Upgrading sewage sludges for adsorbent preparation by different treatments

Addressing the adequate management of sludges produced at sewage plants is becoming a fundamental need as a consequence of the high production volumes, both current and forecasted, of this byproduct. European waste-treatment policies consider reuse of sludges as one of the preferred actions; along those lines this study proposes using sewage sludges as adsorbents for pollutants contained in wastewaters. As potential adsorbents, sludges dried at 105 degrees C, dried and pyrolyzed, or dried and chemically activated were tried. As adsorbate, methylene blue was used in order to characterize the adsorption capacity of the different materials. Although surface areas corresponding to pyrolyzed and chemically activated sludges were around 80 and 390 m2/g, respectively, both these materials exhibited poor levels of methylene blue adsorption which may have been due to their high proportions of micropores. Sludges only dried, on the contrary, showed significant methylene blue adsorption capacities.     

Preparation and characterization of activated carbon from sunflower seed oil residue via microwave assisted K2CO3 activation

Sunflower seed oil residue, a by-product of sunflower seed oil refining, was utilized as a feedstock for preparation of activated carbon (SSHAC) via microwave induced K(2)CO(3) chemical activation. SSHAC was characterized by Fourier transform infrared spectroscopy, nitrogen adsorption-desorption and elemental analysis. Surface acidity/basicity was examined with acid-base titration, while the adsorptive properties of SSHAC were quantified using methylene blue (MB) and acid blue 15 (AB). The monolayer adsorption capacities of MB and AB were 473.44 and 430.37 mg/g, while the Brunauer-Emmett-Teller surface area, Langmuir surface area and total pore volume were 1411.55 m(2)/g, 2137.72 m(2)/g and 0.836 cm(3)/g, respectively. The findings revealed the potential to prepare high surface area activated carbon from sunflower seed oil residue by microwave irradiation.     

Adsorption of Methylene Blue Dye on Pure and Carbonized Water Weeds

The influence of process variables in batch adsorption has been used to assess the removal of methylene blue dye from aqueous solution using pure and carbonized biomasses of water hyacinth and water spinach. Dried leaves of the water weeds were carbonized at temperature up to 750°C. The optimum removal of dye was achieved at pH 10, 30°C, and 55 min at a dye concentration of 10 mg/L. In an attempt to describe the adsorption process, the equilibrium isotherm for each adsorbent was determined using Langmuir and Freundlich adsorption isotherm models. Maximum adsorption capacities based on the Langmuir model for pure and carbonized water hyacinth were (mg/g) 7.05 and 2.07, respectively, whereas those of pure and carbonized water spinach were 1.25 and 5.32, respectively. It was observed that the equilibrium data were well fit by both the Freundlich and Langmuir isotherms as R ² > .97. This study demonstrates that the two waterweeds are effective, environmentally friendly, and inexpensive biomaterials for the removal of color from industrial effluents.     

利用水蒸气活化稻壳生产活性炭的研究

研究了水蒸气法活化制备稻壳活性炭的工艺条件,探讨了炭化温度、活化温度、活化时间和水蒸气用量对活化效果的影响。结果表明最佳工艺条件为:炭化温度450℃、活化温度900℃、活化时间90 min和水蒸气用量为炭化料的1.5倍,制备的活性炭碘值844 mg/g,亚甲基蓝吸附值138 mL/g。这些指标与木质活性炭相当。且投资少,能耗低,具有良好的社会效益与经济效益。     

Chemical activation of hickory and peanut hull hydrochars for removal of lead and methylene blue from aqueous solutions

Hickory and peanut hydrochars were chemically activated with KOH and H₃PO₄ and tested for their ability to remove methylene blue and lead from aqueous solutions. The physicochemical characteristics of the activated hydrochars determined were surface area, pore volume, and elemental composition. Kinetics and isotherm studies were then conducted on methylene blue adsorption. Compared to their nonactivated counterparts, the chemically activated hydrochars had higher surface areas and more functional groups. Activated hydrochars also had greater methylene blue and lead adsorption rates, which can be attributed to the improved physicochemical characteristics. H₃PO₄ activated hydrochars removed more contaminants than the corresponding KOH ones.     

