Biochar as a replacement material in advanced separation technologies

Daniel S. Alessi 대한환경공학회 2019 대한환경공학회 학술발표논문집 Vol.2019 No.-

Removal of hexavalent chromium in aqueous solutions using biochar: Chemical and spectroscopic investigations

Rajapaksha, Anushka Upamali,Alam, Md. Samrat,Chen, Ning,Alessi, Daniel S.,Igalavithana, Avanthi Deshani,Tsang, Daniel C.W.,Ok, Yong Sik Elsevier BV 2018 Science of the Total Environment Vol.625 No.-

<P><B>Abstract</B></P> <P>Biochar is an emerging low-cost sorbent used for removing trace metals from water. In this study, we evaluated the removal potential of aqueous hexavalent chromium (Cr(VI)) by biochars produced from soybean (<I>Glycine</I> <I>max</I> L.) and burcucumber (<I>Sicyos angulatus</I> L.) residues. The highest Cr(VI) removal from solution occurred at low pH values (pH2–5), and adsorption decreased approximately tenfold when the pH increased from 2 to 10. Synchrotron-based X-ray absorption spectroscopy (XAS) investigations showed that Cr(VI) species were reduced to trivalent chromium (Cr(III)) at the biochar surface following Cr(VI) adsorption. Linear combination fitting (LCF) of X-ray absorption near edge structure (XANES) data indicated that approximately 90% of the total Cr(VI) (962μM) was reduced to Cr(III). Extended X-ray absorption fine structure (EXAFS) fitting results yielded interatomic chromium (CrCr) distances consistent with the formation of Cr(III) precipitates as Cr(OH)<SUB>3</SUB>. Trivalent chromium is far less soluble than Cr(VI) and typically precipitates as amorphous Cr(III) solids. Thus, biochars produced by soybean and burcucumber residues are a promising technique for both adsorbing and reductively immobilizing Cr(VI) from aqueous solutions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Removal potential of aqueous Cr(VI) by biochar was evaluated. </LI> <LI> The highest Cr(VI) removal occurred at low pH values. </LI> <LI> Cr(VI) species can be reduced to Cr(III) at the biochar surface. </LI> <LI> Biochar properties determine the coordination environment of Cr(III) products. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Selection criteria for oxidation method in total organic carbon measurement

Yoon, GeunSeok,Park, Sang-Min,Yang, Heuiwon,Tsang, Daniel C.W.,Alessi, Daniel S.,Baek, Kitae Elsevier 2018 CHEMOSPHERE - Vol.199 No.-

<P><B>Abstract</B></P> <P>During the measurement of total organic carbon (TOC), dissolved organic carbon is converted into CO<SUB>2</SUB> by using high temperature combustion (HTC) or wet chemical oxidation (WCO). However, the criteria for selecting the oxidation methods are not clear. In this study, the chemical structures of organic material were considered as a key factor to select the oxidation method used. Most non-degradable organic compounds showed a similar oxidation efficiency in both methods, including natural organic compounds, dyes, and pharmaceuticals, and thus both methods are appropriate to measure TOC in waters containing these compounds. However, only a fraction of the carbon in the halogenated compounds (perfluorooctanoic acid and trifluoroacetic acid) were oxidized using WCO, resulting in measured TOC values that are considerably lower than those determined by HTC. This result is likely due to the electronegativity of halogen elements which inhibits the approach of electron-rich sulfate radicals in the WCO, and the higher bond strength of carbon-halogen pairs as compared to carbon-hydrogen bonds, which results in a lower degree of oxidation of the compounds. Our results indicate that WCO could be used to oxidize most organic compounds, but may not be appropriate to quantify TOC in organic carbon pools that contain certain halogenated compounds.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Concentration of organic matter is not suitable to determine oxidation method. </LI> <LI> Chemical structure is a key factor determining oxidation of organic matter. </LI> <LI> Wet chemical oxidation oxidized partially halogenated compounds. </LI> </UL> </P>

Risk evaluation of biochars produced from Cd-contaminated rice straw and optimization of its production for Cd removal

Shen, Zhengtao,Fan, Xiaoliang,Hou, Deyi,Jin, Fei,O'Connor, David,Tsang, Daniel C.W.,Ok, Yong Sik,Alessi, Daniel S. Pergamon Press 2019 Chemosphere Vol. No.

