Activated carbons from flax shive and cotton gin waste as environmental adsorbents for the chlorinated hydrocarbon trichloroethylene

Agricultural by-products represent a considerable quantity of harvested commodity crops. The use of by-products as precursors for the production of widely used adsorbents, such as activated carbons, may impart a value-added component of the overall biomass harvested. Our objective in this paper is to show that flax shive and cotton gin waste can serve as a precursor for activated carbon that can be used for adsorption of trichloroethylene (TCE) from both the liquid and gas phases. Testing was conducted on carbon activated with phosphoric acid or steam. The results show that activated carbon made from flax shive performed better than select commercial activated carbons, especially at higher TCE concentrations. The activation method employed had little effect on TCE adsorption in gas or vapor phase studies but liquid phase studies suggested that steam activation is slightly better than phosphoric acid activation. As expected, the capacity for the activated carbons depended on the fluid phase equilibrium concentration. At a fluid concentration of 2 mg of TCE/L of fluid, the capacity of the steam activated carbon made from flax shive was similar at 64 and 80 mg TCE/g of carbon for the vapor and liquid phases, respectively. Preliminary cost estimates suggest that the production costs of such carbons are $1.50 to $8.90 per kg, depending on activation method and precursor material; steam activation was significantly less expensive than phosphoric acid activation.     

Sugarcane bagasse derivative-based superabsorbent containing phosphate rock with water-fertilizer integration

To improve the water-fertilizer utilization ratio and mitigate the environmental contamination, an eco-friendly superabsorbent polymer (SPA), modified sugarcane bagasse/poly (acrylic acid) embedding phosphate rock (MSB/PAA/PHR), was prepared. Ammonia, phosphate rock (PHR) and KOH were admixed in the presence of acrylic acid to provide nitrogen (N), phosphorus (P) and potassium (K) nutrients, respectively. Impacts on water absorption capacity of the superabsorbent polymer (SAP) were investigated. The maximum swelling capacity in distilled water and 0.9wt.% (weight percent) NaCl solution reached 414gg(-1) and 55gg(-1) (water/prepared SAP), respectively. The available NPK contents of the combination system were 15.13mgg(-1), 6.93mgg(-1) and 52.05mgg(-1), respectively. Moreover, the release behaviors of NPK in the MSB/PAA/PHR were also studied. The results showed that the MSB/PAA/PHR has outstanding sustained-release plant nutrients property.     

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.     

Adsorption of volatile organic compounds by pecan shell- and almond shell-based granular activated carbons

The objective of this research was to determine the effectiveness of using pecan and almond shell-based granular activated carbons (GACs) in the adsorption of volatile organic compounds (VOCs) of health concern and known toxic compounds (such as bromo-dichloromethane, benzene, carbon tetrachloride, 1,1,1-trichloromethane, chloroform, and 1,1-dichloromethane) compared to the adsorption efficiency of commercially used carbons (such as Filtrasorb 200, Calgon GRC-20, and Waterlinks 206C AW) in simulated test medium. The pecan shell-based GACs were activated using steam, carbon dioxide or phosphoric acid. An almond shell-based GAC was activated with phosphoric acid. Our results indicated that steam- or carbon dioxide-activated pecan shell carbons were superior in total VOC adsorption to phosphoric acid-activated pecan shell or almond shell carbons, inferring that the method of activation selected for the preparation of activated carbons affected the adsorption of VOCs and hence are factors to be considered in any adsorption process. The steam-activated, pecan shell carbon adsorbed more total VOCs than the other experimental carbons and had an adsorption profile similar to the two coconut shell-based commercial carbons, but had greater adsorption than the coal-based commercial carbon. All the carbons studied adsorbed benzene more effectively than the other organics. Pecan shell, steam-activated and acid-activated GACs showed higher adsorption of 1,1,1-trichloroethane than the other carbons studied. Multivariate analysis was conducted to group experimental carbons and commercial carbons based on their physical, chemical, and adsorptive properties. The results of the analysis conclude that steam-activated and acid-activated pecan shell carbons clustered together with coal-based and coconut shell-based commercial carbons, thus inferring that these experimental carbons could potentially be used as alternative sources for VOC adsorption in an aqueous environment.     