Preparation and characterization of activated carbon produced from rice straw by (NH4)2HPO4 activation

Effects of different pretreatment protocols in (NH(4))(2)HPO(4) activation of rice straw on porous activated carbon evolution were evaluated. The pore structure, morphology and surface chemistry of obtained activated carbons were investigated by nitrogen adsorption, scanning electron microscopy and Fourier transform infrared spectroscopy. It was found that pretreatment combining impregnation with (NH(4))(2)HPO(4) and preoxidation could significantly affect the physicochemical properties of prepared activated carbons. The apparent surface area and total pore volume as high as 1154 m(2)/g and 0.670 cm(3)/g were obtained respectively, when combined process of impregnation followed by preoxidation at 200°C and activation at 700°C was carried out. Meanwhile, the activated carbon yield and maximum methylene blue adsorption capacity up to 41.14% and 129.5 mg/g were achieved, respectively. The results exhibited that (NH(4))(2)HPO(4) could be an effective activating agent for producing activated carbons from rice straw.     

Removal of hexavalent chromium using a novel cross linked xanthated chitosan

Suitability of a novel cross linked, chemically modified chitosan as highly efficient adsorbent for the recovery of toxic chromium(VI) was studied. After cross linking with glutaraldehyde, xanthate group was grafted onto the back bone of chitosan. Sorption was found to be both pH and concentration dependent, with pH 3 being the optimum value. Both, chemically modified beads (CMCB) and flakes (CMCF) followed a pseudo-second-order kinetics with a rate constant of 2.037 and 4.639 g/mg/min, respectively. The equilibrium data followed the Langmuir isotherm model with maximum capacities of 625 mg/g and 256.4 mg/g and for CMCF and CMCB respectively. Desorption studies revealed the reusability of the sorbent for at least 10 cycles without any significant change in adsorption capacities.     

Fate and effects of methylene chloride in activated sludge.

Activated sludge obtained from a municipal wastewater treatment plant was acclimated to methylene chloride at concentrations between 1 and 100 mg/liter by continuous exposure to the compound for 9 to 11 days. Acclimated cultures were shown to mineralize methylene chloride to carbon dioxide and chloride. Rates of methylene chloride degradation were 0.14, 2.3, and 7.4 mg of CH2Cl2 consumed per h per g of mixed-liquor suspended solids for cultures incubated in the presence of 1, 10, and 100 mg/liter, respectively. Concentrations of methylene chloride between 10 and 1,000 mg/liter had no significant effect on O2 consumption or glucose metabolism by activated sludge. A hypothetical model was developed to examine the significance of volatilization and biodegradation for the removal of methylene chloride from an activated sludge reactor. Application of the model indicated that the rate of biodegradation was approximately 12 times greater than the rate of volatilization. Thus, biodegradation may be the predominant process determining the fate of methylene chloride in activated sludge systems continuously exposed to the compound.     

Experimental and kinetic studies on methylene blue adsorption by coir pith carbon

Varying the parameters such as agitation time, dye concentration, adsorbent dose, pH and temperature carried out the potential feasibility of thermally activated coir pith carbon prepared from coconut husk for removal of methylene blue. Greater percentage of dye was removed with decrease in the initial concentration of dye and increase in amount of adsorbent used. Kinetic study showed that the adsorption of dye on coir pith carbon was a gradual process. Lagergren first-order, second-order, intra particle diffusion model and Bangham were used to fit the experimental data. Equilibrium isotherms were analysed by Langmuir, Freundlich, Dubnin-Radushkevich, and Tempkin isotherm. The adsorption capacity was found to be 5.87 mg/g by Langmuir isotherm for the particle size 250-500 microm. The equilibrium time was found to be 30 and 60 min for 10 and 20 mg/L and 100 min for 30, 40 mg/L dye concentrations, respectively. A maximum removal of 97% was obtained at natural pH 6.9 for an adsorbent dose of 100 mg/50 mL and 100% removal was obtained for an adsorbent dose of 600 mg/50 mL of 10 mg/L dye concentration. The pH effect and desorption studies suggest that chemisorption might be the major mode of the adsorption process. The change in entropy (DeltaS0) and heat of adsorption (DeltaH0) of coir pith carbon was estimated as 117.20 J/mol/K and 30.88 kJ/mol, respectively. The high negative value of change in Gibbs free energy indicates the feasible and spontaneous adsorption of methylene blue on coir pith carbon.     

