Boehm Titration Research Articles

Synergetic removal of hazardous pollutants from aqueous environment using lignocellulosic biosorbents

Water pollution with dyes that are non-biodegradable has become a very concerning environmental problem in the world today. Therefore, the aim of this research was to optimize an adsorption process for the removal of one of the most harmful dyes Eriochrome Black T (EBT). For the first time, native hazelnut shells were used as biosorbents in this regard. The biomaterial was analysed by infrared spectroscopy with Fourier transformation, scanning electron microscopy, electron dispersive spectroscopy, Boehm titrations, physicochemical analysis and by determination of zero charge point and cation exchange capacity. Dye concentration was established by UV–Vis spectrophotometer and heavy metals concentration by flame atomic absorption spectrometry (FAAS). Characterization techniques of EBT showed successful removal from wastewater due to the obvious changes in morphological and composition structure of the hazelnut shell. The highest capacity of adsorption (5.8 mg/g) and removal efficiency (75.3%) was found at pH 3, sorbent mass 500 mg, 80 mg/L EBT concentration, 90 min contact time and solution temperature 20 °C. The pseudo-second-order model described the best investigated process and maximum Langmuir’s adsorption capacity was 27.55 mg/g. The interfering effect of seven heavy metals increased removal efficiency to 98% showing a positive impact. Furthermore, the process was found feasible with negative values of Gibbs free energy and exothermic with negative values of enthalpy change (-35.26 kJ/mol). The utilized green and environmentally friendly sorbent under optimized conditions could be used in real textile industries for EBT and heavy metals removal.

Chemical oxygen demand removal by modified carbon with H2SO4 from oil palm fruit bunches

ABSTRACT The utilisation of biomass to be used as a promising material is essential to reduce environmental pollution. This study aims to determine the effect of adding a modifier to activated carbon from oil palm empty bunches. The material’s efficacy in reducing Chemical Oxygen Demand (COD) in the water environment was also conducted. In this research, the removal of COD was investigated using activated carbon from empty fruit bunches as a adsorbent with modification. The carbon synthesis of activated carbon was done by synthesising oil palm empty fruit bunches at 500 °C with activation using H3PO4 and surface modification with H2SO4. Modifying the activated carbon surface is expected to increase pores and clean the surface to optimise adsorption The activated and modified carbon were characterised using FTIR, SEM, XRD, and BET methods. The FTIR results show the absorption of functional groups indicating the presence of functional groups for C-H, O-H, C-O, C=C and C=O. The Boehm Titration method showed that total acid increased after modification. SEM analysis on samples shows that the sample surface is porous, and the number of pores produced is increasing. The XRD analysis result shows that the material revealed two broad diffractions at degree 2θ corresponding to the faces of porous carbon. The BET result showed that the material had a higher pore volume after the modification of activated carbon. The adsorption of modified carbon was higher than that of activated carbon. The optimum contact time for activated and modified activated carbon is 90 minutes and pH 2. The modified carbon from oil palm fruit bunches can reduce COD in a water environment.

Adsorption of Cobalt and Strontium Ions on Plant-Derived Activated Carbons: The Suggested Mechanisms

In this study, activated carbons derived from walnut shells (CA-N) and apple wood (CA-M) were used as adsorbents to remove cobalt(II) and strontium(II) ions from aqueous solutions. The novel materials were obtained using nitric acid (CA-Mox) and nitric acid/urea mixture (CA-Mox-u, CA-Nox-u) as oxidizing agents. The physical–chemical characteristics of activated carbons were determined from nitrogen sorption isotherms, SEM-EDX, FTIR, pH metric titrations, the Boehm titration method and elemental analysis. The results of batch experiments indicate that maximum adsorption can be achieved in broad pH ranges: 4–8 for Co(II) and 4–10 for Sr(II). The maximum adsorption capacities of Co(II) and Sr(II) on oxidized activated carbons at pH = 4 are: CA-Mox, 0.085 and 0.076 mmol/g; CA-Mox-u, 0.056 and 0.041 mmol/g; and CA-Nox-u, 0.041 and 0.034 mmol/g, respectively. The mathematical models (pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models, and Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin–Pyzhev isotherm models) were used to explain the adsorption kinetics, to study the adsorption mechanism and predict maximum adsorption capacity of the adsorbents. The adsorption mechanisms of toxic metal ions on activated carbons were proposed.

