Displaying publications 1 - 20 of 898 in total

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  1. Tiong KH, Yiap BC, Tan EL, Ismail R, Ong CE
    Xenobiotica, 2010 Jul;40(7):458-66.
    PMID: 20402563 DOI: 10.3109/00498251003786749
    1. The effect of flavonoids on coumarin 7-hydroxylation, an activity marker of an important human liver cytochrome P450 isoform, cytochrome P450 2A6 (CYP2A6), was investigated in this study. 2. Coumarin 7-hydroxylase activity was measured fluorometrically in reaction mixtures containing cDNA-expressed CYP2A6, nicotinamide adenine dinucleotide phosphate generating system and 10 uM coumarin, at various concentrations of flavonoids. 3. Among the 23 compounds tested, most of the active members were from flavonol group of hydroxylated flavonoids, with myricetin being the most potent inhibitor followed by quercetin, galangin, and kaempferol. 4. Further exploration of the inhibition mechanism of these compounds revealed that myricetin, galangin, and kaempferol exhibited mixed-type of inhibition pattern while quercetin was observed to exhibit competitive mode of inhibition. 5. Structure-function analyses revealed that degree of inhibition was closely related to the number and location of hydroxyl groups, glycosylation of the free hydroxyl groups, degree of saturation of the flavane nucleus as well as the presence of the alkoxylated function.
    Matched MeSH terms: Kinetics
  2. Ahmad SA, Shamaan NA, Arif NM, Koon GB, Shukor MY, Syed MA
    World J Microbiol Biotechnol, 2012 Jan;28(1):347-52.
    PMID: 22806810 DOI: 10.1007/s11274-011-0826-z
    A locally isolated Acinetobacter sp. Strain AQ5NOL 1 was encapsulated in gellan gum and its ability to degrade phenol was compared with the free cells. Optimal phenol degradation was achieved at gellan gum concentration of 0.75% (w/v), bead size of 3 mm diameter (estimated surface area of 28.26 mm(2)) and bead number of 300 per 100 ml medium. At phenol concentration of 100 mg l(-1), both free and immobilized bacteria exhibited similar rates of phenol degradation but at higher phenol concentrations, the immobilized bacteria exhibited a higher rate of degradation of phenol. The immobilized cells completely degrade phenol within 108, 216 and 240 h at 1,100, 1,500 and 1,900 mg l(-1) phenol, respectively, whereas free cells took 240 h to completely degrade phenol at 1,100 mg l(-1). However, the free cells were unable to completely degrade phenol at higher concentrations. Overall, the rates of phenol degradation by both immobilized and free bacteria decreased gradually as the phenol concentration was increased. The immobilized cells showed no loss in phenol degrading activity after being used repeatedly for 45 cycles of 18 h cycle. However, phenol degrading activity of the immobilized bacteria experienced 10 and 38% losses after the 46 and 47th cycles, respectively. The study has shown an increased efficiency of phenol degradation when the cells are encapsulated in gellan gum.
    Matched MeSH terms: Kinetics
  3. Din MF, Ujang Z, van Loosdrecht MC, Ahmad A, Sairan MF
    Water Sci Technol, 2006;53(6):15-20.
    PMID: 16749434
    The process for the production of biodegradable plastic material (polyhydroxyalkanoates, PHAs) from microbial cells by mixed-bacterial cultivation using readily available waste (renewable resources) is the main consideration nowadays. These observations have shown impressive results typically under high carbon fraction, COD/N and COD/P (usually described as nutrient-limiting conditions) and warmest temperature (moderate condition). Therefore, the aim of this work is predominantly to select mixed cultures under high storage responded by cultivation on a substrate - non limited in a single batch reactor with shortest period for feeding and to characterize their storage response by using specific and kinetics determination. In that case, the selected-fixed temperature is 30 degrees C to establish tropical conditions. During the accumulated steady-state period, the cell growth was inhibited by high PHA content within the cells because of the carbon reserve consumption. From the experiments, there is no doubt about the PHA accumulation even at high carbon fraction ratio. Apparently, the best accumulation occurred at carbon fraction, 160 +/- 7.97 g COD/g N (PHAmean, = 44.54% of dried cells). Unfortunately, the highest PHA productivity was achieved at the high carbon fraction, 560 +/- 1.62 g COD/g N (0.152 +/- 0.17 g/l. min). Overall results showed that with high carbon fraction induced to the cultivation, the PO4 and NO3 can remove up to 20% in single cultivation.
