The removal of hazardous ions from water is crucial for safeguarding both the environment and human health. Soil minerals, integral components of soil, play a vital role as adsorbents for various ...contaminants, including heavy metal ions, organic dyes, and detergents. This study investigates the interaction between boron ions and soil minerals (gibbsite, kaolinite, and montmorillonite) in the presence of polyethylenimine (PEI). The minerals underwent characterization based on specific surface area, particle size distribution, zeta potential, and the presence of functional groups. The influence of PEI addition on the stability of the soil mineral suspension was evaluated by turbidimetry. Mineral−boron and mineral−boron−PEI interactions were explored under varying conditions, including pH, initial boron concentration, and mineral quantity, with all adsorption experiments conducted over 24 hours. Using the Langmuir isotherm, the maximum adsorption capacity of the studied minerals was determined for boron both without and in the presence of PEI. For gibbsite, kaolinite and montmorillonite, it was 30.63, 24.55 and 26.62 mg g−1, respectively, while in the presence of PEI, it increased to 33.11, 26.61 and 45.47 mg g−1, respectively. The addition of PEI enhanced boron adsorption from aqueous solutions, increasing the removal efficiency from 65 % to about 80 %.
The adsorption of boron in the presence of PEI affects the minerals′ electrical double layer (EDL) structure, manifested in the altered electrokinetic properties of the material. The addition of PEI increases the adsorption capacity of the tested soil minerals towards boron, as the additional amino groups of PEI provide additional active sites for boron adsorption.
Diclofenac is one of the most popular over‐the‐counter non‐steroidal anti‐inflammatory drug and poly(acrylic acid) is a frequently used as thickener, filler or stabilizer. For these reasons, they are ...common organic contaminants in raw wastewater. The purpose of the presented studies was to compare the adsorption capacity of three carbon‐silica composites – metal‐free C/SiO2, iron‐enriched C/Fe/SiO2 and manganese‐enriched C/Mn/SiO2 towards diclofenac. The studies were carried out in single, and mixed systems in the presence of poly(acrylic acid) polymer. Adsorption, desorption and kinetics of the adsorption process were investigated. The concentration of diclofenac in the supernatants was determined using high‐performance liquid chromatography. The solids were also characterized with an ASAP apparatus using low‐temperature nitrogen desorption adsorption isotherms at liquid nitrogen temperature. In addition, potentiometric titrations and electrophoretic mobility measurements, as well as stability tests of the studied suspensions were carried out. The most efficient composite among investigated ones proved to be C/Fe/SiO2 removing diclofenac at the level of 46.68 mg/g for its initial concentration of 90 ppm. The results obtained clearly demonstrated that the carbon‐silica composites are effective in separation of drugs from aqueous solutions and can be successfully used in the future for the removal of organic pollutants from water environment.
New carbon‐silica adsorbents enriched with Fe and Mn metals were synthesized. They were characterized in terms of porous structure, surface properties, as well as electrokinetic and stability behavior. These carbon‐based materials were used for the adsorptive removal of diclofenac – the over‐the‐counter nonsteroidal anti‐inflammatory drug, also in the presence of poly(acrylic acid).
Two series of hydrogels based on acrylamide and its copolymers with acrylonitrile and acrylic acid were synthesized by two cross‐linking methods – chemical (using N,N′‐methylene bis‐acrylamide) and ...physical (using montmorillonite (MMT)) ones. The structure of the gels was characterized by Fourier Transform Infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The swelling and sorption properties were analyzed as a function of both the monomer composition and the cross‐linking method. The shift of the band corresponding to Si−O (995–1030 cm−1) confirmed the formation of intercalation structures for MMT‐cross‐linked gels. Moreover, physically cross‐linked gels demonstrated a non‐monotonic dependence of the swelling degree on the MMT concentration, and acrylamide‐acrylic acid copolymer MMT‐cross‐linked gels showed pH sensitivity and the highest swelling degree of 150 g/g. The highest sorption capacity towards cadmium(II) ions was demonstrated by acrylamide‐acrylic acid copolymer gels, both covalently cross‐linked (30 mg/g) and MMT‐cross‐linked (8.9 mg/g).
Montmorillonite cross‐linked hydrogels based on acrylamide and its copolymers with acrylonitrile and acrylic acid were synthesized and compared to N,N′‐methylene‐bis‐acrylamide cross‐linked ones. Clay‐cross‐linked hydrogel with acrylonitrile showed higher sorption capacity towards Cd(II) than chemically cross‐linked one.
