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Mg Dm (mg + dm)
Selected AbstractsSorption of copper by a highly mineralized peat in batch and packed-bed systemsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2010Marta Izquierdo Abstract BACKGROUND: The performance of peat for copper sorption was investigated in batch and fixed-bed experiments. The effect of pH was evaluated in batch experiments and the experimental data were fitted to an equilibrium model including pH dependence. Hydrodynamic axial dispersion was estimated by tracing experiments using LiCl as a tracer. Six fixed-bed experiments were carried out at copper concentrations between 1 and 60 mg dm,3 and the adsorption isotherm in dynamic mode was obtained. A mass transport model including convection,dispersion and sorption processes was applied for breakthrough curve modelling. RESULTS: Maximum uptake capacities in batch mode were 22.0, 36.4, and 43.7 mg g,1 for pH values of 4.0, 5.0, and 6.0, respectively. Uptake capacities in continuous flow systems varied from 36.5 to 43.4 mg g,1 for copper concentrations between 1 and 60 mg dm,3. Dynamic and batch isotherms showed different shapes but a similar maximum uptake capacity. Sorbent regeneration was successfully performed with HCl. A potential relationship between dispersion coefficient and velocity was obtained with dispersion coefficients between 5.00 × 10,8 and 2.95 × 10,6 m2 s,1 for water velocities ranging between 0.56 × 10,4 and 5.03 × 10,4 m s,1. The mass transport model predicted both the breakpoints and the shape of the breakthrough curves. CONCLUSIONS: High retention capacities indicate that peat can be used as an effective sorbent for the treatment of wastewater containing copper ions. Copyright © 2009 Society of Chemical Industry [source] Adsorption of fulvic acids from aqueous solutions by carbon nanotubesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2007Shu-Guang Wang Abstract Carbon nanotubes (CNTs) were used as adsorbent to remove fulvic acids (FA) from aqueous solutions. The adsorption capacity of CNTs for FA can reach 24 mg g,1 at 5 °C and equilibrium concentration of 18 mg dm,3. The kinetic and thermodynamic parameters, such as rate of adsorption, standard free energy changes (,G0), standard enthalpy change (,H0) and standard entropy change (,S0), have been obtained. Acidic conditions (pH = 2,5) favor FA removal. An increase in the ionic strength or the addition of divalent cations increase the adsorption of FA dramatically (FA = 60 mg dm,3). An increase in the maximum adsorbed amount of FA was observed when treating FA in synthetic seawater. Desorption studies reveal that FA can be easily and quickly removed from CNTs by altering the pH values of the solution. Good adsorption capacity and quick desorption indicate that CNTs are a promising adsorbent to remove FA from aqueous solutions. Copyright © 2007 Society of Chemical Industry [source] Treatment of Fenton-refractory olive oil mill wastes by electrochemical oxidation with boron-doped diamond anodesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2006Pablo Cañizares Abstract In this work, the electrochemical oxidation of an actual industrial waste with conductive diamond anodes has been studied. The wastewater is the effluent of a wastewater treatment plant consisting of a Fenton reactor followed by a settler and a sand filter, in which the wastes generated in an olive oil mill are treated. These wastes contain a residual chemical oxygen demand of nearly 700 mg dm,3 which cannot be further oxidized with the Fenton process. The electrolyses were carried out under galvanostatic conditions, using a bench-scale plant equipped with a single-compartment electrochemical flow cell. Boron-doped diamond (BDD) and stainless steel (AISI 304) were use as anode and cathode of the cell, respectively. The complete mineralization of the waste was obtained with high current efficiencies limited only by mass transport processes. This confirms that besides the hydroxyl radical-mediated oxidation that occurs in the Fenton process, the electrochemical oxidation with conductive diamond electrodes combines other important oxidation processes such as direct electro-oxidation on the BDD surface and oxidation mediated by other electrochemically formed compounds generated in this electrode. Copyright © 2006 Society of Chemical Industry [source] Mn-peroxidase production by Panus tigrinus CBS 577.79: response surface optimisation and bioreactor comparisonJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2006Daniele Quaratino Abstract This