COPPER ADSORPTION ONTO POMEGRANATE PEEL ACTIVATED CARBON AS A NEW ADSORBENT

Pomegranate peel-based activated carbon was prepared using phosphoric acid impregnation for removing copper ions from aqueous solutions. The activated carbon sample was characterized using N2 adsorption–desorption isotherms, SEM, FTIR, and Boehm titration. Batch adsorption experiments were performed as a function of initial pH, contact time, initial ion concentration and temperature. The metal adsorption was found pH dependent, with maximum adsorption occurring at an initial pH of 5.4. Langmuir, Freundlich and Temkin isotherms were used to analyze the equilibrium data at different temperatures. The Freundlich isotherm was considered to be the best model for representing Cu(II) adsorption data. The kinetic studies were analyzed using pseudo-first order, pseudo-second order and intraparticle diffusion models, with good fitting to the pseudo-second-order model. The adsorption behavior of the binary solution system Cu(II)-Cd(II) showed that the adsorbent has higher selectivity towards copper ions than cadmium ions.

Tuning the Interlayer Distance of Graphene Oxide as a Function of the Oxidation Degree for o‐Toluidine Removal

AbstractGraphene oxide (GO) with different oxidation degrees is prepared by a modified Hummers’ method varying KMnO4 amount from 0.5 to 6.0 g. X‐ray powder diffraction (XRPD), micro–Raman, thermogravimetric analysis, X‐ray photoeelectron spectroscopy, Boehm titrations, high–resolution transmission electron microscopy, and, finally, positron annihilation lifetime spectroscopy (PALS) are exploited to assess the properties of GO. Results show that increasing oxidant species can tune the interlayer gap between GO sheets up to a maximum value in the case of 4.0 g KMnO4 content. Moreover, these results validate the two‐component‐based model of GO in which, at low oxidation degree, there are unsplit/isolated graphene planes, instead at higher oxidant amounts, a five‐layer sandwiched configuration occurs comprising graphene planes having functional groups decorating the edges (bwGO), hydrated oxidative debris (OD) and “empty” spaces (revealed by PALS as the distance between (bwGO + OD) two‐component layers). In addition, by XRPD analysis, the total gap between two sheets is easily computed. In order to correlate these findings to pollutant removal capability, planar o‐toluidine adsorption is studied. Since this molecule diffuses in an aqueous environment, the obtained adsorption percentages are compared to the thickness of the hydrated OD grafted onto bwGO. A strict connection between the pollutant removal efficacy and the variation of the hydrated interlayer distance is found.

Natural and H2SO4 modified plane sawdust as a low-cost adsorbent: Removal of anionic and cationic dyes from aqueous solutions

Natural and H2SO4-modified plane (Platanus orientalis L.) sawdust were used for the adsorptive removal of cationic methylene blue (MB) and anionic indigo carmine (IC) dyes from aqueous media to suggest a new and cost-effective method for wastewater treatment applications. The influences of initial pH values, concentrations of MB and IC, period of contact, dosages of the natural and modified plane sawdust, and the presence of foreign ions on the adsorption of dyes were investigated in the experimental studies to describe the best conditions of the most efficient adsorption processes. Initial pH values were optimized to be between 6.0-8.0 for MB and 2.0 for IC. Experimentations of Boehm titration, FTIR analysis, pHpzc value, and moisture content determinations were utilized to characterize the natural and modified sawdust materials. Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models were used to evaluate the sorption mechanism. Maximum adsorption capacities of natural plane sawdust (NPS) and H2SO4-modified plane sawdust (MPS) calculated from the Langmuir isotherm model were 55.56 and 38.46 mg g-1 in MB adsorption, and 55.82 and 55.55 mg g-1 in IC adsorption, respectively. Results showed that the natural and H2SO4-modified plane sawdust serve as low-cost and efficient materials in the adsorptive removal of MB and IC dyes for industrial wastewater treatment applications.

