Sumaeth Chavadej

Anionic and cationic surfactant recovery from water using a multistage foam fractionator

Surfactants can be present at low concentrations in effluent wastewater from various industrial operations. Also, the increasing use of surfactant-based separations results in surfactants in water generated by these separations. The surfactant concentration must sometimes be reduced in order to meet environmental standards in discharging these waters to the environment. Also, recovery of the surfactant for reuse is sometimes economical and desirable. Foam fractionation has been shown to be an effective method of removing anionic or cationic surfactants from water in a single stage in previous works. In this study, the recovery of a cationic surfactant (cetylpyridinium chloride, CPC) and an anionic surfactant (sodium dodecylsulfate, SDS) from water by multistage foam fractionation in a bubble-cap trayed column was investigated with one to four stages operated in steady-state mode for surfactant concentrations less than the critical micelle concentration (CMC). In a previous study of a single-stage foam fractionator, CPC was shown to be effectively removed from water, and in agreement with this study. In this study, multiple trays are investigated. Enrichment ratios as high as 120.23 were observed and increased with decreasing superficial air flow rate, increasing foam height of the top tray, increasing feed liquid flow rate, decreasing feed surfactant concentration, and increasing number of stages. The fractional surfactant removal can be as high as 100% and increases with decreasing air flow rate, increasing foam height per tray, increasing feed liquid flow rate, increasing feed surfactant concentration, and increasing number of stages. Scale-up of foam fractionation for recovery or removal of surfactant from water to a multi-tray column was successful.

Purification and concentration of a rhamnolipid biosurfactant produced by Pseudomonas aeruginosa SP4 using foam fractionation

Pseudomonasaeruginosa SP4 was cultivated to produce a rhamnolipid biosurfactant from a nutrient broth with palm oil. The foam fractionation technique in batch mode was used for the recovery of the excreted biosurfactant from the free-cell culture medium. The effects of air flow rate, initial foam height, the pore size of the sintered glass disk, initial liquid volume, and operation time on the process performance were studied. The results showed that the operating conditions were optimized at an air flow rate of 30 ml/min, an initial foam height of 60 cm, a pore size of the sintered glass disk in the range of 160-250 microm (No. 0), an initial liquid volume of 25 ml, and an operation time of 4 h, providing a biosurfactant recovery of 97% and an enrichment ratio of 4. The HPLC results also indicated that the rhamnolipid was concentrated by using the foam fractionation technique.

Color removal of distillery wastewater by ozonation in the absence and presence of immobilized iron oxide catalyst

Ozone is a strong oxidant, which can oxidize both biodegradable and non-biodegradable organics. The main objective of this study was to use iron oxide as a heterogeneous catalyst to enhance the ozone oxidation process. The wastewater used in this study was distillery wastewater, which was diluted 20 times before use. The diluted distillery wastewater was fed continuously in a downflow direction in an ozonation column. The iron oxide catalyst was coated on 10.3mm diameter alumina balls (5.5 m2/g specific surface area) by using Fe(NO3)3 as a precursor. The prepared catalyst was in the form of ferric oxide, and its loading was 0.07%. From the experimental results of both with and without the iron oxide catalyst, an increase in hydraulic retention time resulted in an increase in the treatment efficiencies of both chemical oxygen demand (COD) and color reduction, since the residence time of ozone increased. When the ozone mass flow rate increased, both COD and color reduction increased, resulting from an increase in the hydroxyl radical available in the system. The ozonation system with the iron oxide catalyst gave the highest efficiency in both COD and color removals because the hydroxyl free radical generated from the catalyst is more reactive than the ozone molecule itself.

Solution properties and vesicle formation of rhamnolipid biosurfactants produced by Pseudomonas aeruginosa SP4.

