Modification of water absorption capacity of a plastic based on bean protein using gamma irradiated starches as additives

Some properties of a bean protein–starch plastic were modified by irradiation of the starch. Two kinds of starch from bean and cassava were irradiated with doses until 50 kGy before their inclusion in the composite. Water absorption of the resultant product was reduced by 36% and 60% in materials containing bean and cassava starch, respectively. A large decline in the elongation is observed till 10 kGy in both materials, while tensile strength diminished by 11% in the cassava composite.     

Copper supported on porous activated carbon obtained by wetness impregnation: Effect of preparation conditions on the ozonation catalyst's characteristics

An activated carbon-supported copper heterogeneous catalyst based on (Cu/AC) was developed using a wetness impregnation process. The effect of preparation conditions on the catalyst's characteristics was examined. This work focuses on two key parameters: impregnation rate and calcination conditions (temperature and time). Catalysts were characterized by means of nitrogen sorptiometry at 77 K, Boehm analysis and pH_pzc analysis. It was found that the catalyst properties and the functional surface groups were affected by the operating conditions. The highest measured surface area, i.e. 1040 m²/g, was obtained for activated carbon (AC) impregnated with 12% of Cu loading after calcination at 550 °C for 2 h. The effect of adding copper on the surface of activated carbon on its adsorption capacity was also examined. The obtained results showed that after impregnation, the adsorption capacity of activated carbon was improved. Additionally, the performance of the Cu/AC catalyst on nitrobenzene ozonation was investigated. Our results show that the use of Cu/AC for heterogeneous catalytic ozonation enhanced significantly the degradation efficiency of nitrobenzene (NB) compared with simple ozonation and with ozonation catalyzed by AC without metal addition.     

Preparation of metal adsorbent from poly(methyl acrylate)-grafted-cassava starch via gamma irradiation

Metal adsorbent containing hydroxamic acid groups was successfully synthesized by radiation-induced graft copolymerization of methyl acrylate (MA) onto cassava starch. The optimum conditions for grafting were studied in terms of % degree of grafting (Dg). Conversion of the ester groups present in poly(methyl acrylate)-grafted-cassava starch copolymer into hydroxamic acid was carried out by treatment with hydroxylamine (HA) in the presence of alkaline solution. The maximum percentage conversion of the ester groups of the grafted copolymer, % Dg=191 (7.63 mmol/g of MA), into the hydroxamic groups was 70% (5.35 mmol/g of MA) at the optimum condition. The adsorbent of 191%Dg had total adsorption capacities of 2.6, 1.46, 1.36, 1.15 and 1.6 mmol/g-adsorbent for Cd²⁺, Al³⁺, UO₂²⁺, V⁵⁺ and Pb²⁺, respectively, in the batch mode adsorption.     

Production of activated carbon from sludge of food processing industry under controlled pyrolysis and its application for methylene blue removal

The present work aims to conduct a process optimization for the production of activated carbon from sludge of food processing industry. The significant feature of this sludge based activated carbon that makes it unique and economic is that it can be produced from waste material. The carbonaceous nature of this sludge does not allow its direct disposal to land because of excess organic and nutrient load contents, however, can be converted to a value added product. This process not only eliminates the need for further treatment of sludge but also reduce the cost of its handling, land filling, and transportation as well as the utilization in the same industry in the purification system.In the present work, activated carbon produced from pyrolysis of sludge was chemically activated by various activating agents. Optimization of impregnation ratio, impregnation time, activation temperature, and activation time was studied. The product was characterized through its iodine value and yield percentage. It was observed that the product had maximum iodine value of 624 mg g⁻¹ with ZnCl₂ as an activating agent. The FT-IR analysis depicts the presence of a variety of functional groups attached on the surface of activated carbon which are used in the interaction with the adsorbate during the process of adsorption. The XRD analysis reveals that the produced activated carbon has low content of inorganic constituents compared with the precursor. The product formed was applied for methylene blue adsorption. The adsorption equilibrium of methylene blue dye was examined at room temperature. Adsorption isotherm was drawn by applying Langmuir and Freundlich models fitting the data indict, with an adsorption capacity of 23.6 mg g⁻¹ and 14.2 mg g⁻¹, respectively. The data show that methylene blue adsorption is best suited to Langmuir equation.     