Removal of enalapril maleate drug from industry waters using activated biochar prepared from Butia capitata seed. Kinetics, equilibrium, thermodynamic, and DFT calculations

Porous biochar was fabricated from Butia capitata (Bc) seed, which was used to uptake enalapril maleate from synthetic wastewater. Activated biochars were fabricated by blending Bc and ZnCl2 at 1:1 (BcB-1.0) or 1:1.5 (BcB-1.5) proportions and furtherly pyrolyzed at 600 °C. The elemental analysis, Boehm titration, hydrophobic balance ratio, FTIR, TGA, and N2 isotherm characterized the carbon-based materials. They presented a hydrophilic behavior with diverse polar groups on their surface. BcB-1 and BcB-1.5 biochars have a total pore volume of 0.392 and 0.492 cm3 g−1 and a surface area of 1267 and 1520 m2/g, respectively. The kinetics and isothermal data were adequately adjusted to the fractal-like pseudo-second-order and Liu models. The employment of BcB-1.0 and BcB-1.5 for treating synthetic wastewater containing high levels of pollutants had elevated efficiency in their removals (up to 99.06%). We also conducted a DFT computational study, density functional theory (DFT), to examine the interactions between enalapril and a graphitic domain of biochar by using these calculations, the most stable configuration presented interaction energy of −88.7 kJ mol−1 implies a face-to-face π–π stacking interaction involving the enalapril phenyl segment and an aromatic ring of the graphitic domain, as well as London dispersion arising from the proximity of ethoxy/pyrrolidine to biochar carbon atoms, with interatomic distances of 3.31 Å for the former and 3.60 Å /3.48 Å for the latter. Also, the DFT calculations agreed with the thermodynamic data calculated from the isotherms (283–318 K).

Thermal treatment of H3PO4-impregnated hydrochar under controlled oxygen flows for producing materials with tunable properties and enhanced diclofenac adsorption

The chemical activation of biomass with phosphoric acid under an oxygenated atmosphere has been extensively studied in various papers. However, there is still uncertainty about how the oxygenated atmosphere affects the evolution of activated carbon properties, as the concentration of oxygen in the activation atmosphere has not been explored as an activation variable. Hence, this paper aims to fill the gap by exploring the effect of oxygen concentration on the activation process. The H3PO4-impregnated hydrochar was heated at 500 °C, under atmospheres containing various concentrations of oxygen. The evolution of activated carbons' properties was assessed by various techniques, including FTIR, SEM-EDS, N2-physisorption, CHNS/O elemental analysis, pHpzc, and Boehm titration. Additionally, the impact of oxygen concentration on the adsorption capacity was examined using diclofenac as a model pollutant. It was found that the activated carbons’ microporosity and surface functionality can be improved and controlled by changing the oxygen concentration in the activation atmosphere. This led to enhanced π-π and hydrogen bonding interactions between diclofenac molecules and activated carbons, resulting in increased adsorption capacities. This study emphasizes the importance of oxygen concentration as an activation variable, providing valuable insights for designing effective activated carbon adsorbents.

The effect of activator type on physicochemical and sorption properties of nanostructured carbon adsorbents obtained from fennel seed by chemical activation

AbstractIn this study, fennel (Foeniculum vulgare) seeds were used as a precursor for obtaining nanostructured activated carbons by chemical activation with various reagents. The obtained activated carbons were characterized using nitrogen adsorption–desorption isotherms, ash content, Boehm titration and pH of water extracts. It was shown that the choice of activator had an important effect on the physicochemical and sorption properties of the obtained activated carbons. The specific surface area of the obtained adsorbents ranged from 345 to 1052 m2/g. Chemical activation of the starting material with potassium carbonate made it possible to obtain activated carbons with the strongest developed specific surface area and the best sorption capacity against the tested pollutants. 1 g of this carbon is able to adsorb 1215 mg of iodine and 454 mg of methylene blue. The least effective adsorbent turned out to be the carbon obtained by chemical activation of fennel seeds with sodium carbonate, whose sorption capacity toward the pollutants from aqueous solutions was 77 mg/g and 317 mg/g for methylene blue for iodine, respectively. The alkaline pH of the solution promotes effective adsorption of methylene blue on the surface of the obtained adsorbents. The reaction of the dye molecules adsorption on the activated carbons occurs according to the pseudo-second-order model. The Langmuir isotherm best described the process under study. In addition, it was shown that chemical activation of fennel seeds leads to carbon adsorbents with acidic surface character. The negative values of Gibbs free energy indicate the spontaneous character of the process. The study has shown that fennel seeds can be successfully used to obtain low-cost and effective nanostructured carbon adsorbents with good sorption capacity toward organic and inorganic contaminants, from the aqueous phase.