<P><B>Abstract</B></P> <P>Based on the “waste-treat-waste” concept, biochars were produced from cadmium (Cd)-contaminated rice straw (CRSBs) at 300, 500, and 700 °C (CRSB300, CRSB500, and CRSB700). The risks of the Cd remaining in CRSBs were evaluated and the optimal biochar pyrolysis temperature for Cd removal was investigated. It was observed that 41% of the total Cd in the raw rice straw was exchangeable, which may pose significant risks to crops and humans. Pyrolyzing at 300 °C did not significantly alter the Cd fractions, while the exchangeable fraction of Cd greatly dropped to 5.79% at 500 °C and further to 2.12% at 700 °C. Increasing the highest pyrolysis temperature resulted in CRSBs with higher pH values, greater surface area, and smaller pore sizes, thus providing more rapid and efficient removal of Cd from aqueous solutions. For Cd removal tests, increasing pyrolysis temperature (300–700 °C) increased the total (24.8–55.1 mg/g) and non-exchangeable (18.9–52.8 mg/g) Cd concentrations immobilized on the CRSBs and significantly decreased the exchangeable Cd fraction (23.7%–4.85%). It is suggested based on the study from aqueous solutions that CRSB700 was the most suitable for the remediation of Cd contaminated soil on site due to the lowest risks of remained Cd from feedstock, fastest and highest Cd removal, and most stable immobilization of Cd.</P> <P><B>Highlights</B></P> <P> <UL> <LI> 41% of Cd in raw rice straw was exchangeable, posing great environmental risks. </LI> <LI> Pyrolyzing at 300 °C did not significantly alter Cd fractions remained in biochar. </LI> <LI> Exchangeable fraction of Cd dropped to 5.79% at 500 °C and to 2.12% at 700 °C. </LI> <LI> Increasing temperature decreased exchangeable Cd fraction immobilized on biochar. </LI> <LI> CRSB700 has the fastest and highest Cd removal, and most stable Cd immobilization. </LI> </UL> </P>

Thermodynamic Analysis of Nickel(II) and Zinc(II) Adsorption to Biochar

Alam, Md. Samrat,Gorman-Lewis, Drew,Chen, Ning,Flynn, Shannon L.,Ok, Yong Sik,Konhauser, Kurt O.,Alessi, Daniel S. American Chemical Society 2018 Environmental science & technology Vol.52 No.11

<P>While numerous studies have investigated metal uptake from solution by biochar, few of these have developed a mechanistic understanding of the adsorption reactions that occur at the biochar surface. In this study, we explore a combined modeling and spectroscopic approach for the first time to describe the molecular level adsorption of Ni(II) and Zn(II) to five types of biochar. Following thorough characterization, potentiometric titrations were carried out to measure the proton (H<SUP>+</SUP>) reactivity of each biochar, and the data was used to develop protonation models. Surface complexation modeling (SCM) supported by synchrotron-based extended X-ray absorption fine structure (EXAFS) was then used to gain insights into the molecular scale metal-biochar surface reactions. The SCM approach was combined with isothermal titration calorimetry (ITC) data to determine the thermodynamic driving forces of metal adsorption. Our results show that the reactivity of biochar toward Ni(II) and Zn(II) directly relates to the site densities of biochar. EXAFS along with FT-IR analyses, suggest that Ni(II) and Zn(II) adsorption occurred primarily through proton-active carboxyl (−COOH) and hydroxyl (−OH) functional groups on the biochar surface. SCM-ITC analyses revealed that the enthalpies of protonation are exothermic and Ni(II) and Zn(II) complexes with biochar surface are slightly exothermic to slightly endothermic. The results obtained from these combined approaches contribute to the better understanding of molecular scale metal adsorption onto the biochar surface, and will facilitate the further development of thermodynamics-based, predictive approaches to biochar removal of metals from contaminated water.</P> [FIG OMISSION]</BR>

