Utilization of biochar sorbents for Cd²âº, Zn²âº, and Cu²âº ions separation from aqueous solutions: comparative study.

The objective of this study was to study the utilization of two different woody-derived biochars for Cd(2+), Zn(2+), and Cu(2+) ions separation from aqueous solutions. Physicochemical characterization confirmed the main differences in sorbent surface area and cation-exchange capacity. The maximum cadmium, zinc, and copper sorption capacities were 1.99, 0.97, and 2.50 mg g(-1) for biochar (BC) A; 7.80, 2.23, and 3.65 mg g(-1) for BC B. Sorption processes can be affected by time and pH. The most of sorbed cadmium and zinc were bound on exchangeable fractions and copper oxidizable fractions. Chemical modification and FT-IR analyses confirmed the crucial roles of hydroxyl and mainly carboxyl functional groups in sorption processes of Cd(2+), Zn(2+), and Cu(2+) ions by BC A and BC B. The garden wood rests with leaf mass-derived biochar can be utilized as an effective sorbent for bivalent ions.

Physicochemical Characterization of Cherry Pits-Derived Biochar.

Although the suitability of some biochars for contaminants' sorption separation has been established, not all potential feedstocks have been explored and characterized. Here, we physicochemically characterized cherry pit biochar (CPB) pyrolyzed from cherry pit biomass (CP) at 500 °C, and we assessed their As and Hg sorption efficiencies in aqueous solutions in comparison to activated carbon (AC). The basic physicochemical and material characterization of the studied adsorbents was carried out using pH, electrical conductivity (EC), cation exchange capacity (CEC), concentration of surface functional groups (Boehm titration), and surface area (SA) analysis; elemental C, H, N analysis; and Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). AsO43- anions and Hg2+ cations were selected as model contaminants used to test the sorption properties of the sorption materials. Characterization analyses confirmed a ninefold increase in SA in the case of CPB. The total C concentration increased by 26%, while decreases in the total H and N concentrations were observed. The values of carbonate and ash contents decreased by about half due to pyrolysis processes. The concentrations of surface functional groups of the analyzed biochar obtained by Boehm titration confirmed a decrease in carboxyl and lactone groups, while an increase in phenolic functional groups was observed. Changes in the morphology and surface functionality of the pyrolyzed material were confirmed by SEM-EDX and FTIR analyses. In sorption experiments, we found that the CPB showed better results in the sorption separation of Hg2+ than in the sorption separation of AsO43-. The sorption efficiency for the model cation increased in the order CP < CPB < AC and, for the model anion, it increased in the order CPB < CP < AC.

Biochar from Wood Chips and Corn Cobs for Adsorption of Thioflavin T and Erythrosine B.

Biochars from wood chips (WC) and corn cobs (CC) were prepared by slow pyrolysis and used for sorption separation of erythrosine B (EB) and thioflavin T (TT) in batch experiments. Biochar-based adsorbents were extensively characterized using FTIR, XRD, SEM-EDX, and XPS techniques. The kinetics studies revealed that adsorption on external surfaces was the rate-limiting step for the removal of TT on both WC and CC biochar, while intraparticle diffusion was the rate-limiting step for the adsorption of EB. Maximal experimental adsorption capacities Qmaxexp of TT reached 182 ± 5 (WC) and 45 ± 2 mg g-1 (CC), and EB 12.7 ± 0.9 (WC) and 1.5 ± 0.4 mg g-1 (CC), respectively, thereby indicating a higher affinity of biochars for TT. The adsorption mechanism was found to be associated with π-π interaction, hydrogen bonding, and pore filling. Application of the innovative dynamic approach based on fast-field-cycling NMR relaxometry indicates that variations in the retention of water-soluble dyes could be explained by distinct water dynamics in the porous structures of WC and CC. The obtained results suggest that studied biochars will be more effective in adsorbing of cationic than anionic dyes from contaminated effluents.

Biosorption of Cadmium, Cobalt and Zinc by Moss Rhytidiadelphus squarrosus in the Single and Binary Component Systems.