Adsorptive Elimination of Methyl Orange Dye over the Activated Carbon Derived from Bitter Almond Shells. An Isothermal, Thermodynamic, and Kinetic Study

Abstract: Bitter almond shells (BAS) were inspected as a low-cost precursor in producing activated carbon (AC) through the optimized ZnCl2 activation route. The raw BAS were impregnated with ZnCl2 at multiple ratios (1:1 - 3:1 ZnCl2:BAS), followed by carbonization at various temperatures (400 – 800 °C) for different durations (30 – 120 minutes) in a tubular reactor. The typical AC sample was prepared using a 1:1 ZnCl2:BAS impregnation ratio and activated at 500 °C for 60 minutes. The AC yield under those conditions was 23.46%. The BET surface area (SABET), Boehm titration method, point of zero charge (pHPZC), Field Emission-Scanning Electron Microscopy (FE-SEM), X-ray diffraction (XRD), Fourier Transform Infra-Red spectroscopy (FTIR), and Energy Dispersive X-ray (EDX) of the optimal AC sample were determined. The identification outcomes disclosed that this AC sample is mesoporous with SABET, iodine number, total pore volume, and average pore width of 1221.60 m2/g, 1444.23 mg/g,1.50 cm3/g, and 4.98 nm, respectively. The adsorptive removal of methyl orange (MO) dye from its aqueous phase by this AC was accomplished at various solution pH (2–10), different amounts of the AC (0.05-0.4 g), multiple initial concentrations (50–400 mg/L), variable temperature (10-50 °C) and varied contact time (0–420 min) in a batch- mode operation. The maximum monolayer adsorption capacity of 224.71 mg/g was obtained at 323 K, pH= 2.0, initial (MO) concentration of 400 mg/L, 0.25 g AC dose, and 420 minutes contact time. The kinetic outcomes best fitted to the pseudo-2nd -order kinetics model, while the MO equilibrium capacity obeyed the Langmuir model rather than other models. Thermodynamic studies of the MO adsorption by the BAS-derived AC disclosed that the adsorption was spontaneous and endothermic. The adsorption mechanism of MO by the declared AC mostly involved electrostatic attractions and hydrogen bonding interaction. This work demonstrates that BAS is an advantageous raw material for producing low-cost and effectual mesoporous AC carbon with substantive surface area.

The valorization of rosemary waste as a new biosorbent to eliminate the rhodamine B dye

The widespread use of dyes is one of the leading causes of water contamination. Activated carbon is a common adsorbent used in water treatment by one of the most efficient physicochemical techniques: adsorption. As an agricultural waste, the conversion of unwanted rosemary biomass (stems and roots) into activated carbon material (RS-AC) was investigated using varied phosphoric acid activation ratios at 400 °C. Rhodamine B was utilized as a model dye in water in this work to understand better dye depolluting by RS-AC. Many standard methods were used to characterize the materials, including XRD, FTIR, Boehm titration, SEM/EDX, and pHzpc. The effects of RS-AC dosage, adsorption temperature, adsorption duration, and solution pH on the adsorption of Rhodamine B by RS-AC were studied better to understand the process's kinetic and thermodynamic characteristics. The thermodynamic study revealed that the adsorption process is endothermic, the pseudo-second-order kinetic model adequately explains the experimental data, and the equilibrium data showed an excellent fit to the Langmuir isothermal model for a maximum monolayer's adsorption capacity of Rhodamine B (Qmax = 65.78 mg/g). The density of function theory (DFT) was employed with the B3LYP/6-311G(d,p) base to get an idea for the activated sites on Rhodamine B and to explain the process of adsorption; eventually, the results agree with the experimental results.

