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.     

Thermal conversion of alkaline lignin and its structured derivatives to porous carbonized materials

Alkaline lignin was thermally converted to microporous carbon in ca. 50% yield by heating up from room temperature to 900 °C without activation process under flowing of an argon gas. The carbonized material prepared by heating up conditions of 1 °C min⁻¹ showed 530 m²/g of the Brunauer-Emmett-Teller (BET) specific surface area, which increased to 740 m²/g after washing with water. Furthermore, alkaline lignin derivatives were structured as micron scale particles by micelle formation and polymer gelation techniques. Carbonization of the structured lignins could afford high porous materials having BET surface areas above 1000 m²/g without surface activation processes.     

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.     

Performances of toluene removal by activated carbon derived from durian shell

In the effort to find alternative low cost adsorbent for volatile organic vapors has prompted this research in assessing the effectiveness of activated carbon produced from durian shell in removing toluene vapors. Durian shells were impregnated with different concentrations of H₃PO₄ followed by carbonization at 500 °C for 20 min under nitrogen atmosphere. The prepared durian shell activated carbon (DSAC) was characterized for its physical and chemical properties. The removal efficiency of toluene by DSAC was performed using different toluene concentrations. Results showed that the highest BET surface area of the produced DSAC was 1404 m²/g. Highest removal efficiency of toluene vapors was achieved by using DSAC impregnated with 30% of acid concentration heated at 500 °C for 20 min heating duration. However, there is insignificant difference between removal efficiency of toluene by DSAC and different toluene concentrations. The toluene adsorption by DSAC was better fitted into Freundlich model.     

Improved performance of membrane free single-chamber air-cathode microbial fuel cells with nitric acid and ethylenediamine surface modified activated carbon fiber felt anodes

Surface modifications of anode materials are important for enhancing power generation of microbial fuel cell (MFC). Membrane free single-chamber air-cathode MFCs, MFC-A and MFC-N, were constructed using activated carbon fiber felt (ACF) anodes treated by nitric acid and ethylenediamine (EDA), respectively. Experimental results showed that the start-up time to achieve the maximum voltages for the MFC-A and MFC-N was shortened by 45% and 51%, respectively as compared to that for MFC-AT equipped with an unmodified anode. Moreover, the power output of MFCs with modified anodes was significantly improved. In comparison with MFC-AT which had a maximum power density of 1304 mW/m², the MFC-N achieved a maximum power density of 1641 mW/m². The nitric acid-treated anode in MFC-A increased the power density by 58% reaching 2066 mW/m². XPS analysis of the treated and untreated anode materials indicated that the power enhancement was attributable to the changes of surface functional groups.     

Adsorption of Victoria blue by carbon/Ba/alginate beads: Kinetics,thermodynamics and isotherm studies

The kinetic, thermodynamic and isotherm modeling studies were carried out on adsorptive removal of Victoria blue (VB) dye using activated carbon, Ba/alginate and modified carbon/Ba/alginate polymer beads. The feasibility of sorption process was determined by varying the experimental parameters viz., dye concentration (4–20 mg L⁻¹), contact time (10–90 min), pH (3–10), adsorbent dose (0.5–2.5 g) and temperature (303–343 K). Freundlich and Langmuir isotherms were determined and ascertained with the dimensionless separation factor (R_L). Lagergren's pseudo-first order, pseudo-second order and intraparticle diffusion model equations were used to analyze the kinetics of the adsorption process. The thermodynamic consistency of adsorption was found with Gibbs free energy (ΔG°), changes in enthalpy (ΔH°) and entropy (ΔS°) were calculated using the Van’t Hoff plot. The polymer beads were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and their morphology was determined by scanning electron microscopy (SEM).     