Effects of manufacturing conditions on the adsorption capacity of heavy metal ions by Makino bamboo charcoal

The objective of this study was to investigate the effects of manufacturing conditions on the adsorption capacity of heavy metal ions by Makino bamboo charcoal. Results show that the specific surface area and iodine number of bamboo charcoal activated at 900 degrees C were larger than those of bamboo charcoal activated at 800 degrees C. The specific surface area of bamboo charcoal activated at 800 degrees C by carbon dioxide was larger than that of charcoal activated by steam. However, a contrary result was observed when the activation temperature was 900 degrees C. The total volume and proportion of micropores in bamboo charcoal activated by carbon dioxide were greater than those in the other sample groups. However, the total volume and bulk volume of meso- and macropores, and average pore diameter for bamboo charcoal activated by steam were greater than those in the other sample groups. Using 5g bamboo charcoal (10-30 mesh) with a soaking time of 24h, a better adsorption effect on Pb2+ (100%), Cu2+ (100%), and Cr3+ (88-98%) was found. However, medium frequencies were observed for the adsorption of Cd2+ (40-80%) and Ni2+ (20-60%). Very limited adsorption of As5+ was detected in this study. For the same charcoal grain sizes, the adsorption capacity of 0.5g of charcoal was better than that of 0.1g. The improved adsorption effect of the sample group activated by steam was compared with the sample group activated by carbon dioxide.     

Adsorption of fluorobenzene onto granular activated carbon: isotherm and bioavailability studies

The adsorption of a recalcitrant fluoroaromatic compound, fluorobenzene (FB), onto granular activated carbon (GAC) was evaluated. The respective isotherm was obtained and the Langmuir, Freundlich and Redlich-Peterson models were fitted to the experimental data, with the Redlich-Peterson model giving the best fitting. Freundlich model also provided a good fit but the Langmuir model could not adequately fit the experimental data, especially at high FB concentrations. Maximal adsorption capacity of FB onto GAC was found to be 388mg of FB per gram of GAC. The reversibility of the adsorption of FB onto GAC was investigated, both in the absence and presence of microorganisms. Abiotic desorption of FB occurred to a small extent (between 3% and 22%, for amounts of FB initially adsorbed to the GAC between 37 and 388mgg(-1)), and bioregeneration of GAC was shown to occur when the matrix was exposed to a FB degrading culture, with 58-80% of the adsorbed FB being biodegraded. A residual amount of FB showed not to be bioavailable, suggesting that part of the adsorbed FB may be irreversibly bound. The fraction of the non-bioavailable FB increased at higher amounts of adsorbed FB, from 19% to 33%. The results indicate that the GAC employed in this study has a good capacity to adsorb FB and that bioregeneration of this matrix is a feasible process.     

Adsorptive removal of Pb(II) by activated carbon prepared from Spartina alterniflora: Equilibrium,kinetics and thermodynamics

Low-cost activated carbon was prepared from Spartina alterniflora by phosphoric acid activation for the removal of Pb(II) from dilute aqueous solution. The effect of experimental parameters such as pH, initial concentration, contact time and temperature on the adsorption was studied. The obtained data were fitted with the Langmuir and Freundlich equations to describe the equilibrium isotherms. The kinetic data were fitted with the Lagergren-first-order, pseudo-second-order and Elovich models. It was found that pH played a major role in the adsorption process. The maximum adsorption capacity for Pb(II) on S. alterniflora activated carbon (SAAC) calculated from Langmuir isotherm was more than 99 mg g⁻¹. The optimum pH range for the removal of Pb(II) was 4.8–5.6. The Freundlich isotherm model was found to best describe the experimental data. The kinetic rates were best fitted to the pseudo-second-order model. Thermodynamic study showed the adsorption was a spontaneous exothermic process.     

Coupled lactic acid fermentation and adsorption

Polyvinylpyridine (PVP) and activated carbon were evaluated for coupled lactic acid fermentation and adsorption, to prevent the product concentration from reaching inhibitory levels. The lactic acid production doubled as a result of periodical circulation of the fermentation broth through a PVP adsorption column. The adsorbent was then regenerated and the adsorbed lactate harvested, by passing 0.1 N NaOH through the column. However, each adsorption-regeneration cycle caused about 14% loss of the adsorption capacity, thus limiting the practical use of this rather expensive adsorbent. Activated carbon was found much more effective than PVP in lactic acid and lactate adsorption. The cells of Lactobacillus delbrueckii subsp. delbrueckii (LDD) also had strong tendency to adsorb on the carbon. A study was therefore conducted using an activated carbon column for simultaneous cell immobilization and lactate adsorption, in a semi-batch process with periodical medium replacement. The process produced lactate steadily at about 1.3 g l(-1)h(-1) when the replacement medium contained at least 2 g l(-1) of yeast extract. The production, however, stopped after switching to a medium without yeast extract. Active lactic acid production by LDD appeared to require yeast extract above a certain critical level (<2 g l(-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.     