A biosurfactant produced by Pseudomonas aeruginosa strain SP4 was previously reported as a mixture of 11 types of rhamnolipid compounds. Among them, the major component in the biosurfactant was characterized as l-rhamnosyl-3-hydroxydecanoyl-3-hydroxydecanoate, or monorhamnolipid (Rha-C(10)-C(10)). In this present study, solution properties of the biosurfactant were investigated in a phosphate-buffer saline (PBS) solution (pH 7.4) by using surface tension, turbidity, electrical conductivity, and dynamic light scattering (DLS) measurements. It was found that spherical biosurfactant vesicles of various sizes (ranging from 50 to larger than 250 nm) were spontaneously formed at a biosurfactant concentration greater than its critical micelle concentration (CMC), which was 200mg/l. The encapsulation efficiency (E%) of the biosurfactant vesicles was preliminarily studied by using Sudan III, a water-insoluble dye, as a model hydrophobic substance. The obtained results showed that the vesicle formed in the PBS solution at a biosurfactant concentration of 1280 mg/l could entrap about 10% of the initial hydrophobic dye concentration. The effects of salt and alcohol on the vesicle formation of the biosurfactant and its encapsulation efficiency were also observed by using sodium chloride (NaCl) and ethanol (C(2)H(5)OH), respectively. In the presence of either NaCl or C(2)H(5)OH, the vesicle size was reduced from larger than 250 nm to 50-250 nm. The encapsulation efficiency of the biosurfactant vesicle was slightly influenced by the addition of NaCl, but was significantly increased, up to nearly 30%, in the presence of C(2)H(5)OH.

Optimization of separate hydrogen and methane production from cassava wastewater using two-stage upflow anaerobic sludge blanket reactor (UASB) system under thermophilic operation.

The objective of this study was to investigate the separate hydrogen and methane productions from cassava wastewater by using a two-stage upflow anaerobic sludge blanket (UASB) system under thermophilic operation. Recycle ratio of the effluent from methane bioreactor-to-feed flow rate was fixed at 1:1 and pH of hydrogen UASB unit was maintained at 5.5. At optimum COD loading rate of 90 kg/m3 d based on the feed COD load and hydrogen UASB volume, the produced gas from the hydrogen UASB unit mainly contained H2 and CO2 which provided the maximum hydrogen yield (54.22 ml H2/g COD applied) and specific hydrogen production rate (197.17 ml/g MLVSSd). At the same optimum COD loading rate, the produced gas from the methane UASB unit mainly contained CH4 and CO2 without H2 which were also consistent with the maximum methane yield (164.87 ml CH4/g COD applied) and specific methane production rate (356.31 ml CH4/g MLVSSd). The recycling operation minimized the use of NaOH for pH control in hydrogen UASB unit.

Biosurfactant production by Pseudomonas aeruginosa SP4 using sequencing batch reactors: effects of oil loading rate and cycle time.

In this present study, sequencing batch reactors (SBRs) were used for biosurfactant production from Pseudomonasaeruginosa SP4, which was isolated from petroleum-contaminated soil in Thailand. Two identical lab-scale aerobic SBR units were operated at a constant temperature of 37 degrees C, and a mineral medium (MM) with palm oil was used as the culture medium. The effects of oil loading rate (OLR) and cycle time on the biosurfactant production were studied. The results indicated that the optimum conditions for the biosurfactant production were at an OLR of 2 kg/m(3)days and a cycle time of 2 days/cycle, which provided a surface tension reduction of 59%, a chemical oxygen demand (COD) removal of 90%, and an oil removal of 97%. Under the optimum conditions, it was found that the biosurfactant production was maximized at an aeration time of 40 h. These preliminary results suggest that the SBR can potentially be adapted for biosurfactant production, and perhaps further developed, potentially for large-scale biosurfactant production.

Surfactant Recovery from Water Using a Multistage Foam Fractionator: Part I Effects of Air Flow Rate, Foam Height, Feed Flow Rate and Number of Stages

Abstract Surfactants can be present at low concentrations in wastewater from many industries, such as papermaking or detergent manufacture. The surfactant must sometimes be reduced in concentration in order to meet environmental standards before discharging these wastewaters to the environment. Also, recovery of the surfactant for reuse is sometimes economical and desirable. Foam fractionation has been shown to be an effective method of removing anionic and cationic surfactants from water in a single stage in our previous work. In this study, the recovery of a cationic surfactant (cetylpyridinium chloride or CPC) from water by multistage foam fractionation in a bubble‐cap trayed column was investigated with one to four stages operated in steady‐state mode for surfactant concentrations less than or equal to the critical micelle concentration. In comparison with a single‐stage foam fractionator, CPC was found to be removed from water by the multistage foam fractionator much more effectively. Both enrichment ratio and surfactant removal fraction increase with increasing feed flow rate, foam height, and number of stages, but they decrease with increasing CPC feed concentration and air flow rate. This study has demonstrated that the multistage foam fractionator used in this study can achieve almost quantitative removal of the surfactant with high enrichment ratio and short residence time. Multistage foam fractionation is demonstrated to be an extremely effective method of reducing surfactant concentrations from low to even lower concentrations in wastewater.

