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.     

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.     

Activated carbons from waste biomass by sulfuric acid activation and their use on methylene blue adsorption

Preparation of the activated carbons from sunflower oil cake by sulphuric acid activation with different impregnation ratios was carried out. Laboratory prepared activated carbons were used as adsorbents for the removal of methylene blue (MB) from aqueous solutions. Liquid-phase adsorption experiments were conducted and the maximum adsorption capacity of each activated carbon was determined. The effects of various process parameters i.e., temperature, pH, initial methylene blue concentration, contact time on the adsorption capacity of each activated carbon were investigated. The kinetic models for MB adsorption onto the activated carbons were studied. Langmuir isotherm showed better fit than Freundlich isotherm for all activated carbon samples. The rates of adsorption were found to conform to the pseudo-second-order kinetics with good correlation. The separation factor (R(L)) revealed the favorable nature of the isotherm of the MB activated carbon system.     

Activated carbon from olive kernels in a two-stage process: industrial improvement

Activated carbons have been prepared from olive kernels and their adsorptive characteristics were investigated. A two stage process of pyrolysis-activation has been tested in two scales: (a) laboratory scale pyrolysis and chemical activation with KOH and (b) pilot/bench scale pyrolysis and physical activation with H(2)O-CO(2). In the second case, olive kernels were first pyrolysed at 800 degrees C, during 45 min under an inert atmosphere in an industrial pyrolyser with a throughput of 1t/h (Compact Power Ltd., Bristol, UK). The resulting chars were subsequently activated with steam and carbon dioxide mixtures at 970 degrees C in a batch pilot monohearth reactor at NESA facility (Louvain-la Neuve, Belgium). The active carbons obtained from both scales were characterized by N(2) adsorption at 77 K, methyl-blue adsorption (MB adsorption) at room temperature and SEM analysis. Surface area and MB adsorption were found to increase with the degree of burn-off. The maximum BET surface area was found to be around 1000-1200 m(2)/g for active carbons produced at industrial scale with physical activation, and 3049 m(2)/g for active carbons produced at laboratory with KOH activation. The pores of the produced carbons were composed of micropores at the early stages of activation and both micropores and mesopores at the late stages. Methylene blue removal capacity appeared to be comparable to that of commercial carbons and even higher at high degrees of activation.     

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.     

High performance biosorbent (Caulerpa lentillifera) for basic dye removal

The sorptions of three basic dyes, Astrazon((R)) Blue FGRL (AB), Astrazon((R)) Red GTLN (AR), and methylene blue (MB) onto green macroalga Caulerpa lentillifera were investigated. The results were compared to the sorption performance of a commercial activated carbon (CARBON). The results revealed that the alga exhibited greater sorption capacities than activated carbon for the three basic dyes investigated in this work. The sorption process for all mixture systems (ALGA/AB, ALGA/AR, ALGA/MB, CARBON/AB, CARBON/AR, and CARBON/MB) obeyed the pseudo-second order kinetic model. C. lentillifera could more rapidly sequester AR when compared with activated carbon, but was more slowly in the sorption of AB. For the sorption of MB, both ALGA and CARBON seemed to have the same sorption rate. The sorption processes were initially controlled by both film and pore-diffusion, and only were limited by pore diffusion in the later stage. The isotherms followed Langmuir model which suggested that the sorption was monolayer coverage.     

Physicochemical properties of carbons prepared from pecan shell by phosphoric acid activation