    Matched MeSH terms: Kinetics
  4. Anisuzzaman SM, Joseph CG, Krishnaiah D, Bono A, Ooi LC
    Water Sci Technol, 2015;72(6):896-907.
    PMID: 26360749 DOI: 10.2166/wst.2015.247
    In this study, durian (Durio zibethinus Murray) skin was examined for its ability to remove methylene blue (MB) dye from simulated textile wastewater. Adsorption equilibrium and kinetics of MB removal from aqueous solutions at different parametric conditions such as different initial concentrations (2-10 mg/L), biosorbent dosages (0.3-0.7 g) and pH solution (4-9) onto durian skin were studied using batch adsorption. The amount of MB adsorbed increased from 3.45 to 17.31 mg/g with the increase in initial concentration of MB dye; whereas biosorbent dosage increased from 1.08 to 2.47 mg/g. Maximum dye adsorption capacity of the durian skin was found to increase from 3.78 to 6.40 mg/g, with increasing solution pH. Equilibrium isotherm data were analyzed according to Langmuir and Freundlich isotherm models. The sorption equilibrium was best described by the Freundlich isotherm model with maximum adsorption capacity of 7.23 mg/g and this was due to the heterogeneous nature of the durian skin surface. Kinetic studies indicated that the sorption of MB dye tended to follow the pseudo second-order kinetic model with promising correlation of 0.9836 < R(2) < 0.9918.
    Matched MeSH terms: Kinetics
  5. Salim MR, Othman F, Imtiaj Ali M, Patterson J, Hardy T
    Water Sci Technol, 2002;46(9):339-46.
    PMID: 12448487
    Several types of water treatment technologies including adsorption are now being used to treat polluted water. In this paper the removal of phenol by adsorption will be discussed. Activated carbons are successfully applied for purification of potable water and the removal of organic pollutants in wastwater. This paper is concerned with a low cost approach to treating waste water that is significant especially for those countries where oil palm is an available agricultural product like Malaysia, Ivory Coast, Nigeria, Thailand, Papua New Guinea. In the coastal region coconut is an available agricultural product and activated carbon prepared using coconut shell is also an economical method of water treatment. The materials used in this study were Commercial Activated Carbon (CAC), prepared from coconut shell and Modified Oil Palm Shell (MOPAS) of 1 to 2 mm diameters. The surface area of CAC and MOPAS was 38.5 m2/g and 38.2 m2/g respectively and the iodine number was determined as 674 and 454 for CAC and MOPAS, respectively. From the study the result shows above 70% removal efficiency for 5 mg/L and 40% removal efficiency for 20 mg/L of phenol solution. The performance efficiency will be discussed based on batch test, following Freundlich adsorption isotherm. The results indicate that CAC exhibits a higher adsorptive capacity (Kf of 0.079) as compared to MOPAS (Kf of 0.048). Hence a better removal efficiency for CAC at lower concentration of phenol. Results from column tests show a better adsorptive capacity for CAC (2.73) as compared to MOPAS (2.48).
    Matched MeSH terms: Kinetics
  6. Idris A, Yen OB, Hamid MH, Baki AM
    Water Sci Technol, 2002;46(9):279-86.
    PMID: 12448479
    A sludge lagoon has been adopted as a simple and cost effective method for dewatering of sludge. The processes occurring in a sludge lagoon include thickening, dewatering, storage and stabilization; all happening simultaneously. The objective of this study is to determine the dewatering and drying rates at pilot-scale which occur in a lagoon having different design configurations. Two types of sludge lagoons with different initial sludge depth (0.75 m and 0.375 m) were investigated to measure the drying behavior and drying efficiency. The first design is a sludge lagoon with a clay bottom where the dewatering mechanisms are decanting supernatant and evaporation. The second design is a sludge lagoon installed with a sand and underdrains system, where the dewatering mechanisms are filtration or draining and evaporation. Sludge drying kinetic models with high fitness were plotted to describe the sludge drying behavior. Drying of sludge in a sludge lagoon with a clay bottom can best be described by an exponential function. Whereas, drying of sludge in a sludge lagoon with sand and underdrains system followed a logarithmic function. A lagoon designed with sand and underdrains system and having shallower sludge depth was the most efficient. The reduction in volatile solids was lower than 4% during the study period. The drying process proceeded with an increase in dryness and decline in pH value.