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.     

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.     

Development of mesoporosity during phosphoric acid activation of wood in steam atmosphere

Oak and birch were used as precursors to produce the activated carbons (ACs) with well-developed mesoporosity by phosphoric acid-promoted activation in a steam atmosphere. The effect of experimental variables such as the amount of activating agent, the soaking time and the type of wood on the development of porous structure upon heating at 480 degrees C was investigated. The materials were characterized by N2 adsorption at 77K, mercury porosimetry and elemental analysis. It was demonstrated that increasing impregnation ratio favors the development of micropores and small mesopores of 2-5nm, whereas the soaking time promotes the creation of large mesopores, between 10 and 50nm. Compared to birch, the oak activation using phosphoric acid in the same conditions gives ACs with lower mesopore volume and higher contribution of small mesopores that reflects the differences between both precursors in their biopolymer composition. The presence of steam in the H3PO4 activation process compared to nitrogen facilitates the development of mesoporosity to much higher extent for the birch than that of oak. The ACs prepared in this work show the BET surface area ranging from 800 to 2250m2g(-1), the total pore volume of 0.35-2.04cm3g(-1) with mesopore fraction between 0.06 and 0.68.     

Arundo donax cane as a precursor for activated carbons preparation by phosphoric acid activation

Canes from Arundo donax, a herbaceous rapid-growing plant, were used as precursor for activated carbon preparation by phosphoric acid activation under a self-generated atmosphere. The influence of the carbonization temperature in the range 400-550 degrees C and of the weight ratio phosphoric acid to precursor (R = 1.5-2.5) on the developed porous structure of the resulting carbons was studied for 1 h of carbonization time. Surface properties of the activated carbons were dependent on a combined effect of the conditions employed. Carbons developed either with R = 1.5 over the range 400-500 degrees C, or with R = 2 at 500 degrees C exhibited surface areas of around 1100 m2/g, the latter conditions promoting a larger pore volume and enhanced mesoporous character. For both ratios, temperature above 500 degrees C led to reduction in porosity development. A similar effect was found for the highest ratio (R = 2.5) and 500 degrees C. The influence of carrying out the carbonization either for times shorter than 1 h or under flowing N2 was also examined at selected conditions (R = 2, 500 degrees C). Shorter times induced increase in the surface area (approximately 1300 m2/g), yielding carbons with smaller mean pore radius. Activated carbons obtained under flowing N2 possessed predominant microporous structures and larger ash contents than the samples derived in the self-generated atmosphere.     

Adsorption of heavy metal ions from aqueous solutions by activated carbon prepared from apricot stone

Apricot stones were carbonised and activated after treatment with sulphuric acid (1:1) at 200 degrees C for 24 h. The ability of the activated carbon to remove Ni(II), Co(II), Cd(II), Cu(II), Pb(II), Cr(III) and Cr(VI) ions from aqueous solutions by adsorption was investigated. Batch adsorption experiments were conducted to observe the effect of pH (1-6) on the activated carbon. The adsorptions of these metals were found to be dependent on solution pH. Highest adsorption occurred at 1-2 for Cr(VI) and 3-6 for the rest of the metal ions, respectively. Adsorption capacities for the metal ions were obtained in the descending order of Cr(VI) > Cd(II) > Co(II) > Cr(III) > Ni(II) > Cu(II) > Pb(II) for the activated carbon prepared from apricot stone (ASAC).     

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.     

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.     