Biomass of moss Rhytidiadelphus squarrosus was studied as a potential biosorbent for cadmium, cobalt and zinc removal from single and binary solutions. It was shown that solution pH significantly influenced Cd, Co and Zn biosorption. Maximum uptake was reached at pH 5.0-6.0 and negligible biosorption was observed at pH 2.0. Experimental equilibrium biosorption data for cadmium, cobalt and zinc were analysed by the Langmuir and Freundlich isotherm models. The Langmuir isotherm was found to well represent the measured sorption data in single metal systems. The maximum sorption capacities Qmax onto moss biomass were 186 µmol/g for Zn, 173 µmol/g for Cd and 123 µmol/g for Co. Results revealed that the presence of Cd more significantly decreased the sorption of Co in binary Cd-Co mixtures than vice versa. In Cd-Zn binary system, both cadmium and zinc were sorbed with equal efficiency. The competitive Langmuir equations were used to fit the experimental data from the Zn-Cd and Cd-Co binary systems and simple two-dimensional isotherm curves were replaced by three-dimensional sorption isotherm surfaces.

Magnetically Functionalized Moss Biomass as Biosorbent for Efficient Co2+ Ions and Thioflavin T Removal.

Microwave synthesized iron oxide nanoparticles and microparticles were used to prepare a magnetically responsive biosorbent from Rhytidiadelphus squarrosus moss for the rapid and efficient removal of Co2+ ions and thioflavin T (TT). The biocomposite was extensively characterized using Fourier transformed infrared (FTIR), XRD, SEM, and EDX techniques. The magnetic biocomposite showed very good adsorption properties toward Co2+ ions and TT e.g., rapid kinetics, high adsorption capacity (218 µmol g-1 for Co and 483 µmol g-1 for TT), fast magnetic separation, and good reusability in four successive adsorption-desorption cycles. Besides the electrostatic attraction between the oxygen functional moieties of the biomass surface and both Co2+ and TT ions, synergistic interaction with the -FeOH groups of iron oxides also participates in adsorption. The obtained results indicate that the magnetically responsive biocomposite can be a suitable, easily separable, and recyclable biosorbent for water purification.

Iron-impregnated biochars as effective phosphate sorption materials.

A new post-treatment method was applied for improving the sorption efficiency of biochar-based sorbents for anionic forms of phosphorus. The Fe-impregnation through direct hydrolysis of Fe(NO3)3 was used to produce impregnated corn cob- (IBC A), garden wood waste- (IBC B), and wood chip-derived biochars (IBC C). The qualitative and quantitative effects of impregnation process on biochars were confirmed by SEM-EDX, FTIR, and ICP-MS. The analyses revealed increased concentrations of N and thus potential NO3- participation in the phosphate sorption process. Biochar surface area showed a significant decrease after the impregnation process due to the filling of micro- and mesopores with Fe maximum sorption capacity (Q max) increased by a factor of 12-50. The sorption processes of phosphates by IBC A, IBC B, and IBC C were dependent on pH, initial concentration, and time. Speciation analysis and pH-study confirmed the range of pH 4.5-5.5 as optimum values at which most of phosphorus is present in form of mononuclear H2PO4-. Batch sorption experiments showed a significant increase in the sorption capacity for phosphates by Fe impregnation of biochar as well as effectiveness and stability of this treatment. These findings indicate an option for utilizing engineered biochars as tools for the recovery of phosphorus from the aquatic environment.

Monitoring 60Co activity for the characterization of the sorption process of Co2+ ions in municipal activated sludge.

In large volumes produced activated sludges from wastewater treatment plants (WWTPs) with low concentrations of heavy metals can be utilized as agricultural fertilizers and soil conditioners. Increased contents of toxic xenobiotics are limiting factors that affect the utilization of these heterogeneous wastes. The main aim of our paper was to show the utilization of dried activated sludge (DAS) from municipal WWTP as potential Co2+ ions sorbent i.e. for non-agricultural purposes. The radio indicator method by radionuclide 60Co and γ-spectrometry for characterization DAS sorption properties was used. DAS soluble and solid fractions were characterized by biochemical, ETAAS and CEC analysis. The sorption of Co2+ ions by DAS was rapid process and equilibrium was reached within 2 h. Sorption capacity of DAS (Q) increased with the initial concentration of CoCl2 in the range from 100 to 4,000 µmol l-1, reaching 20 and 160 µmol g-1. Obtained Q values were depent on pH value from 2.0 to 8.0. The maximum sorption capacity (Qmax) of DAS at pH 6 calculated from mathematical model of Langmuir adsorption isotherm was 175 ± 9 µmol g-1. FT-IR analyses showed the crucial role of carboxyl functional groups of DAS surfaces on cobalt uptake. For confirmation ion-exchange mechanism in sorption process of Co2+ ions by DAS scanning electron microscopy and EDX analysis were used.