    Matched MeSH terms: Kinetics
  7. Abdul-Talib S, Hvitved-Jacobsen T, Vollertsen J, Ujang Z
    Water Sci Technol, 2002;46(9):185-92.
    PMID: 12448468
    A significant breakthrough and progress have been made in the study of the kinetics of microbial transformation in sewers under aerobic and under changing aerobic/anaerobic conditions. Fundamental knowledge on anoxic kinetics of wastewater is still lacking, so it is not now possible to apply an integrated approach to municipal wastewater treatment incorporating sewer networks as a bio-chemical reactor. This paper presents the results of studies on determining half saturation constants for nitrate, KNO3, and nitrite, KNO2, in raw wastewater. The average values of KNO3 and KNO2, determined from experiments conducted on 7 different wastewater samples were found to be 0.76 gNO3-N/m3 and 0.33 gNO2-N/m3 respectively.
    Matched MeSH terms: Kinetics
  8. Abdul-Talib S, Hvitved-Jacobsen T, Vollertsen J, Ujang Z
    Water Sci Technol, 2002;45(3):53-60.
    PMID: 11902481
    The sewer is an integral part of the urban wastewater system: the sewer, the wastewater treatment plant and the local receiving waters. The sewer is a reactor for microbial changes of the wastewater during transport, affecting the quality of the wastewater and thereby the successive treatment processes or receiving water impacts during combined sewer overflows. This paper presents the results of studies on anoxic processes, namely denitrification, in the bulk water phase of wastewater as it occurs in sewers. Experiments conducted on 12 different wastewater samples have shown that the denitrification process in the bulk wastewater can be simplified by the reduction of nitrate to nitrogen with significant accumulation of nitrite in the water phase. Utilization of nitrate was observed not to be limited by nitrate for concentrations above 5 gNO3-N/m3. The denitrification rates, under conditions of excess substrate and electron acceptor, were found to be in the range of 0.8-2.0 g NO3-N/(m3h). A discussion on the interaction of the sewer processes and the effects on a downstream located wastewater treatment plant (WWTP) is provided.
    Matched MeSH terms: Kinetics
  9. Abdul-Rahman R, Tsuno H, Zainol N
    Water Sci Technol, 2002;45(12):197-204.
    PMID: 12201103
    Elevated levels of nutrients in agroindustry wastewaters, and higher reliance on chlorination pose health threats due to formation of chlorinated organics as well as increased chlorination costs. Removals of ammonium and nitrate compounds were studied using activated carbon from palm shells, as adsorbent and support media. Experiments were carried out at several loadings, F:M from 0.31 to 0.58, and hydraulic residence times (HRT) of 24 h, 12 h and 8 h. Results show that the wastewater treatment process achieved removals of over 90% for COD and 62% for Total-N. Studies on removals from river water were carried out in sequencing batch reactor (SBR) and activated carbon biofilm (ACB) reactor. Removals achieved by the SBR adsorption-biodegradation combination were 67.0% for COD, 58.8% for NH3-N and 25.5% for NO3-N while for adsorption alone the removals were only 37.0% for COD, 35.2% for NH3-N and 13.8% for NO3-N. In the ACB reactor, at HRT of 1.5 to 6 h, removals ranged from 12.5 to 100% for COD, 16.7 to 100% for NO3-N and 13.5 to 100% for NH3-N. Significant decrease in removals was shown at lower HRT. The studies have shown that substantial removals of COD, NO3-N and NH3-N from both wastewater and river water may be achieved via adsorption-biodegradation by biofilm on activated carbon processes.