Adsorption capacity of biocarbons from residue of supercritical extraction of raw plants

Abstract Bioadsorbents prepared by chemical activation (H3PO4) of the residue of supercritical extraction of green tea leaves and marigold flowers were characterized by elemental analysis, Boehm titration, adsorption/desorption isotherm and scanning electron microscopy (SEM). The adsorption performance aimed at the removal of malachite green, nitrogen oxide and hydrogen sulfide was investigated. The impacts of various influential parameters of malachite green adsorption such as: contact time (8 h), initial dye concentration (20–140 mg/L), temperature (25–65 °C) and adsorbent mass (0.015–0.025 g) were investigated. The adsorption kinetic follows pseudo second-order reaction kinetics (R 2 > 0.99). The adsorption process was best described by the Langmuir isotherm and the maximum capacity of the monolayer was from 126.58 mg/g to 333.33 mg/g for the biocarbons obtained. The negative values of Gibbs free energy indicate the spontaneous character of the process. The presence of steam in the stream of the mixture of gases had a positive effect on adsorption of nitrogen oxide and hydrogen sulfide by the bioadsorbents obtained. The most effective adsorbent of malachite green and toxic gas pollutants proved to be the biocarbon obtained from the residues of supercritical extraction of green tea leaves.

Facile production of highly active rice straw bioadsorbent to remove Cu in wastewater

A bioadsorbent with a high specific surface area and high content of oxygen-containing functional groups was prepared from silica depleted rice straw ash (SDRSA). The starting material was a by-product of rice straw after alkoxysilane extraction. The maximum adsorption capacity of SDRSA for copper ions was 26.7 mg/g, which was higher than previously reported biomass adsorbents. The effects of adsorbent dose, pH, contact time, and other conditions on the adsorption performance of SDRSA on Cu2+ were investigated. The adsorption process of Cu2+ on SDRSA was well fitted by the Langmuir isotherm model and the pseudo-second-order kinetic model. The physicochemical properties and adsorption mechanism of SDRSA were investigated by specific surface area testing (BET), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Boehm titration methods. Electrostatic interaction, complexation, ion exchange, and precipitation are the possible Cu2+ removal mechanisms. The preparation method requires only simple washing and drying, and the alcohol can be distilled and recycled. Thus, SDRSA is very low cost and convenient to prepare in large quantities. This work presents a novel approach to optimize adsorbent production to mitigate heavy metal pollution.

Characterisation of the surface chemistry of carbon materials by temperature-programmed desorption: An assessment

The increasing role assumed by carbon materials in technological applications is intrinsically linked to a better understanding of carbon surface chemistry as a result of reliable methods of analysis. X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD) techniques allow to obtain qualitative and quantitative information on individual functional groups on the carbon surface. In this context, TPD has established itself as an alternative technique to the Boehm titration methodology or XPS, being especially adequate for the characterisation of oxygen functional groups on carbon materials with extended porosity. This work reviews the fundamentals and methodology to perform a correct TPD-MS analysis and assessment (qualitatively and quantitatively) of the oxygenated functional groups. The applicability of the information obtained by TPD to correlate the properties of carbon materials with their performance in practical applications is also revised.

Dacryodes edulis leaf derived biochar for methylene blue biosorption

Carbonized Dacryodes edulis leaf (CDEL) which was obtained at 250 °C, was used for the biosorption of methylene blue (MB) dye from aqueous solutions. The biosorbent was characterised using Boehm titration, pH of zero point charge (pHzpc), FTIR, SEM, XRD and ED-XRF. Mineral compositions of CDEL revealed good amounts of Fe, Ca and K which are of nutritional importance. The pH at zero point of charge (pHzpc) and specific surface area (SSA) of CDEL were found to be 7.5 and 0.983 m2/g respectively. Freundlich isotherm gave good fit to equilibrium biosorption data. Elovich kinetic model gave the best fit to kinetic data which is consistent with chemisorption. Scanning electron microscopy (SEM) and infrared spectroscopy (FTIR) revealed effective biosorption processes. Calculated thermodynamic parameters revealed spontaneous and exothermic biosorption of MB onto CDEL. Highest amount of MB was removed at pH 4 and the percentage removal was about 93%; hence, CDEL is a good biosorbent for MB from aqueous solutions. Generally, CDEL exhibited > 70% MB removal after three adsorption-desorption cycles, showing that it is re-usable and a promising biosorbent for the treatment of MB dye contaminated water.