Effect of nitrogen source concentration on decolouration rates of laboratory dyes by immobilized cells of two bacterial species

The aim of this study was to assess the effect of sodium nitrate concentration on the decolouration of laboratory dyes (bromothymol blue, crystal violet, eosin blue, eosin yellow and methylene blue), by alginate immobilized cells of Pseudomonas aeruginosa and Bacillus subtilis. The sodium nitrate concentrations used in the study were 5, 10, 15 and 20 g/L. A control setup that contained no sodium nitrate was also studied. During incubation, aliquot samples were withdrawn from each flask every 24 for 144 h duration for the estimation of decolouration rate of the dyes, using standard procedures. The results revealed remarkable decolouration of the bromothymol blue and crystal violet in presence of the P. aeruginosa occurring at sodium nitrate concentrations of 10 and 15 g/L, respectively. In the case of media that was inoculated with the B. subtilis cells, although no remarkable decolouration of the bromothymol blue and crystal violet was observed throughout the period of incubation, highest decolouration were observed at sodium nitrate concentration of 5 and 10 g/L, respectively. For the eosin blue and methylene dyes, no remarkable decolouration were observed in presence of the test bacterial species at the respective sodium nitrate concentrations. Highest decolouration of the eosin yellow was however observed in media with sodium nitrate concentration of 5 g/L. The results of this study could be applied in scale up studies and continuous process, for implementation in biological decolouration of dye effluents.     

Utilization of rice husks as a feedstock for preparation of activated carbon by microwave induced KOH and K2CO3 activation

Rice husk (RH), an abundant by-product of rice milling, was used for the preparation of activated carbon (RHAC) via KOH and K(2)CO(3) chemical activation. The activation process was performed at the microwave input power of 600 W for 7 min. RHACs were characterized by low temperature nitrogen adsorption/desorption, scanning electron microscopy and Fourier transform infrared spectroscopy. The adsorption behavior was examined using methylene blue as adsorbate. The K(2)CO(3)-activated sample showed higher yield and better pore structures and adsorption capacity development than the KOH-activated sample, with a BET surface area, total pore volume and monolayer adsorption capacity of 1165 m(2)/g, 0.78 cm(3)/g and 441.52 mg/g, respectively. The results revealed the feasibility of microwave heating for preparation of high surface area activated carbons from rice husks via K(2)CO(3) activation.     

Adsorption of methylene blue from aqueous solution on pyrolyzed petrified sediment

The adsorption kinetics of methylene blue on pyrolyzed petrified sediment (PPS) has been performed using a batch-adsorption technique. The effects of various experimental parameters, such as initial dye concentration, contact time, and temperature were investigated. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data. The best correlation coefficient was obtained using the pseudo first-order kinetic model, which shows that the adsorption of methylene blue followed the pseudo-first-order rate expression and the rate constants were evaluated. The Langmuir and Freundlich adsorption isotherm models were applied to describe the equilibrium isotherms and the isotherm constants were determined. It was found that the data fitted well to Langmuir and Freundlich models. The activation energy of adsorption was also evaluated for the adsorption of methylene blue onto pyrolyzed sediment. It was found about 8.5 kJ mol(-1). Thermodynamics parameters DeltaG(o), DeltaH(o), DeltaS(o) were calculated, indicating that this process can be spontaneous and endothermic. The adsorption enthalpy and entropy were found as 14-18.5 kJ mol(-1) and 52.8-67 J mol(-1) K(-1), respectively. The results obtained from the adsorption process using PPS as adsorbent was subjected to student's t-test.     

Zinc Chloride Methylene Blue, Ii. Preparation of Giesma and Wright Type Low Azure B Blood Stains from Dichromate Oxidized Commercial Dye

TO determine the amount of K₂Cr₂O₇ required to produce optimal Giemsa type staining, six 1 g amounts (corrected for dye content) of zinc methylene blue were oxidized with graded quantities of K₂Cr₂O₇ to produce 4, 8, 12, 16, 20 and 24% conversion of methylene blue to azure B. These were heated with a blank control 15 minutes at 100 C in 60-65 ml 0.4 N HCI. cooled, and adjusted to 50 ml to give 20 mg original dye/ml. Aliquots were then diluted to 1% and stains were made by the “Wet Giemsa” technic (Lillie and Donaldson 1979) using 6 ml 1% polychrome methylene blue, 4 ml 1% cosin (corrected for dye content), 2 ml 0.1 M pH 6.3 phosphate buffer, 5 ml acetone, and 23 ml distilled water. The main is added last and methanol fixed blood films are stained immediately for 20-40 min.