    Matched MeSH terms: Kinetics
  10. Bardhan M, Novera TM, Tabassum M, Islam MA, Jawad AH, Islam MA
    Water Sci Technol, 2020 Nov;82(9):1932-1949.
    PMID: 33201856 DOI: 10.2166/wst.2020.451
    In this study, activated carbon (AC) was prepared from agro-waste betel nut husks (BNH) through the chemical activation method. Different characterization techniques described the physicochemical nature of betel nut husks activated carbon (BNH-AC) through Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), and pH point of zero charge. Later, the produced AC was used for methylene blue (MB) adsorption via numerous batch experimental parameters: initial concentrations of MB dye (25-250 mg/L), contact time (0.5-24 hours) and initial pH (2-12). Dye adsorption isotherms were also assessed at three temperatures where the maximum adsorption capacity (381.6 mg/g) was found at 30 °C. The adsorption equilibrium data were best suited to the non-linear form of the Freundlich isotherm model. Additionally, non-linear pseudo-second-order kinetic model was better fitted with the experimental value as well. Steady motion of solute particles from the boundary layer to the BNH-AC's surface was the possible reaction dynamics concerning MB adsorption. Thermodynamic study revealed that the adsorption process was spontaneous and exothermic in nature. Saline water emerged as an efficient eluent for the desorption of adsorbed dye on AC. Therefore, the BNH-AC is a very promising and cost-effective adsorbent for MB dye treatment and has high adsorption capacity.
    Matched MeSH terms: Kinetics
  11. Rzig B, Guesmi F, Sillanpää M, Hamrouni B
    Water Sci Technol, 2021 Aug;84(3):552-575.
    PMID: 34388119 DOI: 10.2166/wst.2021.233
    In this study, a response surface methodology (RSM) approach using central composite design (CCD) was investigated to develop a mathematical model and to optimize the effects of pH, adsorbent amount and temperature related to the hexavalent chromium removal by biosorption on peanut shells (PSh). The highest removal percentage of 30.28% was found by the predicted model under the optimum conditions (pH of 2.11, 0.73 g of PSh and 37.2 °C) for a 100 mg/L initial Cr(VI) concentration, which was very near to the experimental value (29.92%). The PSh was characterized by SEM, EDX, FTIR, BET, XRD analyses. Moreover, a Langmuir isotherm fitted well (R2 = 0.992) with the experimental data, and the maximum adsorption capacity was discovered to be 2.48 and 3.49 mg/g respectively at 25 and 45 °C. Kinetic data were well foreseen by pseudo second order. Thermodynamic study depicted that biosorption of Cr(VI) onto PSh was spontaneous and endothermic. Regeneration of the PSh using NaOH showed a loss <5% in the Cr(VI) removal efficiency up to three recycle runs. In summary, the Cr(VI) removal onto economic, sensitive and selective biosorbent (PSh) was optimized using CCD to study biosorption behaviors.
    Matched MeSH terms: Kinetics
  12. Soo JW, Abdullah LC, Jamil SNAM, Adeyi AA
    Water Sci Technol, 2021 Jul;84(1):237-250.
    PMID: 34280167 DOI: 10.2166/wst.2021.204
    In this paper, the adsorptive performance of synthesized thiourea (TU) modified poly(acrylonitrile-co-acrylic acid) (TU-P(AN-co-AA)) polymeric adsorbent for capturing p-nitrophenol (PNP) from aqueous solution was investigated. TU-P(AN-co-AA) was synthesized via the redox polymerization method with acrylonitrile (AN) and acrylic acid (AA) as the monomers, then modified chemically with thiourea (TU). Characterization analysis with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), elemental microanalysis for CHNS, zeta potential measurement, Brunauer-Emmett-Teller (BET) surface analysis and thermal analyses were carried out to determine the morphology and physico-chemical properties of the synthesized polymer. The characterization results indicated successful surface modification of polymer with TU. The performance of TU-P(AN-co-AA) for the removal of PNP was investigated under various experimental parameters (adsorbent dosage, initial adsorbate concentration, contact time and temperature). The results demonstrated that the Freundlich isotherm model and pseudo-second-order kinetic model best described the equilibrium and kinetic data, respectively. Thermodynamic studies showed that the uptake of PNP by TU-P(AN-co-AA) was spontaneous and exothermic in nature. The results of the regeneration studies suggested that the TU-P(AN-co-AA) polymer is a reusable adsorbent with great potential for removing PNP from wastewater.
