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Activated carbons obtained via the thermochemical treatment of lemon balm and mint herbs were applied for ionic polymers adsorption, which directly affects the stability of these types of aqueous suspensions. The examined carbonaceous materials were characterized by well-developed specific surface area (approximately 1000 m2/g) and mesoporous structure. The adsorbed amounts of anionic poly(acrylic acid) and cationic polyethyleneimine from one-component solutions reached significant levels, but the efficiency of adsorption of these compounds from binary solutions slightly decreased. Moreover, the ionic polymers showed stabilizing properties towards the activated carbons suspensions. For both adsorbents, the most stable suspensions were systems containing both types of polymeric macromolecules with different ionic characters. This was due to the occurrence of electrosteric and depletion stabilization mechanisms. Furthermore, the zeta potential and size of particle aggregates were also influenced by the presence of polymers in the aqueous suspensions of activated carbons. [ABSTRACT FROM AUTHOR]

The main objective of this study was to assess the usefulness of the low-quality brown coal, ash obtained as a result of its combustion, as well as used gear oil for the production of mineral-carbon adsorbents. The adsorbents were characterized in terms of textural parameters, acidic-basic character of the surface, mineral matter contribution to the structure, as well as their suitability for drinking water purification. Adsorption tests were carried out against two synthetic dyes—methylene blue and methyl orange. In order to understand the nature of the organic pollutants adsorption, the effect of the initial dye concentration, temperature, and pH of the system as well as the phase contact time were investigated. The obtained mineral-carbon composite and activated carbons significantly differed not only in terms of the elemental composition and chemical character of the surface (from slightly acidic to strongly alkaline), but also showed a very diverse degree of specific surface development (from 21 to 656 m2/g) and the type of porous structure generated (from micro/mesoporous to typically mesoporous). Adsorption tests showed that the efficiency of organic dye removal from aqueous solutions primarily depends on the type of the adsorbent and adsorbate applied, and, to a lesser extent, on the temperature and pH of the system. In turn, kinetic studies have shown that the sorption of dyes on such materials is consistent with a pseudo-second-order kinetics model, regardless of the type of adsorbed dye. [ABSTRACT FROM AUTHOR]

The thermal behaviour of hay-based activated carbons modified with adsorption nanolayers of ionic polymers were investigated. The anionic and cationic forms of polyacrylamides (PAM) with different contents of ionizable groups were applied. Using spectrophotometry, potentiometric titration, microelectrophoresis, DCS (Differential Centrifugal Sedimentation) and thermal analysis methods, the adsorption and electrokinetic, properties, as well as thermal stability of studied activated biocarbons—PAM systems were established. It was shown that PAM adsorbed amounts on the activated biocarbon surfaces were considerably higher for cationic polyacrylamides than for anionic ones. The conducted TG-DSC-FTIR/MS analysis in helium showed a significant influence of the synthesis conditions on the content of oxygen surface groups of activated biocarbons obtained in conventional or microwave muffle furnace. The measurements carried out in the oxidizing atmosphere for the polymer-modified samples showed similarity to the original materials and were characterized by three main stages of decomposition: dehydration, decomposition of surface functional groups and, at high temperatures—combustion process. The main decomposition products were CO2 and H2O. [ABSTRACT FROM AUTHOR]