Development of low-concentration mercury adsorbents from biohydrogen-generation agricultural residues using sulfur impregnation

Mercury adsorbents were derived from waste biohydrogen-generation barley husk and rice husk via carbonization, steam activation, and sulfur impregnation at 300-650 °C. The samples derived from agricultural residues showed a greater Hg⁰ adsorption than that of a coal-based activated carbon, confirming the feasibility of resource recovery of these agricultural residuals for low-concentration gaseous Hg adsorption. Sulfur impregnation reduced both the surface area and pore volume of the samples, with lower temperature causing a greater decrease. Elevating the impregnation temperature increased the organic sulfur contents, suggesting that in addition to elemental sulfur, organic sulfur may also act as active sites to improve Hg⁰ adsorption. Oxygen and sulfur functional groups accompanying the microporous structures may account for the enhancing Hg⁰ adsorption of the raw and sulfur-treated samples, respectively. The pseudo-second-order model can best describe the chemisorption characteristics, implying that Hg⁰ adsorption on the samples was in a bimolecular reaction form.     

Enhancement in current density and energy conversion efficiency of 3-dimensional MFC anodes using pre-enriched consortium and continuous supply of electron donors

Using a pre-enriched microbial consortium as the inoculum and continuous supply of carbon source, improvement in performance of a three-dimensional, flow-through MFC anode utilizing ferricyanide cathode was investigated. The power density increased from 170 W/m³ (1800 mW/m²) to 580 W/m³ (6130 mW/m²), when the carbon loading increased from 2.5 g/l-day to 50 g/l-day. The coulombic efficiency (CE) decreased from 90% to 23% with increasing carbon loading. The CEs are among the highest reported for glucose and lactate as the substrate with the maximum current density reaching 15.1 A/m². This suggests establishment of a very high performance exoelectrogenic microbial consortium at the anode. A maximum energy conversion efficiency of 54% was observed at a loading of 2.5 g/l-day. Biological characterization of the consortium showed presence of Burkholderiales and Rhodocyclales as the dominant members. Imaging of the biofilms revealed thinner biofilms compared to the inoculum MFC, but a 1.9-fold higher power density.     

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.     

Activated carbons from sisal waste by chemical activation with K₂CO₃: kinetics of paracetamol and ibuprofen removal from aqueous solution

Sisal waste was used as precursor to prepare carbons by chemical activation. The influence of the K₂CO₃ amount and activation temperature on the materials textural properties were studied through N₂ and CO₂ adsorption assays. As the severity of the treatment increases there is a development of supermicropores, and the micropore size distribution changes from mono to bimodal. A carbon with an apparent surface area of 1038 m² g⁻¹ and pore volume of 0.49 cm³ g⁻¹ was obtained. TPD results showed the incidence in acidic type groups although the pH_PZC reveals an almost neutral character of the surface. Adsorption kinetic data of ibuprofen and paracetamol show that the processes obey to a pseudo-second order kinetic equation. Regarding the removal efficiency the prepared samples attained values comparable to a commercial carbon (>65%), revealing that chemical activation of sisal wastes with K₂CO₃ allows obtaining samples suitable for pharmaceutical compounds removal from liquid phase.     

Phenol degradation by microorganisms adsorbed on activated carbon

Summary The phenol degradation by Candida sp. and Pseudomonas sp. immobilized on activated carbon was investigated. Thanks to its great adsorptive surface, activated carbon is suited as supporting material for microorganisms and also provides a high adsorption capacity for phenol.The immobilization by adsorption avoids any unphysiological treatment of the microorganisms. One gram activated carbon adsorbed in 10 h about 4×10⁹ Pseudomonas cells and 3×10⁸ Candida cells. While the free cells did not tolerate more than 1.5 g/l phenol, the adsorbed microorganisms survived at temporary high phenol concentrations up to 15 g/l, and they degraded about 90% of the adsorbed phenol.The activated carbon operated like a depot: the adsorbed phenol diffused out of the carbon and could be metabolized by the microorganisms. The results give an explanation of the stimulating effect of activated carbon in the treatment of waste waters observed until now.     