    Matched MeSH terms: Kinetics
  13. Alayan HM, Alsaadi MA, Das R, Abo-Hamad A, Ibrahim RK, AlOmar MK, et al.
    Water Sci Technol, 2018 Mar;77(5-6):1714-1723.
    PMID: 29595174 DOI: 10.2166/wst.2018.057
    In this study, carbon species were grown on the surface of Ni-impregnated powder activated carbon to form a novel hybrid carbon nanomaterial by chemical vapor deposition. The carbon nanomaterial was obtained by the precipitation of the methane elemental carbon atoms on the surface of the Ni catalyst. The physiochemical properties of the hybrid material were characterized to illustrate the successful growth of carbon species on the carbon substrate. The response surface methodology was used for the evaluation of adsorption parameters effect such as pH, adsorbent dose and contact time on the percentage removal of MB dye from aqueous solution. The optimum conditions were found to be pH = 11, adsorbent dose = 15 mg and contact time of 120 min. The material we prepared showed excellent removal efficiency of 96% for initial MB concentration of 50 mg/L. The adsorption of MB was described accurately by the pseudo-second-order model with R2 of 0.998 and qe of 163.93 (mg/g). The adsorption system showed the best agreement with Langmuir model with R2 of 0.989 and maximum adsorption capacity (Qm) of 250 mg/g.
    Matched MeSH terms: Kinetics
  14. Zhi LL, Zaini MA
    Water Sci Technol, 2017 02;75(3-4):864-880.
    PMID: 28234287 DOI: 10.2166/wst.2016.568
    This work was aimed to evaluate the feasibility of castor bean residue based activated carbons prepared through metals chloride activation. The activated carbons were characterized for textural properties and surface chemistry, and the adsorption data of rhodamine B were established to investigate the removal performance. Zinc chloride-activated carbon with specific surface area of 395 m(2)/g displayed a higher adsorption capacity of 175 mg/g. Magnesium chloride and iron(III) chloride are less toxic and promising agents for composite chemical activation. The adsorption data obeyed Langmuir isotherm and pseudo-second-order kinetics model. The rate-limiting step in the adsorption of rhodamine B is film diffusion. The positive values of enthalpy and entropy indicate that the adsorption is endothermic and spontaneous at high temperature.
    Matched MeSH terms: Kinetics
  15. How SW, Sin JH, Wong SYY, Lim PB, Mohd Aris A, Ngoh GC, et al.
    Water Sci Technol, 2020 Jan;81(1):71-80.
    PMID: 32293590 DOI: 10.2166/wst.2020.077
    Many developing countries, mostly situated in the tropical region, have incorporated a biological nitrogen removal process into their wastewater treatment plants (WWTPs). Existing wastewater characteristic data suggested that the soluble chemical oxygen demand (COD) in tropical wastewater is not sufficient for denitrification. Warm wastewater temperature (30 °C) in the tropical region may accelerate the hydrolysis of particulate settleable solids (PSS) to provide slowly-biodegradable COD (sbCOD) for denitrification. This study aimed to characterize the different fractions of COD in several sources of low COD-to-nitrogen (COD/N) tropical wastewater. We characterized the wastewater samples from six WWTPs in Malaysia for 22 months. We determined the fractions of COD in the wastewater by nitrate uptake rate experiments. The PSS hydrolysis kinetic coefficients were determined at tropical temperature using an oxygen uptake rate experiment. The wastewater samples were low in readily-biodegradable COD (rbCOD), which made up 3-40% of total COD (TCOD). Most of the biodegradable organics were in the form of sbCOD (15-60% of TCOD), which was sufficient for complete denitrification. The PSS hydrolysis rate was two times higher than that at 20 °C. The high PSS hydrolysis rate may provide sufficient sbCOD to achieve effective biological nitrogen removal at WWTPs in the tropical region.
    Matched MeSH terms: Kinetics
  16. Song J, Cha L, Sillanpää M, Sainio T
    Water Sci Technol, 2023 Apr;87(7):1672-1685.
