Comparison of Monovalent and Divalent Ions Removal from Aqueous Solutions Using Agricultural Waste Biochars Prepared at Different Temperatures-Experimental and Model Study

Use of selected amendments for reducing metal mobility and ecotoxicity in contaminated bottom sediments

The aims of the study were 1) to assess the suitability of selected amendments for reducing the mobility of metals in sediments by evaluating their effects on metal sorption capacity, and 2) to assess the ecotoxicity of sediment/amendment mixtures. Three different amendments were tested: cellulose waste, biochar, and dolomite. The efficiency of metal immobilization in mixtures was dependent on pH, which increased with concentrations of amendment. The higher negative charge observed for dolomite and cellulose waste corresponded with greater attraction of cations and enhanced metal sorption. For cellulose waste, the highest values of the Q parameter were attributed to the presence of OH groups, which corresponded with the highest immobilization of metals. Biochar reduced the negative surface charge, which highlights the importance of additional factors such as high specific surface area and volume of pores in metal immobilization. All amendments increased the SSA and VN2, indicating a higher number of sorption sites for metal immobilization. Most bioassays established a reduction of the ecotoxicity for amendments. Mixtures with dolomite (25%, 45% doses) and biochar (45% dose) were low toxic. Mixtures with cellulose waste were toxic or highly toxic. The mobility of metals from contaminated sediments can be limited by reused industry side products, which could contribute to further closing the circular economy loop.

Assessment of agricultural waste biochars for remediation of degraded water-soil environment: Dissolved organic carbon release and immobilization of impurities in one- or two-adsorbate systems

This paper presents a method of agricultural waste management - the production of two biochars (BC) from potato and raspberry stems. It defines the potential of these materials for remediation of degraded water and soil environments. The performed study included analyses of BC physicochemistry, dissolved organic carbon (DOC) release and ability to immobilize copper (Cu), tetracycline (TC) and carboxin (CB) in one- and two-adsorbate systems. The BCs were obtained with pyrolysis at 600 °C for 30 min in a nitrogen atmosphere. Their DOC was predominantly constituted of substances with large molecular weights and high aromaticity, meaning that both BCs can be safely applied as soil additives. Potato-biochar (P-BC) had a more developed surface than raspberry-biochar (R-BC). The specific surface area (S_BET) of P-BC was 122 m²/g, whilst of R-BC was 87 m²/g. As a result, the efficiency of impurity adsorption in the one-adsorbate systems was higher for P-BC (61.75% for Cu, 73.84% for TC, and 54.43% for CB). In the two-adsorbate systems, organic impurities improved the immobilization of heavy metal ions on BCs. The efficiency of Cu adsorption on P-BC when TC was present was 88.29%. Desorption of Cu from BC was highest using HCl, whilst that of TC and CB was highest using NaOH. Maximum desorption was observed in a two-adsorbate system with TC + CB (up to 63.6% for TC). These results confirmed that potato and raspberry stems can be used to produce highly effective BCs with large application potential, especially for remediation of degraded soils and polluted waters.

Removal of Copper(II) from Aqueous Environment Using Silk Sericin-Derived Carbon

Sericin is a by-product of the silk industry. Its recycling contributes to environmental protection and the sustainable development of the cocoon silk industry. In this paper, on the basis of realizing sericin enrichment in solution, the Cu(II) adsorption capacities of sericin-derived carbon (SC), prepared at different pyrolysis temperatures, were studied. SC was characterized using scanning electron microscopy (SEM) and the zeta potential. The effects of the initial concentration of Cu(II), pH, adsorption temperature, and contact time on the adsorption process were evaluated, followed by an investigation of the mechanism of Cu(II) adsorption by SC. The results showed that SC has a porous structure that provides sites for Cu(II) adsorption. The maximum adsorption capacity of Cu(II) onto SC1050, 17.97 mg/g, was obtained at an adsorption temperature of 35 °C and a pH of 5.5. In addition, the pseudo-second-order kinetic model and Langmuir isotherm model correctly described the adsorption process of Cu(II) onto SC1050. Therefore, SC can act as a potential adsorbent for removing Cu(II) from water. This study helps promote the effective use of cocoon silk resources.

The Physical Chemistry and Chemical Physics (PCCP) Section of the International Journal of Molecular Sciences in Its Publications: The First 300 Thematic Articles in the First 3 Years

The Physical Chemistry and Chemical Physics Section (PCCP Section) is one of the youngest among the sections of the International Journal of Molecular Sciences (IJMS)—the year 2021 will only mark three years since its inception [...]

Comparison of lead(II) ions accumulation and bioavailability on the montmorillonite and kaolinite surfaces in the presence of polyacrylamide soil flocculant

Heavy metals, such as Pb(II), Cd(II), Hg(II), do not degrade like organic compounds and remain in soil for a long time. The presence of organic, mineral or polymeric substances (such as polyacrylamides) may contribute to the accumulation and immobilization of toxic metals in poorly absorbable form for living organisms. The main aim of the study was to compare the effectiveness of lead(II) ions immobilization on the layered aluminosilicate surfaces in the anionic polyacrylamide presence. The effectiveness of Pb(II) adsorption was tested depending on metal cation concentration, content of dissociable groups in added flocculant as well as internal structure of clay mineral. The desorption tests of heavy metal ions were performed by the use of water and EDTA (ethylenediaminetetraacetic acid). By means of measurements of suspension stability and aggregate size formed in the studied systems, the flocculating ability of anionic polyacrylamide was checked. The electrokinetic parameters of mineral particles, i.e. surface charge density and electrokinetic potential, without and with individual adsorbates were also determined. It has been shown that the Pb cations adsorbed amount and the effectiveness of their immobilization strongly depends on the polyacrylamide presence in the system and the internal structure of aluminosilicate.

Simultaneous Removal of Pb2+ and Zn2+ Heavy Metals Using Fly Ash Na-X Zeolite and Its Carbon Na-X(C) Composite

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%).