Chlorella sorokiniana immobilized on the biomatrix of vegetable sponge of Luffa cylindrica: a new system to remove cadmium from contaminated aqueous medium

A new sorption system of microalgal cells immobilized on the biostructural matrix of Luffa cylindrica for sequestering cadmium is reported. Free and immobilized Chlorella sorokiniana removed cadmium from 10 mgl(-1) solution at the efficiency of 92.7% and 97.9% respectively. Maximum cadmium sorption was observed to be 39.2 mgg(-1) at equilibrium (C(eq)) of 112.8 mgl(-1) by immobilized microalgal biomass as compared to 33.5 mgg(-1) at C(eq) of 116.5 mgl(-1) by free biomass from initial concentration of 150 mgl(-1). In continuous liquid flow column, the cadmium sorption capacity of immobilized C. sorokiniana was 192 mgg(-1), which was 73.2% of the total metal passed in 51.5 l. Metal desorption with 0.1 M HCl was 100% and the desorbed immobilized system was reusable with a similar efficiency in the subsequent cycle.     

Enhanced adsorption of phenolic compounds, commonly encountered in olive mill wastewaters, on olive husk derived activated carbons

Olive husk was used for the preparation of activated carbon by chemical activation with KOH. The effects of carbonization and activation time on carbon properties were evaluated. The surface area of the produced carbons was measured by means of N(2) adsorption at 77K. The carbons with the highest surface area were further characterized by means of elemental analysis, particle size measurement, Boehm titration, zeta potential measurement, and temperature programmed desorption (TPD). Subsequently they were used for adsorption of a mixture of polyphenols consisting of caffeic acid, vanillin, vanillic acid, pi-hydroxybenzoic acid and gallic acid at two temperatures, and their adsorptive capacity was compared to a commercial carbon Acticarbon CX and found to be higher enough. The role of the porosity and surface groups are discussed in relation to the adsorption forces and the properties of the adsorbed substances. A thermodynamic interpretation of the results is also attempted.     

Copper removal by algae Gelidium, agar extraction algal waste and granulated algal waste: kinetics and equilibrium

Biosorption of copper ions by an industrial algal waste, from agar extraction industry has been studied in a batch system. This biosorbent was compared with the algae Gelidium itself, which is the raw material for agar extraction, and the industrial waste immobilized with polyacrylonitrile (composite material). The effects of contact time, pH, ionic strength (IS) and temperature on the biosorption process have been studied. Equilibrium data follow both Langmuir and Langmuir-Freundlich models. The parameters of Langmuir equilibrium model were: q(max)=33.0mgg(-1), K(L)=0.015mgl(-1); q(max)=16.7mgg(-1), K(L)=0.028mgl(-1) and q(max)=10.3mgg(-1), K(L)=0.160mgl(-1) respectively for Gelidium, algal waste and composite material at pH=5.3, T=20 degrees C and IS=0.001M. Increasing the pH, the number of deprotonated active sites increases and so the uptake capacity of copper ions. In the case of high ionic strengths, the contribution of the electrostatic component to the overall binding decreases, and so the uptake capacity. The temperature has little influence on the uptake capacity principally for low equilibrium copper concentrations. Changes in standard enthalpy, Gibbs energy and entropy during biosorption were determined. Kinetic data at different solution pH (3, 4 and 5.3) were fitted to pseudo-first-order and pseudo-second-order models. The adsorptive behaviour of biosorbent particles was modelled using a batch reactor mass transfer kinetic model, which successfully predicts Cu(II) concentration profiles.     

Generalized Mechanochemical Synthesis of Biomass‐Derived Sustainable Carbons for High Performance CO2 Storage

Novel mechanochemical activation generates biomass‐derived carbons with unprecedented CO₂ storage capacity due to higher porosity than analogous conventionally activated carbons but similar pore size. The mechanochemical activation, or so‐called compactivation, process involves compression, at 740 MPa, of mixtures of activating agent (KOH) and biomass hydrochar into pellets/disks prior to thermal activation. Despite the increase in surface area and pore volume of between 25% and 75% compared to conventionally activated carbons, virtually all of the porosity of the biomass (sawdust and lignin) derived mechanochemically activated carbons is from small micropores (5.8–6.5 Å), which results in a dramatic increase in CO₂ storage capacity at 25 °C and low pressure (≤1 bar). The ambient temperature CO₂ uptake for a carbon derived from sawdust at 600 °C and a KOH/carbon ratio of 2, rises from 1.3 to 2.0 mmol g^?1 at 0.15 bar, and from 4.3 to 5.8 mmol g^?1 at 1 bar, which is the highest ever reported for carbonaceous materials. The mechanochemically activated carbons have a superior CO₂ working capacity for pressure swing adsorption and vacuum swing adsorption processes and, due to a high packing density, they exhibit excellent volumetric CO₂ uptake that is higher than for any material reported to date.