    PMID: 37051790 DOI: 10.2166/wst.2023.083
    Excessive phosphorus causes eutrophication problems. The adsorptive removal of phosphate is prevalent and practical in large-scale applications, such as column adsorption. A metal organic framework (MOF)-enhanced layered double hydroxide (LDH) adsorbent material was developed and studied for batch adsorption and then combined with polyacrylonitrile (PAN) to form MOF/LDH/PAN composite beads working as a functional material for columns. Scanning electron microscopy (SEM) images showed the well-dispersed adsorbent powder in porous composite beads. The Fowler-Guggenheim isotherm model described the phosphate adsorption behavior of the MOF/LDH powder with a maximum capacity of 74.96 mg P/g. Mass transfer in the composite beads was successfully described with the Fickian diffusion model. The composite-packed fixed bed treated 37.95 BVs of the influent (55.51 mg P/L phosphate solution) and achieved an uptake of 18.92 mg P/g, with a removal efficiency of 96.42%, before the breakthrough point in the column study. The phosphate-loaded composite bed was regenerated with 0.1 M NaOH to 70% efficiency within 30 BVs. The polymer composite can be considered a practical solution for adsorption-based water treatment applications in tank and column processes where powder adsorbents cannot be applied.
    Matched MeSH terms: Kinetics
  17. Chong MF, Lee KP, Chieng HJ, Syazwani Binti Ramli II
    Water Res, 2009 Jul;43(13):3326-34.
    PMID: 19487007 DOI: 10.1016/j.watres.2009.04.044
    Boron is extensively used in the ceramic industry for enhancing mechanical strength of the tiles. The discharge of boron containing wastewater to the environment causes severe pollution problems. Boron is also dangerous for human consumption and causes organisms' reproductive impediments if the safe intake level is exceeded. Current methods to remove boron include ion-exchange, membrane filtration, precipitation-coagulation, biological and chemical treatment. These methods are costly to remove boron from the wastewater and hence infeasible for industrial wastewater treatment. In the present research, adsorption-flocculation mechanism is proposed for boron removal from ceramic wastewater by using Palm Oil Mill Boiler (POMB) bottom ash and long chain polymer or flocculant. Ceramic wastewater is turbid and milky in color which contains 15 mg/L of boron and 2000 mg/L of suspended solids. The optimum operating conditions for boron adsorption on POMB bottom ash and flocculation using polymer were investigated in the present research. Adsorption isotherm of boron on bottom ash was also investigated to evaluate the adsorption capacity. Adsorption isotherm modeling was conducted based on Langmuir and Freundlich isotherms. The results show that coarse POMB bottom ash with particle size larger than 2 mm is a suitable adsorbent where boron is removed up to 80% under the optimum conditions (pH=8.0, dosage=40 g bottom ash/300 ml wastewater, residence time=1h). The results also show that KP 1200 B cationic polymer is effective in flocculating the suspended solids while AP 120 C anionic polymer is effective in flocculating the bottom ash. The combined cationic and anionic polymers are able to clarify the ceramic wastewater under the optimum conditions (dosage of KP 1200 B cationic polymer=100 mg/L, dosage of AP 120 C anionic polymer=50 mg/L, mixing speed=200 rpm). Under the optimum operating conditions, the boron and suspended solids concentration of the treated wastewater were reduced to 3 mg/L and 5 mg/L respectively, satisfying the discharge requirement by Malaysia Department of Environment (DOE). The modeling study shows that the adsorption isotherm of boron onto POMB bottom ash conformed to the Freundlich Isotherm. The proposed method is suitable for boron removal in ceramic wastewater especially in regions where POMB bottom ash is abundant.
    Matched MeSH terms: Kinetics
  18. Ahmad AL, Sumathi S, Hameed BH
    Water Res, 2005 Jul;39(12):2483-94.