For methylene blue supplied by MCB 12-H-29, optimal stains were obtained with preparations containing 20 and 24% conversion of methylene blue to azure B. With methylene blue supplied by Aldrich (080787), 16% conversion of methylene blue to azure B was optimal. Eosinates prepared from a low azure B/methylene blue preparation selected in this way give good stains when used as a Wright stain in 0.3% methanol solution. However, when the 600 mg eosinate solution in glycerol methanol is supplemented with 160 mg of the same azure B/methylene blue chloride the mixture fails to perform well. The HCI precipitation of the chloride apparently produces the zinc methylene blue chloride salt which is poorly soluble in alcohol. It appears necessary to have a zinc-free azure B/methylene blue chloride to supplement the probably zinc-free eosinate used in the Giemsa mixture.     

Microwave-assisted preparation and adsorption performance of activated carbon from biodiesel industry solid reside: influence of operational parameters

Preparation of activated carbon has been attempted using KOH as activating agent by microwave heating from biodiesel industry solid residue, oil palm empty fruit bunch (EFBAC). The significance of chemical impregnation ratio (IR), microwave power and activation time on the properties of activated carbon were investigated. The optimum condition has been identified at the IR of 1.0, microwave power of 600 W and activation time of 7 min. EFBAC was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption isotherm. The surface chemistry was examined by zeta potential measurement, determination of surface acidity/basicity, while the adsorptive property was quantified using methylene blue as dye model compound. The optimum conditions resulted in activated carbon with a monolayer adsorption capacity of 395.30 mg/g and carbon yield of 73.78%, while the BET surface area and total pore volume were corresponding to 1372 m²/g and 0.76 cm³/g, respectively.     

Activated carbon from Eucalyptus camaldulensis Dehn bark using phosphoric acid activation

The powdered activated carbon prepared by phosphoric acid activation was significantly affected by the carbonization temperature and the weight ratio between raw material and phosphoric acid. With an activation time of 1h and an impregnation ratio of 1:1, the activated carbons with better adsorption capacity were obtained at 500 degrees C. A reduction in the adsorption capacity of the carbon product at higher acid content than this was observed, possibly due to the collapse of the micropore structure. The properties of the resulting activated carbon were: bulk density 0.251gcm(-3), ash content 4.88%, yield 26.2%, iodine adsorption 1043mgg(-1), methylene blue adsorption number 427mgg(-1), and BET surface area 1239m(2)g(-1).     

Adsorption of Phenolic Compounds and Methylene Blue onto Activated Carbon Prepared from Date Fruit Pits

Activated carbon has been prepared from date fruit pits. The carbon, prepared at different burn‐off rates, showed a high uptake of methylene blue. At 92 % burn‐off (weight loss percent of the carbonized pits upon activation), methylene blue uptake was 590 mg/g. With this high capacity, the carbon was then used to study the adsorption of phenol, 2‐nitrophenol, 2,4‐dinitrophenol, and 2,4,6‐trinitrophenol. The prepared activated carbon showed an adsorption capacity better than that of many activated carbons in current use. The experimental adsorption data for the single components were regressed using both Langmuir and Freundlich isotherm models and the fit was generally satisfactory. The experimental adsorption data of the binary system phenol‐2‐nitrophenol were compared with the predicted results using two predictive models: the generalized Langmuir and the IAS models. The data were better represented by the IAS theory than the generalized Langmuir model even though the fit of the experimental data was not adequate.     

The membrane-bound hydrogenase from Paracoccus denitrificans. Purification and molecular characterization

The membrane-bound hydrogenase from Paracoccus denitrificans was purified 68-fold with a yield of 14.6%. The final preparation had a specific activity of 161.9 mumol H2 min-1 (mg protein)-1 (methylene blue reduction). Purification involved solubilization by Triton X-114, phase separation, chromatography on DEAE-Sephacel, ammonium-sulfate precipitation and chromatography on Procion-red HE-3B-Sepharose. Gel electrophoresis under denaturing conditions revealed two non-identical subunits with molecular masses of 64 kDa and 34 kDa. The molecular mass of the native enzyme was 100 kDa, as estimated by FPLC gel filtration in the presence of Chaps, a zwitterionic detergent. The isoelectric point of the Paracoccus hydrogenase was 4.3. Metal analysis of the purified enzyme indicated a content of 0.6 nickel and 7.3 iron atoms/molecule. ESR spectra of the reduced enzyme exhibited a close similarity to the membrane-bound hydrogenase from Alcaligenes eutrophus H16 with g values of 1.86, 1.92 and 1.98. The half-life for inactivation under air at 20 degrees C was 8 h. The Paracoccus hydrogenase reduced several electron acceptors, namely methylene blue, benzyl viologen, methyl viologen, menadione, cytochrome c, FMN, 2,6-dichloroindophenol, ferricyanide and phenazine methosulfate. The highest activity was measured with methylene blue (V = 161.9 U/mg; Km = 0.04 mM), whereas benzyl and methyl viologen were reduced at distinctly lower rates (16.5 U/mg and 12.1 U/mg, respectively). The native hydrogenase from P. denitrificans cross-reacted with purified antibodies raised against the membrane-bound hydrogenase from A. eutrophus H16. The corresponding subunits from both enzymes also showed immunological relationship. All reactions were of partial identity.     

