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This study investigated the photocatalytic degradation of chlorophenols using two different types of porphyrin core star block copolymers (P-PSD and P-PD) with irradiation using visible light. Both P-PSD and P-PD catalysts show similar tendencies in the degradation of chlorophenols. Pentachlorophenol degraded faster than other chlorinated phenols (pentachlorophenol > 2,4,6-trichlorophenol > 2,4-dichlorophenol). The removal rate of chlorophenols using P-PSD was higher than the removal rate using P-PD, a difference which could be attributed to the hydrophobicity of P-PSD. The degradation intermediates and by-products of the chlorophenols were also identified. The analysis results revealed that the degradation of highly-chlorinated phenols was more rapid than the degradation of the less-chlorinated phenols, as confirmed by residual chlorinated compound and chloride ions that were released. The newly synthesized P-PSD catalyst is non-toxic to bacteria. For these reasons, the process of photocatalytic degradation using porphyrin core star block copolymers has potential advantages for the degradation of dissolved chlorophenol pollutants in water.

In this study, we performed a conceptual modeling on solute transport based on theoretical stream tube model (STM) with various travel time distributions assuming a pure convective flow through each tube in order to investigate how the lengths and distributions of solute travel time through STM affect the breakthrough curves at the end mixing surface. The conceptual modeling revealed that 1) the shape of breakthrough curve (BTC) at the mixing surface was determined by not only input travel time distributions but also solute injection mode such as sampling time and pulse lengths; 2) the increase of pulse length resulted in the linear increase of the first time moment (mean travel time) and quadratic increase of the second time moment (variance of travel time) leading to more spreading of solute, however, the second time moment was not affected by travel time distributions and 3) for a given input distributions the increase in travel distance resulted in more dispersion with the quadratic increase of travel time variance. This indicates that stream tube model obeying strictly pure convective flow follows the concept of convective-lognormal transport (CLT) model regardless the input travel time distributions.

In this study, a modified adsorbent, alginate complex beads, was prepared and applied to the removal of mixed contaminants from wastewater. The alginate complex beads were generated by the immobilization of powdered activated carbon and synthetic zeolites onto alginate gel beads, which were then dried at 110 °C for 20 h until the diameter had been reduced to 1 mm. This dry technique increased the hardness of the adsorbent to assure its durability and application. The adsorption onto the alginate complex beads of organic and inorganic compounds, as target contaminants, was investigated by performing both equilibrium and kinetic batch experiments. From the adsorption isotherms, according to the Langmuir equation, the alginate complex bead was capable of effectively removing benzene, toluene, zinc and cadmium. From kinetic batch experiments, the removal efficiencies of benzene, toluene, zinc and cadmium were found to be 66.5, 92.4, 74.1 and 76.7%, respectively, for initial solution concentrations of 100 mg L−1. The results indicated that the adsorbent developed in this study has the potential to be a promising material for the removal of mixed pollutants from industrial wastewater or contaminated groundwater.

An effective adsorbent for the removal of heavy metals was manufactured by immobilization of jujube powder. The adsorptions of Cd, Zn and Cu from aqueous solutions by jujube complex beads (Type 1 and Type 2) were studied in a batch adsorption system. The adsorption data were fitted well with the Langmuir isotherm models. The adsorption capacities (β) for Cd, Zn and Cu were 4.23, 2.93 and 3.64 mg/g in Type 1 and 1.24, 0.70 and 1.35 mg/g in Type 2 beads. The removal efficiencies of the Type 2 beads, with a larger unit surface area, were lower than those of the Type 1 due to part of the casein or cyclic AMP being destroyed during the drying process of the Type 1. These values for Type 1 beads were higher than those of all other adsorbents for each heavy metal. A comparison of the kinetic models on the overall adsorption rate showed that the adsorption system was best described by pseudo-first-order kinetics. The removal efficiencies of Cd, Zn and Cu exhibited similar tendencies to those observed in the equilibrium tests. This indicates that the jujube complex beads developed in this study can be used as promising adsorbents for the removal of heavy metals from wastewater.