Adsorption of anthracene using activated carbon and Posidonia oceanica

The aim of this work was to examine the static capacity of adsorption of anthracene by Posidonia oceanica and activated carbon. The effect of experimental parameters pH and contact time on the anthracene adsorption onto cited materials was investigated in detail. The results showed that the anthracene removal on both P. oceanica and activated carbon was unaffected in the pH range of 2–12. The equilibrium data fit well to the Langmuir model with a maximum adsorption capacity of 8.35 mg/g and 0.14 mg/g, respectively with activated carbon and P. oceanica.     

Evaluation of an activated carbon from olive stones used as an adsorbent for heavy metal removal from aqueous phases

The performance of a microporous activated carbon prepared chemically from olive stones for removing Cu(II), Cd(II) and Pb(II) from single and binary aqueous solutions was investigated via the batch technique. The activated carbon sample was characterized using N₂ adsorption–desorption isotherms, SEM, XRD, FTIR, and Boehm titration. The effect of initial pH and contact time were studied. Adsorption kinetic rates were found to be fast and kinetic experimental data fitted very well the pseudo-second-order equation. The adsorption isotherms fit the Redlich–Peterson model very well and maximum adsorption amounts of single metal ions solutions follow the trend Pb(II) > Cd(II) > Cu(II). The adsorption behavior of binary solution systems shows a relatively high affinity to Cu(II) at the activated carbon surface of the mixture with Cd(II) or Pb(II). An antagonistic competitive adsorption phenomenon was observed. Desorption experiments indicated that about 59.5% of Cu(II) and 23% of Cd(II) were desorbed using a diluted sulfuric acid solution.     

Preparation and characterization of nanocomposite,silica aerogel,activated carbon and its adsorption properties for Cd (II) ions from aqueous solution

A novel composite adsorbent, silica aerogel activated carbon was synthesized by sol-gel process at ambient pressure drying method. The composite was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Nitrogen adsorption/desorption isotherms (BET).In the present study, the mentioned adsorbent was used moderately for the removal of cadmium ions from aqueous solutions and was compared with two other adsorbents of cadmium, activated carbon and silica aerogel. The experiments of Cd adsorption by adsorbents were performed at different initial ion concentrations, pH of the solution, adsorption temperature, adsorbent dosage and contact time. Moreover, the optimum pH for the adsorption was found to be 6.0 with the corresponding adsorbent dosage level of 0.1 g at 60 °C temperature. Subsequently, the equilibrium was achieved for Cd with 120 min of contact time.Consequently, the results show that using this composite adsorbent could remove more than 60% of Cd under optimum experimental conditions. Langmuir and Freundlich isotherm model was applied to analyze the data, in which the adsorption equilibrium data were correlated well with the Freundlich isotherm model and the equilibrium adsorption capacity (q_e) was found to be 0.384 mg/g in the 3 mg/L solution of cadmium.     

Effects of pyrolysis conditions on the physical characteristics of oil-palm-shell activated carbons used in aqueous phase phenol adsorption

Oil-palm shells, a biomass by-product from palm-oil mills, were converted into activated carbons by vacuum or nitrogen pyrolysis, followed by steam activation. The effects of pyrolysis environment, temperature and hold time on the physical characteristics of the activated carbons were studied. The optimum pyrolysis conditions for preparing activated carbons for obtaining high pore surface area are vacuum pyrolysis at a pyrolysis temperature of 675 °C and 2 h hold time. The activation conditions were fixed at a temperature of 900 °C and 1 h hold time. The activated carbons thus obtained possessed well-developed porosities, predominantly microporosities. For the pyrolysis atmosphere, it was found that significant improvement in the surface characteristics of the activated carbons was obtained for those pyrolysed under vacuum. Adsorption capacities of activated carbons were determined using phenol solution. For the activated carbons pyrolysed under optimum vacuum conditions, a maximum phenol adsorption capacity of 166 mg/g of carbon was obtained. A linear relationship between the BET surface area and the adsorptive capacity was shown.     

Electron beam combined with hydrothermal treatment for enhancing the enzymatic convertibility of sugarcane bagasse

The use of microbial cellulolytic enzymes is the most efficient process to liberate glucose from cellulose in biomass without the formation of fermentation inhibitors. A combination of pretreatment technologies is an alternative way to increase the access of enzymes to cellulose, and consequently, the conversion yield. In this way, the present study reports on the enzymatic hydrolysis of SCB submitted to three kinds of pretreatment: electron beam processing (EBP), and EBP followed by hydrothermal (TH) and diluted acid (AH) treatment. SCB samples were irradiated using a radiation dynamics electron beam accelerator, and then submitted to thermal and acid (0.1% sulfuric acid) hydrolysis for 40 and 60 min at 180 °C. These samples were submitted to enzymatic hydrolysis (EH) using commercial preparations, including Celluclast 1.5 L and beta-glycosidase. The addition of diluted acid improved TH treatment allowing for a shorter application time. EBP with 50 kGy increased the enzymatic hydrolysis yield of cellulose by 20% after TH and 30% after AH.     