Evaluation of a countercurrent biosorption system for the removal of lead and copper from aqueous solutions

Abstract: An automated bench-scale countercurrent biosorption system (CBS) has been designed for the removal of metals from aqueous effluents. The system has been tested with activated sludge microorganisms as a biosorbent and lead and copper as model metals. Nearly 5 1 of a lead nitrate solution at 100 mg l⁻¹ of lead have been treated down to a final concentration of 0.1 mg l⁻¹ (99.9% removal) by using 4.8 g of dry biosorbent. Under similar conditions, copper chloride solutions at 100 mg 1⁻¹ of copper were treated down to a final concentration of 35–45 mg l^−l representing 60% removal. The advantage of the CBS is to maximize metal concentration in the biosorbent, from which the metal may thereby be recovered if desired. In addition, the CBS minimizes metal concentration in the treated effluent, which is the first objective of the treatment.     

蔬菜吸收不同形态外源碘的动力学特性

采用水培法,研究了两种蔬菜(小白菜和芹菜)对两种不同形态碘源(I-,IO-3)的吸收和积累特性.结果表明:供试蔬菜吸收碘的速率表现为在短时间(＜60 min)内迅速增加,随着时间的延长蔬菜对碘的吸收速率逐渐下降;在低浓度范围内(0.01～0.50 mg/L)蔬菜对IO-3的吸收速率与碘浓度变化曲线符合饱和吸收动力学特征(表现为遵循酶学方程),进一步研究表明,解偶联剂2,4-二硝基苯酚(DNP)对低浓度(＜0.50 mg/L)下蔬菜IO-3吸收速率具有明显的抑制作用,说明两种蔬菜对低浓度的IO-3可能存在主动吸收,而在高浓度范围内(0.50～10.0 mg/L),蔬菜对碘的吸收速率随着碘浓度的提高呈现直线上升的趋势.两种蔬菜相比,在同样条件下芹菜对碘的吸收速率明显大于小白菜.蔬菜可食部分中碘的含量随着碘浓度的提高而增加,在一次加碘条件下表现为先增加后降低的趋势,而在持续加碘条件下蔬菜中碘的含量在整个处理期间表现为不断增加; Cl-的添加对低浓度下蔬菜碘的吸收具有明显的抑制作用,而随着碘浓度的提高Cl-的抑制作用逐渐减弱.供试蔬菜对碘的富集系数随碘浓度的提高而降低,碘在蔬菜不同器官的分配次序表现为根＞叶＞茎.     

The influence of NO synthase inhibitor and free oxygen radicals scavenger--methylene blue--on streptozotocin-induced diabetes in rats

The excessive production of nitric oxide (NO) and the subsequent increase of local oxidative stress is suggested as one of the pathophysiological mechanisms of streptozotocin-induced diabetes. It was reported that the administration of NO synthase inhibitors partially attenuated the development of streptozotocin-induced diabetes and reduced hyperglycaemia. Here we have studied the influence of methylene blue, which combines the properties of NO synthase inhibitor with antioxidant effects. The experiments were performed on male rats divided into four groups: control, diabetic (single dose of 70 mg of streptozotocin/kg i.p.), methylene blue (50 mg/kg in the food) and diabetic simultaneously fed with methylene blue. After 45 days the experiments were discontinued by decapitation. Serum glycaemia, glycated haemoglobin and oxidative stress parameters (plasma malondialdehyde concentration and erythrocyte superoxide dismutase activity) were significantly higher in the diabetic group. Simultaneous methylene blue administration partially reduced glycaemia and glycated haemoglobin, but did not decrease oxidative stress. We conclude that NO synthase inhibitor methylene blue partially attenuates the development of streptozotocin-induced diabetes in male rats, but does not reduce the development of oxidative stress in the diabetic group.