This study presents an assessment of inorganic and organic modification of biochar on physicochemical properties, dissolved organic carbon (DOC) release, sorption efficiency towards enrofloxacin (E) ...and silver nanoparticles (Ag–NPs), as well as an evaluation of addition of prepared materials on hydro–physical properties and adsorption capacity of montmorillonite (M). The biochar was derived from wheat straw at 650 °C. An inorganic modification was performed using ammonia hydroxide, whereas an organic modification, using citric acid. The ammonia hydroxide and citric acid changed the biochar nature and surface chemistry by introducing amino and ester groups. The lowest DOC release was from ammonia–biochar (BCN) and the highest, from citric acid–biochar (BCC). The adsorption data were better described by pseudo–II order equation and Marczewski–Jaroniec isotherm. Results showed that BCN exhibited the highest efficiency in adsorption of E and Ag–NPs. It also improved the adsorptive abilities and saturated hydraulic conductivity of M. This provides the chemically modified biochars have an excellent potential to improve pollution removal from aqueous media and hydro–physical/sorption properties of soil sorption complex. They can be used with advantageous in environmental applications.
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•Chemical modified biochars were prepared using ammonia hydroxide and citric acid.•The lowest release of dissolved organic carbon was from ammonia–biochar.•Biochar modification enhanced antibiotic and nanoparticle removal in aqueous media.•Ammonia–biochar addition improved hydro–physical properties of montmorillonite.•The modified biochars exhibited excellent potential for environmental applications.
A series of carbon composites were synthesised by carbonisation of resorcinol‐formaldehyde resin mixtures with the addition of different amounts of sodium alginate (SA) and compared with a composite ...prepared using Na2CO3 as a catalyst for the polymerisation reaction. The effect of operating parameters such as SA concentration and polycondensation time on the structural and morphological properties of resorcinol‐formaldehyde resins (RFR) and carbon‐derived composites was investigated for further use as adsorbents. The synthesised composites were characterised by FTIR, SEM, Raman spectroscopy and N2 adsorption/desorption techniques. It was found that the morphology, specific surface area (SBET~347‐559 m2/g), volume and particle size distribution (~0.5–4 μm) and porosity (Vpor=0.178–0.348 cm3/g) of the composites were influenced by the concentration of SA and the synthesis technique and determined the adsorption properties of the materials. It was found that the surface of the filled chars was found to have an affinity for heavy metals and has the ability to form chemical bonds with cadmium ions. The maximum sorption capacities for Cd(II), i. e. 13.28 mg/g, were observed for the sample synthesised with the highest SA content. This confirms the statement that as‐synthesised materials are promising adsorbents for environmental applications.
A series of porous carbons were synthesized by pyrolysis of a mixture of resorcinol‐formaldehyde resin and sodium alginate. The influence of biopolymer content and time of polycondensation on the structural and adsorption properties of the precursors and their carbons was investigated. The nanocomposites can be effectively used to remove Cd(II) from aqueous solution with a maximum removal efficiency of 13.28 mg/g.
Chemical modification of biochars can improve their adsorption capacity relative to antibiotics, posing a serious threat to the environment. Therefore, this research is aimed at the treatment of ...sunflower husk biochar (BC) by vitamin C, hydrogen peroxide or silver nanoparticles and the impact of this procedure on the biochar porosity, surface chemistry, and ability to remove tetracycline (TC). During the study, BC was produced by pyrolysis of sunflower husks at 650 °C. All solids were characterized using potentiometric titration, nitrogen adsorption/desorption, Fourier transform infrared spectroscopy, etc. The experimental adsorption data was described by kinetics equations: pseudo-first order, pseudo-second order, and particle internal diffusion (IPD) models as well as by isotherms of Langmuir, Langmuir-Freundlich, and Redlich-Peterson. The obtained results indicated that the biochar upgraded by vitamin C (BCV) had the highest ability to attract antibiotic molecules and, as a result, the TC adsorption on its surface was the largest. Furthermore, the TC desorption from this material was minimal. The measured TC adsorbed amounts for the modified BCs were as follows: 47.75% (7.47 mg/g) for BCV, 37.35% (8.41 mg/g)-for biochar treated by hydrogen peroxide (BCH), and 42.04% (9.55 mg/g) for biochar modified by silver nanoparticles (BCA). The lowest adsorption level was noted for non-modified biochar, i.e., 34.17% (6.83 mg/g). Based on the presented results it can be stated that the upgraded biochars had a good potential to improve the tetracycline removal from aqueous media, e.g., groundwater.
Purpose
Heavy metal soluble forms pose a threat to plants, soil microflora, and microfauna. To limit their toxicity and mobility, various immobilizing additives are being developed. The main aim of ...the study was to determine the influence of soil flocculant (cationic polyacrylamide (CtPAM)) on the hexavalent chromium ion reduction and accumulation on the kaolinite surface. In this way, the efficiency of the selected polymer conditioner in the soil remediation was determined.
Materials and methods
The adsorbed amounts of Cr(VI) and CtPAM on the kaolinite surface was determined spectrophotometrically (spectrophotometer UV/Vis) using specific indicators. The structure of electrical double layer formed on the kaolinite surface in the mixed system of cationic polyacrylamide and Cr(VI) ions was described based on the adsorptive measurements, zeta potential measurements, as well as potentiometric titration. The kaolinite aggregation in the presence of CtPAM and/or Cr(VI) ions was determined spectrophotometrically and proved using SEM microscopy. The reduction process of Cr(VI) to Cr(III) occurring in the adsorption layer was determined by diffuse reflectance spectroscopy (DRS).