study reports the statistical optimisation through response surface methodology of the growth medium for Panus tigrinus manganese-dependent peroxidase (MnP) production in shaken culture. Three crucial variables, including carbon source, malonic acid and Mn2+, were optimised in a nitrogen-limited medium. Sucrose was the best carbon source for MnP production. Mn2+ ions and malonic acid significantly stimulated MnP production at an optimal concentration of 53 mg dm,3 and 8.2 mmol dm,3, respectively, resulting in 0.83 U cm,3. Further experiments were performed in lab-scale stirred tank (STR) and bubble-column (BCR) reactors using the previously optimised liquid medium. BCR proved to be more adequate than STR in supporting MnP production, leading to 3700 U dm,3 after 144 h with a productivity of 25.7 U dm,3 h,1. On a comparative basis with other production data in lab-scale reactors, these results appear to be compatible with scale transfer. Copyright © 2006 Society of Chemical Industry [source] Performance assessment of a UASB,anoxic,oxic system for the treatment of tomato-processing wastesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2006Alpesh Gohil Abstract An upflow anaerobic sludge blanket (UASB),anoxic,oxic system was used to achieve biochemical oxygen demand, NH4 and total suspended solids (TSS) criteria of 15, 1 and 15 mg dm,3 at 1.17 days of system hydraulic retention time during treatment of tomato-processing waste. The incorporation of an anoxic tank was found to affect the improvement in sludge-settling characteristics, as reflected by about 25,33% reduction in the sludge volume index, along with final effluent TSS and soluble biochemical oxygen demand concentrations of 13 and 9 mg dm,3, respectively, which met the discharge criteria. Despite incomplete denitrification, sludge settleability was very good (sludge volume index < 60 cm3 g,1) owing to reduction in volatile suspended solids/TSS ratio from 0.75 to 0.6 as a result of higher alkalinity in the UASB effluent. Also in this study, phosphorus release was observed in the anoxic tank, predominantly due to abundance of acetic acid in the UASB effluent. A phosphate release of 5.4 mg P dm,3 was observed in the anoxic tank with subsequent P uptake in the following aerobic stage. Copyright © 2006 Society of Chemical Industry [source] Enhanced photodegradation of bisphenol A in the presence of ,-cyclodextrin under UV lightJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2006Guanghui Wang Abstract Enhancement of the photodegradation of bisphenol A (BPA) by ,-cyclodextrin (,-CD) was investigated under a 30 W UV disinfection lamp (,max = 254 nm). The photodegradation rate of BPA in aqueous solutions with ,-CD was faster than that in aqueous solutions without ,-CD; for example, after 50 min of UV irradiation, ,-CD had increased the photodegradation efficiency by about 46.5% for 10 mg dm,3 BPA. The photodegradation of 2.5,20 mg dm,3 BPA in aqueous solutions was found to follow pseudo-first-order kinetics. The first-order rate constant showed a 12-fold increase in the presence of ,-CD. Factors such as ,-CD concentration, pH, BPA initial concentration and organic solvent influencing the photodegradation of BPA were studied and are described in detail. Variations in the pH and electrical conductivity of solutions were observed during the photodegradation process. The enhancement of photodegradation of BPA results mainly from the lower bond energy between some atoms in the BPA molecule after inclusion interaction with ,-CD. Copyright © 2006 Society of Chemical Industry [source] Treatment of low turbidity water by sweep coagulation using bentoniteJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2005Yun-Hwei Shen Abstract A novel strategy of sweep coagulation to treat low turbidity water is presented herein. Study findings demonstrated that an Na+ -saturated bentonite with medium cation exchange capacity (CEC) resulted in significant turbidity removal at a bentonite dosage of 30 mg dm,3. Bentonite dispersion with fully delaminated platelets tended to undergo a more porous type of coagulation with intense face-to-face interactions of platelets and effectively entrapped TiO2 particles in band-type structures. This type of coagulation usually results in a large volume of settled flocs with a fluffy structure and excellent turbidity removal efficiency for sweep coagulation. The sign and magnitude of electrical charge on TiO2 particles has a minor effect on the efficiency of sweep coagulation. Copyright © 2005 Society of Chemical Industry [source] Effects