the most excellent adsorbents; for example, the removal of Zn and Co from dilute solutions (<35 mg/l) was greater than 94% at an adsorbent dose of 1.7 g/l. A mass transfer model, which involves two parameters tau (50% breakthrough time) and k (proportionality constant), was proposed to describe breakthrough data of Co in the fixed beds packed with steel wool and Mg pellets. The calculated breakthrough curves agreed well with the measured data (standard deviation < 6%). The value of tau decreased with increasing the flow rate. The effects of flow rates on the value of k and adsorption capacity are discussed.