Results and discussion
The obtained results indicated that cationic polyacrylamide contributes to Cr(VI) reduction to Cr(III) form in the kaolinite suspension. This heavy metal ions are strongly adsorbed by the applied clay mineral, especially at pH 5 (then the Cr(VI)-adsorbed amount equals 5.42 mg/g). The CtPAM addition favors the Cr(VI) ion immobilization on the kaolinite surface. In the conditioner presence, the heavy metal-adsorbed amount is even at 7.34 mg/g. The adsorption of CtPAM and chromium(VI) ions induces changes in the kaolinite surface charge density and electrokinetic potential. What is more, both substances favors the kaolinite aggregation.
Conclusions
Cationic polyacrylamide may be considered a substance reducing the toxicity of chromium(VI) ions in the natural environment and decreasing their availability for soil organisms. It can improve the soil structure (by stimulating aggregation) and reduce environment pollution with heavy metals simultaneously.
Graphical abstract
Pure zeolite (Na-X) and a zeolite–carbon composite (Na-X(C)) were investigated as adsorbents of heavy metals—Pb2+ and Zn2+ from an aqueous solution. These materials were synthesized from fly ash—a ...waste from conventional hard coal combustion. Both solids were characterized using XRD, SEM-EDS, nitrogen adsorption/desorption, particle size and elemental composition analyses. The adsorption study was performed at pH 5 in the systems containing one or two adsorbates simultaneously. The obtained results showed that the pure zeolite was characterized by a more developed surface area (728 m2/g) than its carbon composite (272 m2/g), and the mean pore diameters were equal to 1.73 and 2.56 nm, respectively. The pure Na-X zeolite showed better adsorption properties towards heavy metals than its Na-X(C) composite, and Zn2+ adsorbed amounts were significantly higher than the Pb2+ ones (the highest experimental adsorption levels were: for Zn2+—656 and 600 mg/g, and for Pb2+—575 and 314 mg/g, on the Na-X and Na-X(C) surfaces, respectively). The zinc ions are exchanged with the cations inside the zeolite materials structure more effectively than lead ions with a considerably larger size. In the mixed systems, the competition between both heavy metals for access to the active sites on the adsorbent surface leads to the noticeable reduction in their adsorbed amounts. Moreover, the hydrochloric acid was a better desorbing agent for both heavy metals, especially Pb2+ one (desorption reached 78%), than sodium base (maximal desorption 25%).
Copper (Cu) and silver (Ag) occur naturally in the environment but have toxic effects on organisms at elevated concentrations. This paper discussed the removal of Cu and Ag from aqueous solutions ...using biochars obtained at different pyrolysis temperatures. Three biomass sources-sunflower husks (SH), a mixture of sunflower husks and rapeseed pomace (SR) and wood waste (WW)-were pyrolyzed at 300, 400 and 500 °C. Biochars produced at 500 °C exhibited a higher specific surface area, lower variable surface charge and lower contents of surface functional groups than those obtained at 400 or 300 °C. The pseudo-second-order model and intra-particle diffusion (IPD) model well-described the Cu and Ag adsorption kinetics. The Cu adsorption was about 1.48 times slower than the Ag adsorption on the biochars obtained at 500 °C. The model of Langmuir-Freundlich well-described the equilibrium adsorption. Agricultural biochars obtained at >500 °C had a surface with a higher affinity to attract Ag than Cu and were able to remove a larger amount of heavy metals from aqueous media than those prepared at lower pyrolysis temperatures.
The study focused on the adsorption mechanism of two selected pesticides: carboxin and diuron, on goethite and biochar, which were treated as potential compounds of mixed adsorbent. The authors also ...prepared a simple mixture of goethite and biochar and performed adsorption measurements on this material. The adsorbents were characterized by several methods, inter alia, nitrogen adsorption/desorption, Boehm titration, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The adsorption study included kinetics and equilibrium measurements, in the solution containing one or two pesticides simultaneously. The adsorption data were fitted to selected theoretical models (e.g., Langmuir, Freudlich, Redlich–Peterson, pseudo first-order and pseudo second-order equations). Based on the obtained results, it was stated that, among all tested adsorbents, biochar had the highest adsorption capacity relative to both carboxin and diuron. It equaled 0.64 and 0.52 mg/g, respectively. Experimental data were best fitted to the pseudo second-order and Redlich–Peterson models. In the mixed systems, the adsorption levels observed on biochar, goethite and their mixture were higher for diuron and lower for carboxin, compared to those noted in the single solutions. The presented results may enable the development of new mixed adsorbent for remediation of soils polluted with pesticides.
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