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.

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.

Engineered Pyrogenic Materials as Tools to Affect Arsenic Mobility in Old Mine Site Soil of Mediterranean Region.

The application of pyrogenic materials in immobilization processes of metalloids represents a burning issue in environmental and waste applications and management. The main objective of this study was to characterize the effect of biomass pretreatment by Cu, Fe and Mg blending and pyrolysis temperature on As sorption efficiency as a model of anionic metalloids from model solutions and As immobilization in old mine soil by pyrogenic materials. The physico-chemical characterization of engineered materials produced in slow pyrolysis process at 400 and 700°C from metal-blended hard wood chips (30% w/w) showed increasing of surface areas (1.4-1.8-fold), changes in pH, and more than 50% decrease in total C content. The batch sorption processes of As ions by Cu-modified pyrogenic materials (CuPM), Fe-modified pyrogenic materials (FePM), and Mg-modified pyrogenic materials (MgPM) showed increasing uptake in order CuPM700 (Qmax 2.56 mg g-1) < CuPM400 (Qmax 3.88 mg g-1) < FePM700 (Qmax 5.90 mg g-1) < MgPM700 (Qmax 7.42 mg g-1) < MgPM400 (Qmax 9.59 mg g-1) < FePM400 (Qmax 10.55 mg g-1). Engineered pyrogenic materials produced at 400°C showed higher immobilization effect on soluble As in soil pore water of old mine site soil from Mediterranean area. FePM400 reduced mobility of arsenic > 3.2 times and MgPM400 > 5 times compared to control. Promising pyrogenic material MgPM400 showed immobilization effect also on additional heavy metals (Cd, Cu, Fe, Mn, Pb, Sr, Zn) present in studied soil.

Designing biochar properties through the blending of biomass feedstock with metals: Impact on oxyanions adsorption behavior.

Metal-blending of biomass prior to pyrolysis is investigated in this work as a tool to modify biochar physico-chemical properties and its behavior as adsorbent. Six different compounds were used for metal-blending: AlCl3, Cu(OH)2, FeSO4, KCl, MgCl2 and Mg(OH)2. Pyrolysis experiments were performed at 400 and 700 °C and the characterization of biochar properties included: elemental composition, thermal stability, surface area and pore size distribution, Zeta potential, redox potential, chemical structure (with nuclear magnetic resonance) and adsorption behavior of arsenate, phosphate and nitrate. Metalblending strongly affected biochars' surface charge and redox potential. Moreover, it increased biochars' microporosity (per mass of organic carbon). For most biochars, mesoporosity was also increased. The adsorption behavior was enhanced for all metal-blended biochars, although with significant differences across species: Mg(OH)2-blended biochar produced at 400 °C showed the highest phosphate adsorption capacity (Langmuir Qmax approx. 250 mg g-1), while AlCl3-blended biochar produced also at 400 °C showed the highest arsenate adsorption (Langmuir Qmax approx. 14 mg g-1). Significant differences were present, even for the same biochar, with respect to the investigated oxyanions. This indicates that biochar properties need to be optimized for each application, but also that this optimization can be achieved with tools such as metal-blending. These results constitute a significant contribution towards the production of designer biochars.

Monitoring of methylated naphthalenes in sludge-derived pyrogenic carbonaceous materials.

Methylated analogues of polycyclic aromatic hydrocarbons (PAHs) represent important environmental contaminants produced often at process of feedstock thermochemical conversion. In the present study, we determined and compared levels of 1-methylnaphtalene and 2-methylnaphtalene in municipal sewage sludge (MSS), sludge-derived pyrogenic carbonaceous materials produced at 350 °C (PCM350) and 500 °C (PCM500) in process of slow pyrolysis. The highest extraction efficiency of both aromatic structures from MSS, PCM350 and PCM500 for toluene as extraction agent and 36 h of extraction time was revealed. The total concentrations of 1-methylnaphtalene reached values 8.7 mg/kg for MSS, 14.6 mg/kg for PCM350 and 18.1 mg/kg for PCM500.2-methylnaphtalene was quantified in concentrations 12.5 mg/kg for MSS, 19.3 mg/kg for PCM350 and 23 mg/kg for PCM500. Available levels of 1-methylnaphtalene and 2-methylnaphtalene determined by Tenax resin desorption test during 36 days showed decreasing trend in order PCM500 > PCM350 > MSS. In summary, pyrolysis treatment of sewage sludge can increase total amount of methylated PAHs in produced carbonaceous materials but decrease their available forms. This fact can contribute to global ecotoxicological assessment of organic pollutants in biochars and pyrogenic carbonaceous materials applied in agronomy as soil amendments.

The effect of biochar amendments on phenanthrene sorption, desorption and mineralisation in different soils.

The contamination of soils and waters with organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs), affect a large number of sites worldwide that need remediation. In this context soils amendments can be used to immobilise PAHs while maintaining soil functioning, with biochar being a promising amendment. In this experiment, phenantrene (Phe) was used as a frequent PAH contaminating soils and we studied the effect of three biochars at 1% applications to three different substrates, two agricultural topsoils and pure sand. We evaluated the changes in soil properties, sorption-desorption of Phe, and mineralisation of Phe in all treatments. Phe in pure sand was effectively sorbed to olive pruning (OBC) and rice husk (RBC) biochars, but pine biochar (PBC) was not as effective. In the soils, OBC and RBC only increased sorption of Phe in the silty soil. Desorption was affected by biochar application, RBC and OBC decreased water soluble Phe independently of the soil, which may be useful in preventing leaching of Phe into natural waters. Contrastingly, OBC and RBC slightly decreased the mineralisation of Phe in the soils, thus indicating lower bioavailability of the contaminant. Overall, biochar effects in the two tested soils were low, most likely due to the rather high soil organic C (SOC) contents of 2.2 and 2.8% with Koc values in the same range as those of the biochars. However, OBC and RBC additions can substantially increase adsorption of Phe in soils poor in SOC.

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.

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.

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.