Activated carbons were prepared from pecan shell by phosphoric acid activation. The pore structure and acidic surface groups of these carbons were characterized by nitrogen adsorption, Boehm titration and transmittance Fourier infrared spectroscopy (FTIR) techniques. The characterization results demonstrated that the development of pore structure was apparent at temperatures 250 degrees C, and reached 1130m(2)/g and 0.34cm(3)/g, respectively, at 500 degrees C. Impregnation ratio and soaking time at activation temperature also affected the pore development and pore size distribution of final carbon products. At an impregnation ratio of 1.5, activated carbon with BET surface area and micropore volume as high as 861m(2)/g and 0.289cm(3)/g was obtained at 400 degrees C. Microporous activated carbons were obtained in this study. Low impregnation ratio (less than 1.5) and activation temperature (less than 300 degrees C) are favorable to the formation of acidic surface functional groups, which consist of temperature-sensitive (unstable at high temperature) and temperature-insensitive (stable at high temperature) two parts. The disappearance of temperature-sensitive groups was significant at temperature 300 degrees C; while the temperature-insensitive groups are stable even at 500 degrees C. FTIR results showed that the temperature-insensitive part was mostly phosphorus-containing groups as well as some carbonyl-containing groups, while carbonyl-containing groups were the main contributor of temperature-sensitive part.     

Optimization of microporous palm shell activated carbon production for flue gas desulphurization: experimental and statistical studies

Optimizing the production of microporous activated carbon from waste palm shell was done by applying experimental design methodology. The product, palm shell activated carbon was tested for removal of SO2 gas from flue gas. The activated carbon production was mathematically described as a function of parameters such as flow rate, activation time and activation temperature of carbonization. These parameters were modeled using response surface methodology. The experiments were carried out as a central composite design consisting of 32 experiments. Quadratic models were developed for surface area, total pore volume, and microporosity in term of micropore fraction. The models were used to obtain the optimum process condition for the production of microporous palm shell activated carbon useful for SO2 removal. The optimized palm shell activated carbon with surface area of 973 m(2)/g, total pore volume of 0.78 cc/g and micropore fraction of 70.5% showed an excellent agreement with the amount predicted by the statistical analysis. Palm shell activated carbon with higher surface area and microporosity fraction showed good adsorption affinity for SO2 removal.     

Preparation of activated carbons from cattle-manure compost by zinc chloride activation

Dried cattle-manure compost was pyrolyzed by a one-step process to obtain activated carbon using chemical activation by zinc chloride. The influence of activation parameters such as ZnCl(2) to cattle-manure compost (ZnCl(2)/CMC) ratio, activation temperature and retention time on the final products was investigated. The resultant activated carbons were characterized by nitrogen adsorption-desorption isotherms at 77 K. The results showed that the surface area and pore volume of activated carbons, which were estimated by BET and t-plot methods, were achieved as high as 2170 m(2)/g and 1.70 cm(3)/g in their highest value, respectively. Thermogravimetric analysis (TGA) was carried out to monitor the pyrolysis process of cattle-manure compost (CMC) and ZnCl(2) impregnated one (ZnCl(2)/CMC). The capabilities of phenol adsorption were also examined for the CMC carbons prepared with various treatments.     

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).     

Preparation and characterization of activated carbon from palm shell by chemical activation with K2CO3

Palm shell was used to prepare activated carbon using potassium carbonate (K2CO3) as activating agent. The influence of carbonization temperatures (600-1000 degrees C) and impregnation ratios (0.5-2.0) of the prepared activated carbon on the pore development and yield were investigated. Results showed that in all cases, increasing the carbonization temperature and impregnation ratio, the yield decreased, while the adsorption of CO2 increased, progressively. Specific surface area of activated carbon was maximum about 1170 m2/g at 800 degrees C with activation duration of 2 h and at an impregnation ratio of 1.0.     

Adsorption of methylene blue using green pea peels (Pisum sativum): A cost-effective option for dye-based wastewater treatment