Study on activated carbon derived from sewage sludge for adsorption of gaseous formaldehyde

The aim of this work is to evaluate the adsorption performances of activated carbon derived from sewage sludge (ACSS) for gaseous formaldehyde removal compared with three commercial activated carbons (CACs) using self-designing adsorption and distillation system. Formaldehyde desorption of the activated carbons for regeneration was also studied using thermogravimetric (TG) analysis. The porous structure and surface characteristics were studied using N₂ adsorption and desorption isotherms, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results show that ACSS has excellent adsorption performance, which is overall superior to the CACs. Adsorption theory indicates that the ACSS outperforms the CACs due to its appropriate porous structure and surface chemistry characteristics for formaldehyde adsorption. The TG analysis of desorption shows that the optimum temperature to regenerate ACSS is 75 °C, which is affordable and economical for recycling.     

Cellulose esters from waste cotton fabric via conventional and microwave heating

The esterification of cellulose from waste cotton fabric in a N,N-dimethylacetamide/lithium chloride solvent system was carried out using different types of fatty acid chloride including butyryl chloride, capryloyl chloride, and lauroyl chloride as esterifying agents, and N,N-dimethyl 1-4-aminopyridine as a catalyst under conventional and microwave activation. Microwave esterification was performed under 2.45 GHz with power varying from 90 to 450 W. The optimum conditions for esterification of cotton cellulose with various esterifying agents were investigated in terms of reaction time and temperature to attain appropriate %weight increase and degree of substitution of esterified-cellulose. The degree of substitution, functional group and chemical structure, and thermal stability of cellulose ester powder were characterized by ¹H NMR, FTIR, and TGA/SDTA analysis. Morphologies, crystallinity, and solubility of modified cellulose by two different heating methods were compared.     

Synthesis of γ-cyclodextrin/chitosan composites for the efficient removal of Cd(II) from aqueous solution

The synthesis of chitosan-graft-γ-cyclodextrin (Ch-g-γ-CD) using persulfate/ascorbic acid redox system was done and characterized by FTIR, XRD, TGA and SEM/EDX. The optimum yield of the copolymer was obtained using 16 × 10⁻³ M γ-cyclodextrins (γ-CD), 2.8 × 10⁻² M ascorbic acid (AA), 1.8 × 10⁻² M K₂S₂O₈ and 0.1 g chitosan in 25 mL of 2% aqueous formic acid at 45 ± 0.2 °C. The highest percent grafting samples were evaluated for cadmium metal ion (Cd(II)) removal from the aqueous solutions where the sorption capacities were found proportional to the grafting extent. The sorption was pH and concentration dependent where, pH = 8.5 was found to be the optimum value. The adsorption data were modeled using Langmuir and Freundlich isotherms. The equilibrium data followed the Langmuir isotherm model with maximum sorption capacity of 833.33 mg/g. The influence of electrolytes, sodium chloride (NaCl) and sodium sulphate (Na₂SO₄) on Cd(II) uptake was also studied. Desorption of the cadmium loaded Ch-g-γ-CD was accomplished with 0.01 N H₂SO₄. The adsorbent exhibited high reusability and could be successfully recycled for nine cycles where in the ninth cycle 27% adsorption was feasible.     

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.     

Adsorption of Bovine Serum Albumin from salt solution onto activated carbon

One of the wastewaters from tanning industry (soak liquor) contains 0.4 g/l of dissolved protein. During coagulation and flocculation 41 % of protein was removed. A suggestion has been made to remove the residual protein by adsorption technique. The optimum conditions for adsorption of Bovine Serum Albumin (BSA) on rice bran based activated carbon (RBAC) have been determined. Maximum adsorption of BSA took place at pH 7.O. Ionic strength was found to have influence on the adsorption behaviour. Adsorption capacity of BSA onto charcoal surface decreased with increase in temperature. Enthalpy of adsorption in all cases was found to be within –19 to –57 kJ/mole, indicating exothermic nature of the process. Applicability of adsorption technique to the removal of dissolved protein from soak water has been studied. The maximum removal of protein occurred at pH 7.0 and the ratio of protein removed to weight of adsorbent was 3.22×10^–3 g/g.     