Activated carbon prepared by physical activation of olive stones for the removal of NO2 at ambient temperature

Activated carbon was prepared from olive stones by physical activation using water vapor at 750 °C. Textural, morphology and surface chemistry characterizations were achieved (nitrogen adsorption, SEM, FTIR and TPD–MS). NO₂ adsorption was performed for different inlet gas compositions and temperatures. NO₂ may adsorb directly on the oxygenated surface groups, and can also be reduced to NO. Therefore, a second NO₂ molecule adsorbs on the oxygen left on the carbon surface. TPD performed after NO₂ adsorption showed the presence of various surface groups. The adsorption capacity was about 131 mg/g, which is higher than with several activated carbon prepared from classical lignocellulosic biomass. NO₂ reduction into NO decreased with increasing the inlet oxygen concentration. In contrast, a slight decrease in the NO₂ adsorption capacity was observed with increasing temperature. It seems that the activated carbons prepared from olive stones by steam activation could be used as efficient adsorbents for NO₂ removal.     

Synthesis of arsenic graft adsorbents in pilot scale

Synthesis of arsenic (As) adsorbents in pilot scale was carried out with a synthesizing apparatus by radiation-induced graft polymerization of 2-hydroxyethyl methacrylate phosphoric acid monomer (PA), which consists of phosphoric acid mono- (50%) and di- (50%) ethyl methacrylate esters onto a nonwoven cotton fabric (NCF), and following chemical modification by contact with a zirconium (Zr) solution. The apparatus which was equipped with reaction tanks, a washing tank and a pump can produce up to 0.3 m×14 m size of the As(V) adsorbent in one reaction. A degree of grafting of 150% was obtained at an irradiation dose of 20 kGy with 5% of PA solution mixed with deionized water for 1 h at 40 °C. Finally, after Zr(IV) was loaded onto a NCF with 5 mmol/L of Zr(IV) solution, the graft adsorbent for the removal of As(V) was achieved in pilot-scale. The adsorbent which was synthesized in pilot scale was evaluated in batch mode adsorption with 1 ppm (mg/l) of As(V) solution for 2 h at room temperature. As a result, the adsorption capacity for As(V) was 0.02 mmol/g-adsorbent.     

Refinery of Biomass by Utilization of Specific Effects of Microwave Irradiation

The results of application of microwave (MW) irradiation to achieve refinery of various kinds of recalcitrant biomass were summarized with special emphasis on recent innovative utilization of sensitizers for MW irradiation. The saccharification rates of lignocellulosic plant biomass consisting of softwoods, hardwoods and monocotyledons attained by the simple MW irradiation treatment were in the orders of 35-65% (softwoods), 70-80% (hardwoods) and around 80% (monocotyledons), respectively. The corresponding values of cellulose were around 69-81% (230-240 °C), while xylan was susceptible to the MW energy and easily decomposed into oligomers including xylose by heating at >150 °C, optimally at 204 °C, to give 99% solubility rate. However, the effects of the MW treatment on the agro-food byproducts varied highly depending upon their origins. These results indicate necessity of troublesome specification of the optimum condition for each case. For development of more versatile and comprehensive refinery method we tried to use sensitizers for MW irradiation.We found that hydrogen peroxide was remarkably effective for biomass refinery. Utilization of activated carbon as a sensitizer for MW irradiation was also effective for saccharification of starchy materials. Enhancement of the surface charge of the activated carbons by oxidation and preparation of microwave absorption solid acid catalysts were recommended to further enhance their effectiveness. The overall results showed the importance of four factors, less affinity toward oligosaccharides in relation with pore size, quantity of surface negative charges in addition to electro-conductivity, faster filtration ability and unknown hot spot productivity. Due to removal of the coloured materials by the activated carbons, clear saccharified solution produced by one pot conversion could be directly used for further fermentation to produce biofuels such as ethanol.     