Methylene blue (MB), a common toxic dye, is largely discharged from dyeing processes for acrylic, nylon, silk, and woolen fabrics in textile industries. While application of conventional removal processes like chemical precipitation, ion exchange, commercial activated carbon adsorption, etc often become cost-prohibitive, the adsorption of MB by abundantly available green pea peel (GPP: Pisum sativum) derived and acid-treated carbon (GPP-AC) has proved to be a cost-attractive option in the present study. The physicochemical and morphological characteristics of GPP-AC were examined with the help of XRD, BET surface area, SEM, and Fourier transform infrared spectrophotometry ((FT-IR) analysis. The influences of such adsorption parameters as initial dye concentration, pH, contact time, adsorbent dosage, agitation speed, particle size, and temperature were evaluated and optimized. The equilibrium contact time for maximum adsorption of MB on to GPPAC was found to be 7 h. The equilibrium data of the adsorption process were modeled by using the Langmuir, Freundlich, Temkin, and Dubinin-Raduskevich (D-R) isotherms. However, the adsorption equilibrium data were best described by the Langmuir Isotherm model, with a maximum adsorption capacity of 163.94 mg MB/g GPPAC at 30°C.     

Production and comparison of high surface area bamboo derived active carbons

High surface area activated carbons have been produced from the natural biomaterial bamboo, using phosphoric acid as the activating agent. The effects of phosphoric acid impregnation ratio, activation temperature, heating rate on the carbon surface area, porosity and mass yield are presented. Three of these bamboo derived active carbons, surface areas 1337, 1628 and 2123m(2)/g were assessed for their ability to adsorb Acid Red 18 dye from aqueous solution; these results were compared with three conventional adsorbents: activated carbon F400, bone char and peat. Isotherm data were analysed using Langmuir, Freundlich, Redlich-Peterson and Langmuir-Freundlich isotherms. Different isotherms provided the best fit correlations to the adsorption experimental data but the Langmuir-Freundlich equation provided the best overall correlation of data. The adsorption capacities of two of the selected bamboo derived carbons were much greater than the capacities of the other three adsorbents.     

Enhancing of erythromycin production by <Emphasis Type="Italic">Saccharopolyspora erythraea</Emphasis> with common and uncommon oils

The enhancing effect of various concentrations of 18 oils and a silicon antifoam agent on erythromycin production by Saccharopolyspora erythraea was evaluated in a complex medium containing soybean flour and dextrin as the main substrates. The oils used consisted of sunflower, pistachio, cottonseed, melon seed, water melon seed, lard, corn, olive, soybean, hazelnut, rapeseed, sesame, shark, safflower, coconut, walnut, black cherry kernel and grape seed oils. The biomass, erythromycin, dextrin and oil concentrations and the pH value were measured. Also, the kinds and frequencies of fatty acids in the oils were determined. The productivity of erythromycin in the oil-containing media was higher than that of the control medium. However, oil was not suitable as a main carbon source for erythromycin production by S. erythraea. The highest titer of erythromycin was produced in medium containing 55 g/l black cherry kernel oil (4.5 g/l). The titers of erythromycin in the other media were also recorded, with this result: black cherry kernel > water melon seed > melon seed > walnut > rapeseed > soybean > (corn = sesame) > (olive = pistachio = lard = sunflower) > (hazelnut = cotton seed) > grape seed > (shark = safflower = coconut). In media containing various oils, the hyphae of S. erythraea were longer and remained in a vegetative form after 8 days, while in the control medium, spores were formed and hyphae were lysed.     

Sunflower seed oil and oleic acid utilization for the production of rhamnolipids by Thermus thermophilus HB8

The potential production of rhamnolipids was demonstrated using the thermophilic eubacterium Thermus thermophilus HB8 and sunflower seed oil or oleic acid as carbon sources. Sunflower seed oil was directly hydrolyzed by secretion of lipase and became a favorable carbon source for rhamnolipids production. Rhamnolipids levels were attainted high values, comparable to those produced by Pseudomonas strains from similar sources. Rhamnolipids synthesis in oleic acid exhibited a long period of induction, while in sunflower seed oil, the synthesis is more rapid. Glucose resulted in a more protracted period of rhamnolipids production after exhaustion of each or both carbon sources. Both mono- and di-rhamnolipids were identified by thin-layer chromatography (TLC) in the total rhamnolipids extract. The molecular composition of the produced biosurfactant was evaluated by Fourier transform infrared (FTIR) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and LC-MS analysis. Furthermore, secretion of rhamnolipids was confirmed on agar plates. The antimicrobial activity of rhamnolipids was detected against the bacterium Micrococcus lysodeikticus using a lysoplate assay. These results demonstrate that rhamnolipids produced in these substrates can be useful in both environmental and food industry applications by using cheap oil wastes. The alternative use of this thermophilic microorganism opens a new perspective concerning the valorization of wastes containing plant oils or frying oils to reduce the cost of rhamnolipids production.     