    PMID: 15985277
    The adsorption of residue oil from palm oil mill effluent (POME) using chitosan powder and flake has been investigated. POME contains about 2g/l of residue oil, which has to be treated efficiently before it can be discharged. Experiments were carried out as a function of different initial concentrations of residue oil, weight dosage, contact time and pH of chitosan in powder and flake form to obtain the optimum conditions for the adsorption of residue oil from POME. The powder form of chitosan exhibited a greater rate compared to the flake type. The results obtained showed that chitosan powder, at a dosage of 0.5g/l, 15min of contact time and a pH value of 5.0, presented the most suitable conditions for the adsorption of residue oil from POME. The adsorption process performed almost 99% of residue oil removal from POME. Equilibrium studies have been carried out to determine the capacity of chitosan for the adsorption of residue oil from POME using the optimum conditions from the flocculation at different initial concentrations of residue oil. Langmuir and Freundlich adsorption models were applied to describe the experimental isotherms and isotherm constants. Equilibrium data fitted very well with the Freundlich model. The pseudo first- and second-order kinetic models and intraparticle diffusion model were used to describe the kinetic data and the rate constants were evaluated. The experimental data fitted well with the second-order kinetic model, which indicates that the chemical sorption is the rate-limiting step, i.e. chemisorption between residue oil and chitosan. The significant uptake of residue oil on chitosan was further proved by BET surface area analysis and SEM micrographs.
    Matched MeSH terms: Kinetics
  19. Isa MH, Ezechi EH, Ahmed Z, Magram SF, Kutty SR
    Water Res, 2014 Mar 15;51:113-23.
    PMID: 24412846 DOI: 10.1016/j.watres.2013.12.024
    This work investigated the removal of boron from wastewater and its recovery by electrocoagulation and hydrothermal mineralization methods respectively. The experimental design was developed using Box-Behnken Model. An initial study was performed based on four preselected variables (pH, current density, concentration and time) using synthetic wastewater. Response surface methodology (RSM) was used to evaluate the effect of process variables and their interaction on boron removal. The optimum conditions were obtained as pH 6.3, current density 17.4 mA/cm(2), and time 89 min. At these applied optimum conditions, 99.7% boron removal from an initial concentration of 10.4 mg/L was achieved. The process was effectively optimized by RSM with a desirability value of 1.0. The results showed that boron removal efficiency enhanced with increase in current density and treatment time. Removal efficiency also increased when pH was increased from 4 to 7 and subsequently decreased at pH 10. Adsorption kinetics study revealed that the reaction followed pseudo second order kinetic model; evidenced by high correlation and goodness of fit. Thermodynamics study showed that mechanism of boron adsorption was chemisorption and the reaction was endothermic in nature. Furthermore, the adsorption process was spontaneous as indicated by negative values of the adsorption free energy. Treatment of real produced water using electrocoagulation resulted in 98% boron removal. The hydrothermal mineralization study showed that borate minerals (Inyoite, Takadaite and Nifontovite) can be recovered as recyclable precipitate from electrocoagulation flocs of produced water.
    Matched MeSH terms: Kinetics
  20. Lim PE, Ong SA, Seng CE
    Water Res, 2002 Feb;36(3):667-75.
    PMID: 11827329
    The application of simultaneous adsorption and biodegradation processes in the same reactor is known to be effective in the removal of both biodegradable and non-biodegradable contaminants in various kinds of wastewater. The objective of this study is to evaluate the efficacy of the two processes under sequencing batch reactor (SBR) operation in treating copper and cadmium-containing synthetic wastewater with powdered activated carbon (PAC) as the adsorbent. The SBR systems were operated with FILL, REACT, SETTLE, DRAW and IDLE periods in the ratio of 0.5: 3.5: 1.0: 0.75 :0.25 for a cycle time of 6 h. In the presence of 10 mg/L Cu(II) and 30 mg/L Cd(II), respectively, the average COD removal efficiencies were above 85% with the PAC dosage in the influent solution at 143 mg/L compared to around 60% without PAC addition. Copper(II) was found to exert a more pronounced inhibitory effect on the bioactivity of the microorganisms compared to Cd(II). It was observed that the combined presence of Cu(II) and Cd(II) did not exert synergistic effects on the microorganisms. Kinetic study conducted for the REACT period showed that the addition of PAC had minimized the inhibitory effect of the heavy metals on the bioactivity of microorganisms.
    Matched MeSH terms: Kinetics
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