Valorization of two waste streams into activated carbon and studying its adsorption kinetics,equilibrium isotherms and thermodynamics for methylene blue removal

Wastes must be managed properly to avoid negative impacts that may result. Open burning of waste causes air pollution which is particularly hazardous. Flies, mosquitoes and rats are major problems in poorly managed surroundings. Uncollected wastes often cause unsanitary conditions and hinder the efforts to keep streets and open spaces in a clean and attractive condition. During final disposal methane is generated, it is much more effective than carbon dioxide as a greenhouse gas, leading to climate change. Therefore, this study describes the possible valorization of two waste streams into activated carbon (AC) with added value due to copyrolysis. High efficiency activated carbon was prepared by the copyrolysis of palm stem waste and lubricating oil waste. The effects of the lubricating oil waste to palm stem ratio and the carbonization temperature on the yield and adsorption capacity of the activated carbon were investigated. The results indicated that the carbon yield depended strongly on both the carbonization temperature and the lubricating oil to palm stem ratio. The efficiency of the adsorption of methylene blue (MB) onto the prepared carbons increased when the lubricating oil to palm stem ratio increased due to synergistic effect. The effects of pH, contact time, and the initial adsorbate concentration on the adsorption of methylene blue were investigated. The maximum adsorption capacity (128.89 mg/g) of MB occurred at pH 8.0. The MB adsorption kinetics were analyzed using pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models. The results indicated that the adsorption of MB onto activated carbon is best described using a second order kinetic model. Adsorption data are well fitted with Langmuir and Freundlich isotherms. The thermodynamic parameters; ΔG°, ΔH° and ΔS° indicate that the adsorption is spontaneous and endothermic.     

Preparation of active carbons from corn stalk for butanol vapor adsorption

Active carbons(ACs) were prepared through chemical activation of biochar from whole corn stalk(WCS)and corn stalk pith(CSP) at varying temperatures using potassium hydroxide as the activating agent. ACs were characterized via pore structural analysis and scanning electron microscopy(SEM). These adsorbents were then assessed for their adsorption capacity for butanol vapor. It was found that WCS activated at900 °C for 1 h(WCS-900) had optimal butanol adsorption characteristics. The BET surface area and total pore volume of the WCS-900 were 2330 m2/g and 1.29 cm3/g, respectively. The dynamic adsorption capacity of butanol vapor was 410.0 mg/g, a 185.1% increase compared to charcoal-based commercial AC(143.8 mg/g).     

Adsorption of eicosane and 1,2-hexanediol from supercritical carbon dioxide on activated carbon and chromosorb

Supercritical adsorption isotherms were measured for eicosane and 1,2-hexanediol on activated carbon and chromosorb 101 at 324.2 K and 11.45 MPa. Adsorption isotherms of both solutes on activated carbon have typical shapes and can be modelled by Langmuir or Freundlich equations. For chromosorb 101 the equilibrium loadings are a linear function of the concentration of the solute in the fluid phase. These results suggest that for chromosorb 101 a partition of the solute between two immiscible phases rather than adsorption occurs.     

An insight into Faradaic phenomena in activated carbon investigated by means of the microelectrode technique

Cyclic voltammetry was performed on activated carbon particles in a microelectrode setup to investigate the behaviour of an activated carbon with oxygen functionalities. Quinoid type redox peaks were clearly seen in the potential region around −0.5 V vs. Hg/HgO. After polarization below −0.4 V, an anodic peak confirms previous studies using a pristine carbon, but in the present work much higher in intensity. In addition, a corresponding cathodic peak, not previously reported, was also found. The appearance of this pair of peaks in a functionalized carbon may be connected to reversible hydrogen adsorption together with Faradaic reactions involving oxygenated functional groups.     

Green Synthesis of Some Calix[4]Resorcinarene Under Microwave Irradiation

A green synthetic procedure for the preparation of some calix[4]resorcinarenes using a household microwave oven has been carried out. This method represents a very rapid heating alternative to the conventional method that involves very long time of reactions (from 20-24 h in conventional heating to 5-8 min in microwave irradiation). C-4-hydroxy–3-methoxycalix[4]resorcinarene (CHMPCR), C-4-methoxyphenylcalix[4]resorcinarene (CMPCR) and C-2–phenylethenilcalix[4]resorcinarene (CPECR) was achieved by placed of resorcinol, an aldehyde, HCl and ethanol inside a household microwave oven. The product was recrystallized by methanol and analyzed by spectral analysis (FTIR, H-NMR and MS). Optimization of reaction was carried out in variation of microwave power, reaction times and reactant composition. The result shows that optimum condition of synthesis of C-4-hydroxy-3–methoxycalix[4]resorcinarene (CHMPCR) with microwave irradiation were at microwave power 332 W, reaction time 8 min and the mole ratio of resorcinol and 4-hydroxy-3-methoxyphenylbenzaldehyde 1:1. This parameter gave product in 97.8% (53.7% after recrystallization). The CPECR synthesis using resorcinol and cynnamaldehyde (1:1) at microwave power 332 W for 5 min afforded the product in 97.3% (44.5% after recrystallization). Whereas the reaction of resorcinol and 4-methoxyphenylbenzaldehyde (1:1.2) at microwave power 264 W for 5 min gave CMPCR in 99.5% (68.6% after recrystallization).     

