Huan-Ping Chao

Adsorption of copper(II), cadmium(II), nickel(II) and lead(II) from aqueous solution using biosorbents

Three types of agricultural waste, citrus maxima peel (CM), passion fruit shell (PF) and sugarcane bagasse (SB), were used to produce biosorbents for removing the heavy metal ions of copper(II), cadmium(II), nickel(II) and lead(II) from a pH 5.0 solution. The properties of biosorbents were characterized using scanning electron microscopy (SEM), zeta potential analyzer, Fourier transform infrared (FTIR) spectroscopy, elemental analyzer and tests of cation exchange capacity (CEC). The result indicated that the selected biosorbents possess rich carboxyl (COOH) and hydroxyl (OH) groups to produce a complexation with the heavy metals. Moreover, the negative surface charge of the biosorbent might adsorb the metal ions through the ion exchange. All of the adsorption isotherms indicated that L-type characters represented complexation and ion exchanges that were the adsorption mechanisms of biosorbents toward heavy metals. Biosorbents with higher oxygen content might generate high adsorption capacities. The adsorption capacities of CM and PF, estimated from the fitting to the Langmuir isotherm, are similar to those reported by others regarding biosorbents.

Effects of pore structure and surface chemical characteristics on the adsorption of organic vapors on titanate nanotubes

Effects of pore structure and surface chemical characteristics of titanate nanotubes (TNTs) on their adsorptive removal of organic vapors were investigated. TNTs were prepared via a hydrothermal treatment of TiO2 powders in a 10 M NaOH solution at 150xa0°C for 24xa0h, and subsequently washed with HCl aqueous solution of different concentrations. Effects of acid washing process (or the sodium content) on the microstructures and surface chemical characteristics of TNTs were characterized with nitrogen adsorption-desorption isotherms, FTIR, and water vapor adsorption isotherms. For the adsorption experiments, gravimetric techniques were employed to determine the adsorption capacities of TNTs for four organic vapors with similar heats of vaporization (i.e., comparable heats of adsorption) but varying dipole moments and structures, including n-hexane, cyclohexane, toluene, and methyl ethyl ketone (MEK), at isothermal conditions of 20 and 25xa0°C. The experimental data were correlated by well-known vapor phase models including BET and GAB models. Isosteric heats of adsorption were calculated and heat curves were established. Equilibrium isotherms of organic vapors on TNTs were type II, characterizing vapor condensation to form multilayers. The specific surface area (and pore volume) and hydrophilicity of TNTs were the dominating factors for the determination of their organic vapors adsorption capacity. The GAB isotherm equation fitted the experimental data more closely than the BET equation. The heats of adsorption showed that the adsorption of organic vapors on TNTs was primarily due to physical forces and adsorbates with larger polarity might induce a stronger interaction with TNTs.

Activated carbon derived from spherical hydrochar functionalized with triethylenetetramine: synthesis, characterizations, and adsorption application

Abstract This study investigated the adsorption capacities of various contaminants on glucose-derived hydrochar (GH) and glucose-activated carbon (GAC) functionalized with triethylenetetramine (TETA). The two-stage synthesis process consisted of (1) hydrothermal carbonization using various TETA concentrations (1%–5%) to create TETA-functionalized GHs, and (2) chemical activation with NaOH to produce TETA-GACs. The basic properties of the adsorbents were examined using Brunauer-Emmett-Teller (BET) surface area analysis, Fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy. The adsorption characteristics of the GH and GAC samples toward two heavy metal ions (Pb2+ and Cu2+), phenol, methylene green (MG5), and acid red 1 (AR1) were also examined. The results indicated that GAC1% and GH1% exhibited excellent adsorption capacities. Specifically, the maximum adsorption capacities of GAC1% and GH1% reached 370 mg/g and 128 mg/g for Pb2+, 208 mg/g and 84 mg/g for Cu2+, 196 mg/g and 137 mg/g for phenol, 175 mg/g and 67 mg/g for MG5, and 156 mg/g and 21 mg/g for AR1, respectively. In conclusion, amine functionalization on the surface of GHs and GACs efficiently enhances the removal capacities of various contaminants in water.

Increase in volatilization of organic compounds using air sparging through addition in alcohol in a soil-water system

This study developed a novel method to promote the remediation efficiency of air sparging. According to the enhanced-volatilization theory presented in this study, selected alcohols added to groundwater can highly enhance the volatilization amounts of organic compounds with high Henrys law constants. In this study, the target organic compounds consisted of n-hexane, n-heptane, benzene, toluene, 1,1,2-trichloroethane, and tetrachloroethene. n-pentanol, n-hexanol, and n-heptanol were used to examine the changes in the volatilization amounts of organic compounds in the given period. Two types of soils with high and low organic matter were applied to evaluate the transport of organic compounds in the soil-water system. The volatilization amounts of the organic compounds increased with increasing alcohol concentrations. The volatilization amounts of the test organic compounds exhibited a decreasing order: n-heptanol>n-hexanol>n-pentanol. When 10mg/L n-heptanol was added to the system, the maximum volatilization enhancement rate was 18-fold higher than that in distilled water. Samples of soil with high organic matter might reduce the volatilization amounts by a factor of 5-10. In the present study, the optimal removal efficiency for aromatic compounds was approximately 98%.

Removal of cationic and oxyanionic heavy metals from water using hexadecyltrimethylammonium-bromide-modified zeolite

AbstractThe objective of this study was to develop a dual-electronic adsorbent using hexadecyltrimethylammonium (HDTMA)-modified NaY zeolite. HDTMA-modified zeolite (HMZ) possesses a positive charge on the external surface and a negative charge on the micropore surface, and therefore it simultaneously adsorbs cationic (Cu2+, Zn2+, Ni2+, Pb2+, and Cd2+) and oxyanionic (, ) metal ions. The surface properties of NaY zeolite and HMZ were characterized according to scanning electron microscopy and Fourier transform infrared spectroscopy. The specific surface area, the elemental composition, and cation-exchange capacities were also examined. The obtained data were fitted with three types of kinetic adsorption models, pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The amount of test metal ions adsorbed and the absorption mechanisms were illustrated. Moreover, competitive adsorption between cations and oxyanions was discussed. The results demonstrated that the HMZ behaved as a dual-e...