of cationic polymer on start-up and granulation in upflow anaerobic sludge blanket reactorsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2004Ying Wang Abstract The upflow anaerobic sludge blanket (UASB) has been used successfully to treat a variety of industrial wastewaters. It offers a high degree of organics removal, low sludge production and low energy consumption, along with energy production in the form of biogas. However, two major drawbacks are its long start-up period and deficiency of active biogranules for proper functioning of the process. In this study, the influence of a coagulant polymer on start-up, sludge granulation and the associated reactor performance was evaluated in four laboratory-scale UASB reactors. A control reactor (R1) was operated without added polymer, while the other three reactors, designated R2, R3 and R4, were operated with polymer concentrations of 5 mg dm,3, 10 mg dm,3 and 20 mg dm,3, respectively. Adding the polymer at a concentration of 20 mg dm,3 markedly reduced the start-up time. The time required to reach stable treatment at an organic loading rate (OLR) of 4.8 g COD dm,3 d,1 was reduced by more than 36% (R4) as compared with both R1 and R3, and by 46% as compared with R2. R4 was able to handle an OLR of 16 g COD dm,3 d,1 after 93 days of operation, while R1, R2 and R3 achieved the same loading rate only after 116, 116 and 109 days respectively. Compared with the control reactor, the start-up time of R4 was shortened by about 20% at this OLR. Granule characterization indicated that the granules developed in R4 with 20 mg dm,3 polymer exhibited the best settleability and methanogenic activity at all OLRs. The organic loading capacities of the reactors were also increased by the addition of polymer. The maximum organic loading of the control reactor (R1) without added polymer was 19.2 g COD dm,3 d,1, while the three polymer-assisted reactors attained a marked increase in organic loading of 25.6 g COD dm,3 d,1. Adding the cationic polymer could result in shortening of start-up time and enhancement of granulation, which may in turn lead to improvement in the efficiency of organics removal and loading capacity of the UASB system. Copyright © 2004 Society of Chemical Industry [source] Electrolytic removal of ammonia from brine wastewater: scale-up, operation and pilot-scale evaluationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2004Catalino G Alfafara Abstract Brine wastewater with a high ammonia content from an iodine processing plant (commonly called kansui in Japan) was treated by electrolysis. The system, which can be considered as an indirect electrolytic treatment process, generates chlorine at the anodes and initiates the formation of mixed oxidants like hypochlorous acid. The oxidants then act as agents for ammonia destruction. Laboratory-scale experiments showed that high ammonia concentrations (as much as 200 mg dm,3) could be completely removed within a few minutes, and could be considered a good alternative for efficient ammonia removal from saline wastewaters. From laboratory-scale experiments in the batch and continuous modes, the charge dose was analyzed and used as the operating and scale-up factor. The value of the charge dose was not severely affected by changes in operating conditions such as electrode spacing and temperature. The charge dose from batch and continuous runs was found to be in the range of 23 C (mg NH4 -N removed),1 to 29 C (mg NH4 -N removed),1. Using the charge dose obtained from laboratory-scale continuous electrolysis experiments as the scale-up factor, a pilot-scale reactor was designed, and the operating conditions were calculated. In the pilot-scale reactor tests at different flow rates, the effluent ammonia concentrations were reasonably close to the calculated values predicted from the charge dose equation. Copyright © 2004 Society of Chemical Industry [source] The use of 3,3,,4,,5-tetrachlorosalicylanilide as a chemical uncoupler to reduce activated sludge yieldJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2004Ying Xu Chen Abstract To determine whether chemical additions can be used to reduce sludge production in biological wastewater treatment, 3,3,,4,,5-tetrachlorosalicylanilide (TCS) was added to activated sludge cultures as a metabolic uncoupler. Batch tests confirmed that TCS is an effective chemical uncoupler in reducing the sludge yield at concentrations greater than 1.0 mg dm,3; a TCS concentration of 1.0 mg dm,3 reduced sludge yield by approximately 50%. Substrate removal capability and effluent nitrogen