Development of mesoporous activated carbon from waste tires rubber via one-step activation using a blend of ZnCl2/FeCl3 and its application in Eriochrome Black T and Cr(VI) removal from aqueous phase

ABSTRACT A mesoporous activated carbon (MAC) was synthesized from waste tires rubber (WTR) via a one-step ZnCl2/FeCl3 activation route, and the typical sample was implemented in eliminating Eriochrome Black-T (EBT) dye and Cr(VI) from their synthetic effluents. The impact of the impregnation ratio of ZnCl2/FeCl3, the activation temperature, and the activation period was optimized . The best AC was created at 750°C for 60 minutes using a 2:1 ZnCl2/FeCl3:WTR impregnation ratio. This AC was analyzed for its BET surface area and pore volume, Fourier Transform Infra-Red spectroscopy (FTIR), X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX), Boehm titration, and pHPZC. The outcomes disclosed that it had a surface area of 122.68 m2/g with a mean pore diameter of 8.53, indicating its mesoporosity. It also exhibited an acidic surface due to its pHPZC, which amounted to 4.80. The highest elimination of EBT (99.33%) and Cr ions (98.05%) from thier aqueous phases was achieved using 0.35 g dosage of MAC, a pH = 2.0 at 40°C for 210 minutes. The EBT and Cr(VI) isothermal and kinetics studies disclosed that the Langmuir and pseudo-2nd-order models best described their adsorption over the said AC. Thermodynamic functions showed that the MAC adsorption for EBT and Cr(VI) was endothermic and spontaneous. Reusability tests suggested that the regenerated AC could be utilized four times with reasonable efficiency. In conclusion, the application of the MAC described above because of its high efficiency in eliminating EBT and Cr(VI) from synthetic samples can be assessed in future studies to be applied in actual scales.

Adsorption of a Four-Component Mixture of Volatile Organic Compound Vapors on Modified Activated Carbons

This work aimed to evaluate the effect of activated carbon modifications on the adsorption of volatile organic compound vapors. In this study, two commercial activated carbons WG-12 and DT0 (Grand Activated Sp. z o.o.) were modified by melamine and dl-malic acid and heat treatment. Then, the activated carbons were used as adsorbents in the adsorption of a gaseous mixture of four volatile organic compounds (acetone, ethyl acetate, toluene, n-butyl acetate) from the air. The properties of modified adsorbents were described using thermogravimetric analysis, elemental analysis, Boehm titration, and iodine number. Adsorption processes were characterized by breakthrough curves, velocities of the sorption front migration, and the Yoon–Nelson model. The study showed that surface modifications of activated carbons affect the adsorption properties of a mixture of acetone, ethyl acetate, toluene, and n-butyl acetate. The introduction of nitrogen on the surface of the activated carbons did not significantly improve the adsorption efficiency. It was identified that increasing the degree of carbonization of the activated carbon favored the adsorption of the tested adsorbates. The adsorption process of this mixture occurs by diffusion and depends on the diffusion velocity of the adsorbate molecules in the pores. It has been demonstrated that the velocity of the sorption front migration is inversely proportional to the boiling point of the adsorbates. In addition, it was found that competitive adsorption takes place in this process. Modified adsorbents can be thermally regenerated with almost 100% efficiency and reused in the next adsorption process. Furthermore, the Yoon–Nelson model can be successfully used to describe the kinetics of this process up to the point of displacement.