Activated carbon from char obtained from vacuum pyrolysis of teak sawdust: pore structure development and characterization

The preparation of activated carbon from vacuum pyrolysis char of teak sawdust was studied and the results are presented in this paper. The effects of process variables such as temperature and activation time on the pore structure of activated carbons were studied. The activated carbon prepared from char obtained by vacuum pyrolysis has higher surface area and pore volume than that from atmospheric pyrolysis char. The BET surface area and pore volume of activated carbon prepared from vacuum pyrolysis char were 1150 m2/g and 0.43 cm3/g, respectively.     

Microwave assisted thermal treatment of defective coffee beans press cake for the production of adsorbents

Defective coffee press cake, a residue from coffee oil biodiesel production, was evaluated as an adsorbent for removal of basic dyes (methylene blue – MB) from aqueous solutions. The adsorbent was prepared by microwave treatment, providing a significant reduction in processing time coupled to an increase in adsorption capacity in comparison to conventional carbonization in a muffle furnace. Batch adsorption tests were performed at 25 °C and the effects of particle size, contact time, adsorbent dosage and initial solution pH were investigated. Adsorption kinetics was better described by a second-order model. The experimental adsorption equilibrium data were fitted to Langmuir, Freundlich and Tempkin adsorption models, with Langmuir providing the best fit. The results presented in this study show that microwave activation presents great potential as an alternative method in the production of adsorbents.     

Preparation and characterization of activated carbon derived from the thermo-chemical conversion of chicken manure

Physico-chemical properties of a bioorganic char were modified by pyrolysis in the presence of NaOH, and with subsequent physical activation of carbonaceous species with CO2 a value-added activated carbon was fabricated. Bioorganic char is produced as a co-product during the production of bio-fuel from the pyrolysis of chicken litter. Untreated char contains approximately 37 wt% of C and approximately 43-45 wt% of inorganic minerals containing K, Ca, Fe, P, Cu, Mg, and Si. Carbonization and chemical activation of the char at 600 degrees C in the presence of NaOH in forming gas (4% H2 balanced with Ar) produced mainly demineralized activated carbon having BET (Brunauer, Emmett, and Teller) surface area of 486 m2/g and average pore size of 2.8 nm. Further physical activation with CO2 at 800 degrees C for 30 min resulted in activated carbon with BET surface area of 788 m2/g and average pore size of 2.2 nm. The mineral content was 10 wt%. X-ray photoelectron spectroscopy (XPS) indicated that the latter activation process reduced the pyrrolic- and/or pyridonic-N, increased pyridinic-N and formed quaternary-N at the expense of pyrrolic- and/or pyridonic-N found in the untreated char.     

DNA biosensor based on chitosan film doped with carbon nanotubes

A biosensor based on chitosan doped with carbon nanotube (CNT) was fabricated to detect salmon sperm DNA. Methylene blue (MB) was employed as a DNA indicator. It was found that CNTs can enhance the electroactive surface area threefold (0.28 +/- 0.03 and 0.093 +/- 0.06 cm(2) for chitosan-CNT- and chitosan-modified electrodes, respectively) and can accelerate the rate of electron transfer between the redox-active MB and the electrode. A low detection limit of 0.252 nM fish sperm DNA was achieved, and no interference was found in the presence of 5 microg/ml human serum albumin. The differential pulse voltammetry signal of MB was linear over the fish sperm DNA concentration range of 0.5-20 nM.