Biochars and activated carbons obtained from the nettle and the sage herbs were used for Cd(II), As(V), poly(acrylic acid) and polyethylenimine simultaneous adsorption from the multicomponent aqueous solutions. Electrokinetic studies proved that both activated carbons show acidic character of the surface. The point of zero charge of the sample obtained from the nettle herb occurs at pH 3.1, whereas that of the adsorbent obtained from the sage herb at pH 4.0. Cd(II) adsorption causes the decrease in the surface charge density and the zeta potential of both activated carbons, whereas As(V) addition results in the increase of solid surface charge density and its impact on the zeta potential value depends on adsorbent type. In case of the simultaneous presence of metals and polymers, the adsorbed macromolecules have greater influence on the surface charge density and the zeta potential values than the metal ions. Cd(II) and As(V) are well adsorbed on the examined activated carbons irrespective of the solution pH (changing in the range 3–9). Maximum adsorption were 218.27 mg/g for Cd(II) and 205.53 mg/g for As(V). The polymers presence causes a decrease (80–90 %) of both metal ions adsorbed amounts, whereas the poly(acrylic acid) and polyethylenimine adsorption mechanism in the presence of cadmium and arsenic ions depends on the adsorbent type and polymer-metal interactions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The main aim of this study was the determination of temperature influence on adsorption mechanisms of anionic poly(acrylic acid) (PAA) and cationic polyethylenimine (PEI) on the surface of activated carbons (AC) obtained via chemical activation of nettle (NE) and sage (SA) herbs. All measurements were performed at pH 3 at three temperature values, i.e., 15, 25 and 35 °C. The adsorption/desorption of these polymers from single and mixed solution of adsorbates was also investigated. The viscosity studies were additionally performed to obtain hydrodynamic radius values characterizing polymeric macromolecules conformation in the solution. These data are very important for the explanation of changes of linear dimensions of polymer chains with the rise of temperature caused by the modification of polymer–solvent interactions. Moreover, the XPS studies for the systems showing the highest adsorbed amounts in the specific temperature conditions were carried out. These were the systems containing PEI, PAA and NE–AC activated carbon at 25 °C. In such a case, the maximum adsorption capacity towards PAA macromolecules from a single solution of adsorbate reaches the value of 198.12 mg/g. Additionally, the thermodynamic parameters including the free energies of adsorption, as well as changes in free enthalpy and entropy were calculated. [ABSTRACT FROM AUTHOR]

Nettle and the sage herbs were used to obtain carbonaceous adsorbents. For the biochar preparation the precursors were dried and subjected to conventional pyrolysis. Activated carbons were obtained during precursor impregnation with phosphoric(V) acid and multistep pyrolysis. The textural parameters and acidic-basic properties of the obtained adsorbents were studied. The activated carbons prepared from the above herbs were characterized by the largely developed specific surface area. The obtained carbonaceous adsorbents were used for polymer removal from aqueous solution. Poly(acrylic acid) (PAA) and polyethylenimine (PEI) were chosen, due to their frequent presence in wastewater resulting from their extensive usage in many industrial fields. The influence of polymers on the electrokinetic properties of activated carbon were considered. PAA adsorption caused a decrease in the zeta potential and the surface charge density, whereas PEI increased these values. The activated carbons and biochars were used as polymer adsorbents from their single and binary solutions. Both polymers showed the greatest adsorption at pH 3. Poly (acrylic acid) had no significant effect on the polyethylenimine adsorbed amount, whereas PEI presence decreased the amount of PAA adsorption. Both polymers could be successfully desorbed from the activated carbons and biochar surfaces. The presented studies are innovatory and greatly required for the development of new environment protection procedures. [ABSTRACT FROM AUTHOR]

The thermal analysis methods were used for the description of the adsorption behaviour of selected proteins differing in internal stability (ovalbumin (OVA) and lysozyme (LSZ)). These proteins were immobilised on the surface of activated biocarbon obtained from the horsetail herb precursor. The values of the hydrodynamic radius of both biopolymer macromolecules in the solution were determined by the use of the viscosimetry method. This parameter is important for the specification of the possibility of proteins nano-molecules to penetrate the nano-pores of the adsorbent which leads to the increase of biopolymers adsorption. Such behaviour is observed at the pH value which is very close to the pI value of specific biopolymer (the greatest adsorption of proteins on the activated carbon surface occurs- at pH 5 for OVA being 323 mg/g, as well as at pH 11 for LSZ which is 464 mg/g). Under such conditions, the proteins macromolecules assume conformations characterized by the lowest values of hydrodynamic radius, i.e. 2.76 nm for OVA and 1.07 nm for LSZ. The data obtained from the analysis of gaseous products of thermal decomposition of the samples indicated the types of biocarbon surface groups as well as the enabled specification of the protein macromolecules adsorption mechanism. [ABSTRACT FROM AUTHOR]