Macroporous chitin affinity membranes for wheat germ agglutinin purification from wheat germ

Macroporous chitin membranes of controlled porosity and pore sizes have been prepared. They have good mechanical properties and allow high flow rates of protein solutions at low pressure drops. Because of the numerous N-acetyl-D-glucosamine (GlcNAc) moieties they contain, the chitin membranes can be used for the separation of some valuable proteins both as affinity ligands and support matrix, without further modification. Due to their high porosity and high adsorption surface area, the chitin membranes provide a larger number of accessible binding sites for the wheat germ agglutinin than the chitin beads do. The adsorption capacity for wheat germ agglutinin (180 mg/g chitin membrane) is about 20 times larger than that of chitin beads. Because of the numerous binding sites, multiple-point bindings are involved in the protein adsorption. For this reason, a strong eluant, namely a 1 M acetic acid aqueous solution, had to be used to efficiently recover the wheat germ agglutinin from the membrane. The wheat germ agglutinin was extracted from wheat germ with 0.05 M HCl, precipitated with ammonium sulfate, dialyzed against 0.01 M Tris–HCl buffer (pH 8.5), and purified on the chitin membrane. A high purity (>99%) wheat germ agglutinin with high yield (∼50 mg/100 g wheat germ) was obtained.     

Adsorption of strontium from aqueous solution using activated carbon produced from textile sewage sludges

Different types of activated carbons were prepared by changing the activation temperatures (400–700 °C) and impregnation ratio (sewage sludge: KOH; 1:1, 1:2) and the removal of Sr⁺² from aqueous solution was determined. The maximum adsorption yield (12.11 mg/g) was obtained at 500 °C for 1 h carbonization conditions with impregnation ratio of 1:1. The affecting parameters were analyzed by using central composite design method. The selected parameters were initial pH, temperature, initial strontium concentration and carbon dosage. The analysis of variance was performed in 95% confidence level and checked to fitting of experimental value and predicted value. The significant F was P < 0.05 with a model F value of 19.94 which revealed that this regression is statistically significant. The results of regression analysis indicated that pH and temperature parameters were not individually statistically significant for Sr⁺²sorption. However, the efficiency of strontium sorption increases with the increase in carbon dosage and decreases with the Sr⁺² concentration. Influences of initial pH and temperature, pH and Sr⁺² concentration, temperature and carbon dosage and Sr⁺² concentration and carbon dosage on the adsorption process were considered statistically significant. Adsorption of strontium was described by Freundlich isotherm as a physical adsorption (E = 7.2 kJ/mol). The adsorption reactions were calculated as endothermic, spontaneous and favorable reactions.     

Poly(vinyl alcohol) separators improve the coulombic efficiency of activated carbon cathodes in microbial fuel cells

High-performance microbial fuel cell (MFC) air cathodes were constructed using a combination of inexpensive materials for the oxygen reduction cathode catalyst and the electrode separator. A poly(vinyl alcohol) (PVA)-based electrode separator enabled high coulombic efficiencies (CEs) in MFCs with activated carbon (AC) cathodes without significantly decreasing power output. MFCs with AC cathodes and PVA separators had CEs (43%–89%) about twice those of AC cathodes lacking a separator (17%–55%) or cathodes made with platinum supported on carbon catalyst (Pt/C) and carbon cloth (CE of 20%–50%). Similar maximum power densities were observed for AC-cathode MFCs with (840 ± 42 mW/m²) or without (860 ± 10 mW/m²) the PVA separator after 18 cycles (36 days). Compared to MFCs with Pt-based cathodes, the cost of the AC-based cathodes with PVA separators was substantially reduced. These results demonstrated that AC-based cathodes with PVA separators are an inexpensive alternative to expensive Pt-based cathodes for construction of larger-scale MFC reactors.