concentration were not affected adversely by the presence of TCS when dosed every other day in a range of 2.0,3.6 mg dm,3 during the 40-day operation of activated sludge batch cultures. Such sludge growth reduction was associated with the enhancement of microbial activities in terms of the specific oxygen uptake rate and dehydrogenase activity. Sludge settleability of the treated and control samples was qualitatively comparable and not significantly different. Filamentous bacteria continued to grow in sludge flocs only in the control reactor at the end of the 40-day trial. These results suggest that TCS treatment of activated sludge systems may reduce excess sludge yield. Copyright © 2003 Society of Chemical Industry [source] Removal of cadmium from dilute aqueous solutions with a rotating cylinder electrode of expanded metalJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2003Javier M Grau Abstract The removal of cadmium from dilute solutions using a continuous undivided electrochemical reactor with a rotating cylinder cathode of expanded metal is analysed. The effects of cathodic applied potential, size and orientation of expanded metal meshes and inlet cadmium concentration were ascertained. The results show that cadmium can be removed from dilute solutions (inlet concentration range 5,50 mg dm,3) with a high fractional conversion of between 35 and 40% depending on the operating conditions. Thus a minimal residual cadmium concentration of 3 mg dm,3 was achieved. The specific energy consumption increases from 0.6 to 2 kWh mol,1 as the cadmium concentration decreases. Copyright © 2003 Society of Chemical Industry [source] Studies on internal and external water treatment at a paper and cardboard factoryJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2003Mamdouh M Nassar Abstract The treatment of effluent from a paper/board factory that produced 280 tons of cardboard and consumed 1200 m3 of water per day was carried out. Wastewater analysis showed that the mill effluent contained 3000 mg dm,3 suspended solids, 1400 mg dm,3 COD (chemical oxygen demand) and 500 mg dm,3 BOD (biochemical oxygen demand). An internal treatment cycle is suggested that involves recirculation of paper-machine wastewater (white-water) and may be accomplished by installing a flotation saveall (fiber recovery) unit. This arrangement reduced fresh water use by about 90%, reduced fiber loss by 80,90%, and increased board production by 13%. An external treatment process for the effluent was assessed by conducting laboratory coagulation tests (alum, ferric chloride, ferrous sulfate, and polyelectrolyte) on the whole mill effluent. Oxidation of the mill effluent using calcium hypochlorite before discharging the effluent to a lagoon offers the benefits of killing the harmful bacteria and reducing the pollution load. Copyright © 2003 Society of Chemical Industry [source] Accumulation of arsenic by Traustochytrium sp.APPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2002CHN-1 from Seto Inland Sea Abstract The accumulation of arsenic by Traustochytrium sp. CHN-1 (Labyrinthulids) was examined by using a medium [2% (w/v) glucose, 0.1% (w/v) yeast extract, 0.1% (w/v) peptone in a half salt concentration of sea water] containing arsenic as As(V), As(III). Traustochytrium sp. CHN-1 was grown in 1/2 sea water medium [2% (w/v) glucose, 0.1% (w/v) yeast extract, 0.1% (w/v) peptone] containing an arsenate (As(V)) at up to 1000,mg dm,3 and arsenite (As(III)) at up to 50,mg dm3. The cells died even at [As(III)]-100,mg dm,3. These results suggested that the order of growth inhibition of Traustochytrium sp. CHN-1 by arsenic was As(III),>,As(V). The biomass of Traustochytrium sp. CHN-1 decreased with an increase of the surrounding arsenic concentration. On the other hand, the arsenic concentration in cells increased with an increase of the surrounding arsenic concentration. Arsenic compounds were extracted with methanol/water (1:1) from a freeze-dried sample of Traustochytrium sp. CHN-1. The extracts were analyzed by high-performance liquid chromatography, with an inductively coupled plasma mass spectrometer serving as an arsenic-specific detector. Arsenite, arsenate, monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA) and arsenosugar were identified in Traustochytrium sp. CHN-1. The order of arsenic species in Traustochytrium sp. CHN-1 was As(V),>,DMAA,>,As(III),>,MMAA,>,arsenosugar at [As]-10,mg dm,3 in the medium. Detoxification of arsenic by cells was probably achieved by methylation. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||