This study investigated the encapsulation and photocatalysis of chlorophenol compounds in water using porphyrin-(polystyrene-b-2-dimethylaminoethyl acrylate) star polymer. The chloride ions generated during photocatalytic process were identified and quantified. 2,4,6-Trichlorophenol, pentachlorophenol, and 2,4-dichlorophenol were satisfactorily decomposed in the photoreactor using porphyrin-(polystyrene-b-2-dimethylaminoethyl acrylate) star polymer, with removal efficiencies of 2,454, 498, and 760 mg/g of porphyrin-(polystyrene-b-2-dimethylaminoethyl acrylate) star polymer. The half-life times reached around 30 min, with the exception of that for 2,4-dichlorophenol. The star polymer-impregnated porphyrin is a promising photocatalyst for the removal of chlorophenols.

This study assessed the aqueous benzene removal capacity of a polymeric adsorbent, based on an amphiphilic material, in a batch experiment. Two types of polystyrene-block-poly(N-isopropylacrylamide) have structures containing a hydrophobic core and hydrophilic shell. The encapsulation mechanism of benzene by a polymeric adsorbent was investigated, and found to be attributable to the Van der Waals interactions between the benzene aromatic ring and the hydrophobic core of the adsorbent. The equilibrium data were analyzed using the Langmuir and Freundlich adsorption isotherms, and found to be a good fit to both. The maximum adsorption capacity for benzene by the polymeric adsorbent was found to be 194.53 mg/g. The kinetic data followed a pseudo-first-order kinetic model. Polystyrene-block-poly(N-isopropylacrylamide) showed the potential to be an effective adsorbent for application to wastewater treatment.

In the present study, the applications of mesoporous materials based on silica, namely post-synthesized, one-pot synthesized, and pure MCM-41, were investigated for the removal of phosphate from aqueous solution. The mesostructures were confirmed by X-ray diffraction, Brunauer–Emmett–Teller, Fourier transform spectroscopy, and transmission electron microscopy. The absorptions of phosphate by the mesoporous adsorbents were examined, with different adsorption models used to describe the equilibrium and kinetic data. The maximum adsorption capacities of the mesostructure adsorbents were found to be 45.162, 40.806, and 31.123 mg g–1 for the post-synthesized, one-pot synthesized, and pure MCM-41, respectively. The kinetic data showed that the adsorptions of phosphate onto the post-synthesized and pure MCM-41 followed the pseudo-first-order kinetic model, whereas the one-pot synthesized adsorbent was described by the pseudo-second-order model.

Phosphorous contaminated in the effluent from sewage treatment plants can cause the eutrophication in surface water bodies. In this study, a powder of titanium oxysulfate-sulfuric acid made of ion-exchange materials was immobilized in an alginate gel and this material was examined to evaluate its phosphorous removal efficiency. Equilibrium and kinetic studies were carried out to quantify the adsorption capacity and time dependent removal rate of phosphorous. Adsorption isotherms and kinetic parameters were obtained for the entrapped titanium beads with three different methods. Equilibrium data were analyzed using Langmuir adsorption isotherm model and found to be well fitted to the model. The maximum adsorption capacity for phosphorous by the titanium bead synthesized with the solution method was 92.26 mg/g. Kinetic data followed a pseudo-second-order kinetic model. Due to the low production cost and high adsorption capacity, the titanium bead synthesized by the solution method has a potential to be utilized for the cost-effective removal of phosphorous from wastewater.

Biodegradation of organic compounds during transport in aquifer systems has become an important issue in applying bioaugmentation to a target area. In this study, we conducted a set of laboratory column experiments for various patterns of solutes, that is, KCl only, toluene only, toluene and bacterium Pseudomonas putida, to investigate how the processes of sorption, biodegradation, and bacteria affect the fate of toluene during transport through quartz sand. The column experiments revealed that (i) sorption of toluene onto sand occurred irreversibly with a mass loss of 35% without any retardation, (ii) biodegradation also occurred but to a lesser extent (∼21%) than the irreversible sorption, and (iii) for the case of toluene and bacterium, a rather long tailing was present in the effluent concentraion curves of bacterium and toluene. The tailing of bacterial curve can be explained by the secondary energy minimum of DLVO theory. The tailing of toluene curve was attributed to the sorption of toluene onto bacterial cells during transport which was evidenced by the separate biosorption test. This implies that sorption does not affect directly the microbial activity, and the bacterium Pseudomonas putida can impact toluene transport positively (mass loss via biodegradation) as well as negatively (mass added via enhancement) upon simultaneous introduction into the aquifer. These results would provide valuable information on the design of bioaugmentation scheme for bioremediation of groundwater contaminated with BTEX compounds. © 2011 American Institute of Chemical Engineers Environ Prog, 2011