Adsorption of cationic dye on nanostructured biocarbons: kinetic and thermodynamic study

AbstractNanostructured bio-adsorbents were prepared by physical or chemical activation of the residue of supercritical extraction of raspberry seed. Their physicochemical properties were determined by elemental analysis, low-temperature nitrogen adsorption/desorption, Boehm titration and scanning electron microscopy. The biocarbon obtained as a result of physical activation of the precursor showed basic character of the surface and its SBET was 700 m2/g. The chemical activation of the residue of supercritical extraction of raspberry seed with potassium carbonate favored generation of acidic functional groups and SBET of this biocarbon was 1177 m2/g. The nanostructured biocarbons were used for removal of Rhodamine B from its aqueous solutions. The process was best described by the Langmuir isotherm and the maximum capacity of the monolayer was 181.82 mg/g and 277.83 mg/g for the physically and chemically activated samples, respectively. The adsorption energy obtained from the Dubinin–Radushkevich isotherm indicated that the process observed was physisorption, while the kinetics of the process was best described by the pseudo-second-order model. The negative values of Gibbs free energy indicated the spontaneous character of the process. For the chemically activated sample, the highest sorption capacities toward Rhodamine B were obtained in an acidic environment, while for the physically activated sample—in a basic environment. The yield of desorption decreased for the media: distilled water > hydrochloric acid > acetic acid, which means that Rhodamine B molecules were weakly bound to the biocarbon surface.

Production of Activated Carbons from Food/Storage Waste

This paper deals with the adsorption of organic and inorganic pollutants on the surface of carbonaceous adsorbents prepared via the chemical activation of expired or broken food products-the solid residue of the "cola-type" drink as well as spoilt grains of white rice and buckwheat groats. The activation process was conducted in the microwave furnace with the use of two activating agents of different chemical nature-potassium carbonate and orthophosphoric acid. The activated carbons were characterized based on the results of elemental analysis, low-temperature nitrogen adsorption/desorption, Boehm titration, thermal analysis, and scanning electron microscopy. Additionally, the suitability of the materials prepared as the adsorbents of methylene blue and iodine from the aqueous solutions was estimated. The materials obtained via chemical activation with H3PO4 turned out to be much more effective in terms of both model pollutant adsorptions. The maximum sorption capacity toward iodine (1180 mg/g) was found for the white-rice-based activated carbon, whereas the most effective in the methylene blue removal (221.3 mg/g) was the sample obtained from the solid residue of the expired "cola-type" drink. For all carbonaceous materials, a better fit for the experimental adsorption data was obtained with the Langmuir isotherm model than the Freundlich one.

Effective biosorption of As(V) from polluted water using Fe(III)-modified Pomelo (Citrus maxima) peel: A batch, column, and thermodynamic study

Pomelo, Citrus maxima, peel was chemically modified with lime water and then loaded with Fe(III) to develop anion exchange sites for effective sequestration of As(V) from water. Biosorbent characterizations were done by using FTIR, SEM, XRD, EDX, and Boehm's titration. The batch biosorption studies were carried out at various pHs using modified and non-modified biosorbents and optimum biosorption of As(V) occurred at acidic pH (3.0–5.0) for both the biosorbents. A kinetic study showed a fast biosorption rate and obtained results fitted well with the pseudo-second-order (PSO) model. When isotherm data were modeled using the Langmuir and Freundlich isotherm models, the Langmuir isotherm model fit the data better and produced maximal As(V) biosorption capacities of 0.72 ± 03, 0.86 ± 06, and 0.95 ± 05 mmol/g at temperatures 293± 1K, 298± 1K and 303± 1K, respectively. Desorptionof As(V) was effective using 0.1 M NaOH in batch mode. Negative values of ΔG° for all temperatures with positive ΔH° confirmed the spontaneous and endothermic nature of As(V) biosorption. The existence of co-existing chloride (Cl−), nitrate (NO3−), sodium (Na+), and calcium (Ca2+) showed insignificant interference whereas a high concentration of sulphate (SO42−) and phosphate (PO43−) significantly lowered As(V) biosorption percentage. Arsenic concentrations in actual arsenic polluted groundwater could be reduced to the WHO drinking water standard (10 μg/L) by using only 1 g/L of investigated Fe(III)-SPP. The dynamic biosorption of As(V) in a fixed bed system showed that Fe(III)-SPP was effective also in continuous mode and different design parameters for fixed bed system were determined using Thomas, Adams-Bohart, BDST, and Yoon-Nelson models. Therefore, from all of these results it is suggested that Fe(III)-SPP investigated in this study can be a potential, low cost and environmentally benign biosorbent material for an effective removal of trace amounts of arsenic from polluted water.