• Thermal degradation of activated carbons obtained from peat was examined. • Effect of solid surface modification by polymer (PAA) and surfactant (SDS) was studied. • TG, DTG and DSC coupled with FTIR and QMS spectrometry were applied. • Polymer/surfactant mixed layers influences thermal behaviour of carbon materials. The thermal behaviour of activated carbons obtained from peat and modified with poly(acrylic acid) - PAA films was examined. Additionally, the effect of anionic surfactant – sodium dodecyl sulfate (SDS) presence in the adsorption layer was determined. Three samples of activated carbons were analyzed: (1) sample N - obtained by pyrolysis of peat followed by steam activation, (2) sample N9C - obtained by physical activation of sample N with carbon dioxide and (3) sample N9K - obtained by chemical activation of sample N with potassium carbonate. TG, DTG and DSC coupled with FTIR and QMS spectrometry enable not only specification of thermal stability of examined systems, but also determination of main gaseous products of their thermal decomposition. The obtained results indicate that polymer/surfactant adsorption influences significantly the thermal degradation of used carbon materials. [ABSTRACT FROM AUTHOR]

• Modified method of lignocellulose content determination was elaborated. • Difficult lignin quantification with calibration curve usage was eliminated. • New cellulose determination method was proposed. • The developed procedure was checked on selected herbs. Determination of extractives, lignin, hemicellulose, cellulose and mineral substance is a complex procedure. Lignin and hemicellulose are both alkali soluble and their mutual determination is disturbed. Moreover, the lignin occurs in two fractions - soluble and insoluble in acids, which make its determination difficult. In this paper a new, modified method of all the above components determination was described. The inaccuracies in methods reported in the literature so far were solved. There was applied not sophisticated equipment aimed at the costs reduction. The complicated, multistep lignin content determination was replaced by easier procedure of cellulose evaluation. Moreover the hemicellulose determination was improved (the error related with lignin dissolution in alkaline solution was eliminated). The presented method was used for the nettle, sage, lemon balm and mint herbs analyses. The herbs contain a small percentage of mineral substance and are very suitable for the activated carbons preparation. It has been shown that the content of hemicellulose affects the activated carbons surface area development, whereas the lignin content has influence on the concentration of total surface functional groups. Activated carbons with the best surface properties were obtained from the herbs containing high concentrations of hemicellulose and lignin. [ABSTRACT FROM AUTHOR]

Biochars are obtained by biomass pyrolysis, whereas activated carbon is a biochar that has undergone chemical or physical activation. Owing to the large surface area and easy surface modification both solids are widely applied as adsorbents. They are low-costs materials, they could be regenerated and their disposal is not troublesome. Adsorption of heavy metals, dyes, pharmaceuticals on the surface of biochars and activated carbons, from simple systems of adsorbate containing only one compound, are described extensively in the literature. The present paper provides an overview of reports on adsorption of inorganic and organic compounds onto these two types of adsorbents from the mixed adsorbate systems. The described adsorbate systems have been divided into those consisting of: two or more inorganic ions, two or more organic compounds and both of them (inorganic and organic ones). The research of this type is carried out much less frequently due to the more complicated description of interactions in the mixed adsorbate systems. [Display omitted] • Simultaneous adsorption of inorganic and organic compounds are reported. • Biochars and activated biocarbons as hazardous substances adsorbents were applied. • Heavy metal removal from their mixed solution was described. • Adsorption of dyes from the multi-component solutions was investigated. • The mutual synergistic and antagonistic actions depend on adsorbate and solid surface properties. [ABSTRACT FROM AUTHOR]