This study investigates the possibility of monoaromatic compounds benzene and toluene adsorption onto alginate gel (AG–AC) beads with impregnated activated carbon and their regeneration possibility using ultrasound method. Kinetic adsorption tests showed that the AG–AC beads were capable of removing the organic compounds from either individual or mixed compound solutions. Removal ratio of the AG–AC beads was as high as that of free PAC powder for benzene and toluene. The removal was more efficient for toluene (97%) than for benzene (75%), and slightly decreased by 7% and 5% for toluene and benzene respectively even after 5 times regeneration. This indicates that the regeneration method utilizing ultrasound is very efficient for desorption of benzene and toluene from the AG–AC beads developed in this study.

Mesoporous iron oxide, particularly amine-functionalized FeO(x) and FeO(x), was investigated for the removal of toxic heavy metal anions of arsenic and chromium from an aqueous solution. As a control experiment for these toxic compounds, adsorption tests were also performed on Fe3O4 as their counterpart bulk chemical. The mesostructures were confirmed by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and transmission electron microscopy (TEM). In addition, we prepared stock suspensions of meso-FeO(x), amine-functionalized meso-FeO(x) and Fe3O4 particles, and compared their acute toxicity against Daphnia magna. The 24 h-EC50 values of the amine-functionalized meso-FeO(x), meso-FeO(x) and Fe particle suspensions used in this study were 1682, 2549 and 95 mg/L, respectively. Organism toxicity caused by spills of adsorbents can be negated when the amine-functionalized meso-FeO(x), up to 1500 mg/L, is used as the adsorbent for heavy metal treatment. The adsorption of arsenic and chromium by the three adsorbents were examined, and different adsorption models were used to describe the equilibrium and kinetic data. The amine-functionalized meso-FeO(x) adsorbent was found to give the maximum adsorption capacities for arsenic and chromium (33.51 and 25.05 mg/g, respectively). This research gives promising results for the application of modified meso-FeO(x) as an adsorbent of toxic heavy metal anions from aqueous solutions.

We proposed a new method from which kinetic sorption parameters can be estimated using aqueous phase concentration versus time data commonly available from adsorption tests. The method relies on the analytical solution that was solved for two-site reversible sorption kinetics based on mass conservation law for solute in a batch reaction system. In order to validate the method, model parameters were compared with those of three-stage kinetic models available in the literature. It was revealed that model parameters of the two-site kinetics could accurately be estimated as much as other model parameters. Advantage of the new method is acquisition of additional parameter, distribution or partitioning coefficient ( K d ) frequently used in the analysis of chemical transfer in the solid–liquid interface.

We investigated the effects of substrate interactions on the degradation of toluene and methyl tert-butyl ether (MTBE) by Pseudomonas putida during transport through quartz sand because of the coexistence of toluene and MTBE in aquifer systems. A laboratory test was conducted for a pulse injection of a toluene and/or MTBE solution with and without bacteria into a saturated sand column. We found that the effect of toluene on MTBE was negative because the mass recovery of MTBE increased by 30 % when toluene was added, whereas the effect of MTBE on toluene degradation was positive because the mass recovery of toluene decreased by 7 %. These results were comparable with those of a previous batch study on substrate interactions which reported that toluene can be more negative than MTBE at concentrations higher than 25 mg/L. This finding indicates that substrate interaction is also an important mechanism, controlling the fate of contaminants during transport through aquifer systems. In addition, bacteria-facilitated transport was also observed for both substrates. Therefore, for an efficient bioremediation scheme, care should be taken for substrate interaction as well as for bacteria-facilitated transport in porous media.

In this study, we investigated the relationship between cell counting units and biomass forPseudomonas aeruginosa since microbial parameters often need to be defined as mass rather than colony forming unit (CFU) or optical density (OD) which is easily measurable using plate counting method or spectrophotometer especially for any attempt in modeling of contaminant transport and biodegradation in aquifer systems. Results showed that 1.0 OD corresponded to 2.04 × 108 CFU/ml and 2.085 mg/ml with well defined linear relationships of Y (CFU/ml) = 2.0 × 108 X (OD600) + 4.0 × 106 and Y (mg/ml) =2.0087 × (OD600) + 0.0764. Key words: Cell counting unit, colony forming unit, optical density, Pseudomonas aeruginosa.