Use of Poly electrolyte-Enhanced Ultra filtration to Remove Chromate from Water

Abstract Poly electrolyte-enhanced ultra filtration (PEUF) is a process which can be used to remove multivalent ions from water. In PEUF a poly electrolyte of opposite charge to the target ion is added to the water to bind the ion to be removed. The solution is then treated using ultra filtration with membrane pore sizes small enough to reject the polymer and bound ion. In this study, chromate (CrO2 4 −) is removed from water using poly(diallyldimethyl ammonium chloride) with an average molecular weight of 240K as the poly electrolyte. In the absence of other added electrolytes, chromate rejections of up to 99.8% were observed. The presence of added NaCl reduces the chromate rejection substantially. A study of the flux of the system yielded a gel concentration of 0.55 M cationic poly electrolyte. This high gel concentration and high rejection mean that the ultra filtration can produce a concentrated, low-volume waste stream, and a purified stream containing chromate at low concentration.

Removal of trace Cd2+ using continuous multistage ion foam fractionation: part I--The effect of feed SDS/Cd molar ratio.

In this research, a continuous multistage ion foam fractionation column with bubble-cap trays was employed to remove cadmium ions from simulated wastewater having cadmium ions at a low level (10 mg/L). In this study, sodium dodecyl sulfate (SDS) was used to generate the foam. An increase in feed SDS/Cd molar ratio enhanced the removal of Cd. However, the SDS concentration above a certain level resulted in wetter foams, leading to having a high volume of generated foam that lowered both the enrichment ratio and separation factor of the Cd. The SDS recovery tended to increase with increasing feed SDS/Cd molar ratio. The molar ratio of SDS/Cd in foamate was found to be close to the theoretical adsorption molar ratio of 2/1 on the air-water interface of foam when the system was operated at a feed SDS/Cd molar ratio in the range of 2/1-7/1. Ion foam fractionation has been demonstrated in this study to be a promising technique for high heavy metal removal (more than 99%) for a feed having a low heavy metal concentration in the ppm (mg/L) level.

Borane-functionalized silica supports In situ activated heterogeneous zirconocene catalysts for MAO-free ethylene polymerization

Abstract We treated silica with tris(pentafluorophenyl)borane, B(C 6 F 5 ) 3 , to create borane-functionalized support, SiO 2 –B(C 6 F 5 ) 3 which was then used as a support and co-catalyst for the in situ activated dichloro-zirconocene (Cp 2 ZrCl 2 /TIBA) and dimethyl-zirconocene catalyst systems (Cp 2 Zr(CH 3 ) 2 ) for ethylene polymerization. The surface modifications of SiO 2 –B(C 6 F 5 ) 3 was investigated by SEM–EDX, FTIR and XPS to determine the distribution of fluorine and boron atoms on the silica surface as a measure of the presence of B(C 6 F 5 ) 3 and interaction with the siloxane groups of the silica support. Catalytic performances are presented in the form of ethylene consumption rate profiles. The results show that the independent of the time dedicated to the in situ activation of the metallocene, all pre-activated systems showed activity decay. In contrast, the in situ activated systems either showed little or no activity decay. The presence of TIBA was adequate to make an active MAO-free catalyst system. The pre-activated and in situ activated metallocene systems produced polyethylene with slightly different molecular weights (MWs) and molecular weight distribution (MWD). MWDs were quite narrow ∼3. The bulk density of polyethylene product is highest for the in situ activated metallocenes, but there is no difference between the products of dichloro- and dimethyl-zirconocenes. Pre-activated and in situ activated catalysts show no reactor fouling.