Optimization of microwave-assisted FeCl3 pretreatment conditions of rice straw and utilization of Trichoderma viride and Bacillus pumilus for production of reducing sugars

In this study, Box-Behnken design (BBD) and response surface methodology (RSM) were used to optimize microwave-assisted FeCl₃ pretreatment conditions of rice straw with respect to FeCl₃ concentration, microwave intensity, irradiation time and substrate concentration. When rice straw was pretreated at the optimal conditions of FeCl₃ concentration, 0.14 mol/L; microwave intensity, 160 °C; irradiation time, 19 min; substrate concentration, 109 g/L; and inoculated with Trichoderma viride and Bacillus pumilus, the production of reducing sugars was 6.62 g/L. This yield was 2.9 times higher than that obtained with untreated rice straw. The microorganisms degraded 37.8% of pretreated rice straw after 72 h. The structural characteristic analyses suggest that microwave-assisted FeCl₃ pretreatment damaged the silicified waxy surface of rice straw, disrupted almost all the ether linkages between lignin and carbohydrates, and removed lignin.     

Simultaneous activated carbon adsorption within a membrane bioreactor for an enhanced micropollutant removal

Significant adsorption of sulfamethoxazole and carbamazepine to powdered activated carbon (PAC) was confirmed by a series of adsorption tests. In contrast, adsorption of these micropollutants to the sludge was negligible. The removal of these compounds in membrane bioreactor (MBR) was dependent on their hydrophobicity and loading as well as the PAC dosage. Sulfamethoxazole exhibited better removal rate during operation under no or low (0.1 g/L) PAC dosage. When the PAC concentration in MBR was raised to 1.0 g/L, a sustainable and significantly improved performance in the removal of both compounds was observed - the removal efficiencies of sulfamethoxazole and carbamazepine increased to 82 ± 11% and 92 ± 15% from the levels of 64 ± 7%, and negligible removal, respectively. The higher removal efficiency of carbamazepine at high (1.0 g/L) PAC dosage could be attributed to the fact that carbamazepine is relatively more hydrophobic than sulfmethoxazole, which subsequently resulted in its higher adsorption affinity toward PAC.     

Treatment of biodiesel production wastes with simultaneous electricity generation using a single-chamber microbial fuel cell

Biodiesel production through transesterification of lipids generates large quantity of biodiesel waste (BW) containing mainly glycerin. BW can be treated in various ways including distillation to produce glycerin, use as substrate for fermentative propanediol production and discharge as wastes. This study examined microbial fuel cells (MFCs) to treat BW with simultaneous electricity generation. The maximum power density using BW was 487 ± 28 mW/m² cathode (1.5 A/m² cathode) with 50 mM phosphate buffer solution (PBS) as the electrolyte, which was comparable with 533 ± 14 mW/m² cathode obtained from MFCs fed with glycerin medium (COD 1400 mg/L). The power density increased from 778 ± 67 mW/m² cathode using carbon cloth to 1310 ± 15 mW/m² cathode using carbon brush as anode in 200 mM PBS electrolyte. The power density was further increased to 2110 ± 68 mW/m² cathode using the heat-treated carbon brush anode. Coulombic efficiencies (CEs) increased from 8.8 ± 0.6% with carbon cloth anode to 10.4 ± 0.9% and 18.7 ± 0.9% with carbon brush anode and heat-treated carbon brush anode, respectively.     

Evaluation of an integrated sponge--granular activated carbon fluidized bed bioreactor for treating primary treated sewage effluent

An integrated fluidized bed bioreactor (iFBBR) was designed to incorporate an aerobic sponge FBBR (ASB-FBBR) into an anoxic granular activated carbon FBBR (GAC-FBBR). This iFBBR was operated with and without adding a new starch based flocculant (NSBF) to treat synthetic primary treated sewage effluent (PTSE). The NSBF contains starch based cationic flocculants and trace nutrients. The results indicate that the iFBBR with NSBF addition could remove more than 93% dissolved organic carbon (DOC), 61% total nitrogen (T-N) and 60% total phosphorus (T-P) at just a very short hydraulic retention time of 50 min. The optimum frequency of adding NSBF to the iFFBR is four times per day. As a pretreatment to microfiltration, the iFFBR could increase 5 L/m² h of critical flux thus reducing the membrane fouling. In addition, better microbial activity was also observed with high DO consumption (>66%) and specific oxygen uptake rate (>35 mg O₂/g VSS h).