Two samples of activated biocarbons obtained from corncobs and peanut shells precursors were applied for poly(acrylic acid) – PAA macromolecules adsorption from the aqueous solutions containing surfactants with different ionic character (non-ionic Triton X-100, cationic CTAB and anionic SDS). The effects of biocarbon structure, solution pH and surfactant type were examined. The structure of PAA adsorption layer without and with surfactant molecules on the activated carbons surface was described based on the adsorption, electrokinetic and stability results obtained from the spectrophotometric experiments, potentiometric titrations, electrophoretic mobility measurements and stability tests. It was shown that the presence of surfactant influences significantly the adsorption affinity of PAA macromolecules for the micro/mesoporous biocarbons and causes changes in both solid suspensions stability. [Display omitted] • Activated biocarbons from corncobs and peanut shells precursors were applied. • PAA adsorption from solutions containing different surfactants was examined. • Effects of biocarbon structure, solution pH and surfactant type were studied. • Surfactant influences significantly mechanisms of PAA adsorption and stability. • Polymer-surfactant complexes and competition between both adsorbates occur in examined systems. [ABSTRACT FROM AUTHOR]

The activated carbons obtained from peat were applied for simultaneous removal of low-molecular weight poly(acrylic acid) – PAA (2 000 Da) and sodium dodecyl sulfate (SDS) from their mixed solution. There were applied three samples of activated carbons: N – obtained by peat pyrolysis followed by the steam activation, N9C – obtained from N by means of physical activation with CO 2 and N9K – obtained from N by chemical activation with K 2 CO 3. The final products are characterized by mesoporous structure, well-developed surface area and specific acidic-basic properties of the surface. The effect of solution pH, influencing PAA chains conformation (changes in polymer carboxyl groups dissociation) and solid surface charge density were examined. The applied adsorbents were characterized using the low-temperature nitrogen adsorption-desorption method, Fourier-transform infrared spectroscopy (FTIR), elemental analysis and back-titration method. Moreover, the adsorption affinity of PAA and SDS for the activated carbon surface was characterized based on the adsorption and electrokinetic data obtained from the spectrophotometric experiments, potentiometric titrations and zeta potential measurements. Additionally, the sizes of poly(acrylic acid) chains (hydrodynamic radius) in the solution as a function of pH were determined based on viscosity measurements. It was demonstrated that under specific pH conditions the prepared activated carbons exhibit high adsorptive affinity for PAA chains (reaching about 265 mg/g). Furthermore, it was also proved that these adsorbents can be successfully regenerated (using an appropriate desorbing agent) and reused. Therefore the low-cost activated carbons can be used for simultaneous removal of undesirable low-molecular polymers and surfactants from wastewaters. [ABSTRACT FROM AUTHOR]

The activated biocarbons obtained from corncobs and peanut shells were applied for simultaneous removal of poly(acrylic acid) – PAA macromolecules and lead(II) ions from their mixed solution. The biocarbons were prepared via the two-step chemical activation, including pyrolysis of the precursors at 500 °C in nitrogen atmosphere, followed by impregnation with K 2 CO 3 and heat treatment at 800 °C. The obtained materials were characterized using the low-temperature nitrogen adsorption-desorption method, elemental analysis and back-titration method. The activation products were micro/mesoporous biocarbons of medium developed surface area (862 and 654 m2/g, respectively), showing slightly acidic character of the surface. The average molecular weight of PAA ensured penetration of polymer coils into the adsorbent pores under specific pH conditions. The nanostructure of PAA adsorption layer without and with Pb(II) cations on the activated carbons surface was characterized based on the adsorption, electrokinetic, stability and microscopic data obtained from the spectrophotometric experiments, both potentiometric titration and zeta potential measurements, turbidimetric experiments and SEM imaging, respectively. It was shown that the micro/mesoporous biocarbons are effective and cheap adsorbents for simultaneous removal of polymeric macromolecules and heavy metal ions from the liquid medium (the presence of both adsorbates has an extremely favorable effect on their adsorbed amounts). Image 1 • Corncobs- (CPA) or peanut shells- (NPA) based activated biocarbons were prepared. • Adsorption mechanism of anionic PAA polymer and Pb(II) cations was examined. • Mesoporous biocarbons removes polymer-metal complexes effectively at pH 3. • The solid-polymer-metal aggregates can be effectively separated from liquid phase. • Maximal PAA and Pb(II) adsorption reaches about 200 and 400 mg/g, respectively. [ABSTRACT FROM AUTHOR]