Stability of heavy metals in soil washing residue with and without biochar addition under accelerated ageing

Shen, Zhengtao,Hou, Deyi,Zhao, Bin,Xu, Wendi,Ok, Yong Sik,Bolan, Nanthi S.,Alessi, Daniel S. Elsevier 2018 Science of the Total Environment Vol.619 No.-

<P><B>Abstract</B></P> <P>Soil washing residue (SWR), which typically concentrates the washed toxic metals and is comprised of high contents of clay particles, may pose risks to the surrounding environment. This study aims to simulate accelerated ageing to assess the stability of selected metals (Cd<SUP>2+</SUP> (132mg/kg), Cu<SUP>2+</SUP> (248mg/kg) and Pb<SUP>2+</SUP> (3470mg/kg)) in a SWR (89.68% of clay) with and without biochar treatment. The soil was incubated under constant moisture and wet-dry cycles (accelerated ageing), respectively, and the mobility and fractions of heavy metals in the soils with and without biochar treatment were examined. Under the constant moisture condition, biochar addition at 5% w/w reduced the leached Cd<SUP>2+</SUP> (by 1.81%) and Cu<SUP>2+</SUP> (by 8.70%) from SWR at day 1 and the leached Cu<SUP>2+</SUP> (by 51.08%) and Pb<SUP>2+</SUP> (by 25.36%) from SWR at day 14; however, the leached metals in the TCLP solution from the biochar-amended soils still exceed the regulatory limits (1mg/L for Cd<SUP>2+</SUP>, 5mg/L for Pb<SUP>2+</SUP>, no regulatory limits for Cu<SUP>2+</SUP>). Conversely, accelerated ageing (14days) significantly increased the fractions of exchangeable Cd<SUP>2+</SUP> (from 3.63–3.94% to 6.21–6.29%) and Pb<SUP>2+</SUP> (from 0.025–0.027% to 0.034–0.041%) as well as the TCLP leachabilities of Cd<SUP>2+</SUP> (from 2.91–3.28% to 3.46–3.73%), Cu<SUP>2+</SUP> (from 0.08–0.10% to 0.03–0.06%) and Pb<SUP>2+</SUP> (from 0.25–0.35% to 0.52–0.57%) in the soils, as compared with those incubated under constant moisture, regardless of biochar addition. This study reveals challenges associated with stabilising SWR due to the presence of residual fine-grained particles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cd<SUP>2+</SUP> and Pb<SUP>2+</SUP> in soil washing residue (SWR) exceeds TCLP regulation limit. </LI> <LI> Heavy metal mobility in SWR was reduced by biochar addition. </LI> <LI> Accelerated ageing mobilised heavy metals in SWR regardless of biochar addition. </LI> <LI> Accelerated ageing show SWR poses long-term risks to the environment. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Modified sequential extraction for biochar and petroleum coke: Metal release potential and its environmental implications

von Gunten, Konstantin,Alam, Md. Samrat,Hubmann, Magdalena,Ok, Yong Sik,Konhauser, Kurt O.,Alessi, Daniel S. Elsevier 2017 Bioresource technology Vol.236 No.-

<P><B>Abstract</B></P> <P>A modified Community Bureau of Reference (CBR) sequential extraction method was tested to assess the composition of untreated pyrogenic carbon (biochar) and oil sands petroleum coke. Wood biochar samples were found to contain lower concentrations of metals, but had higher fractions of easily mobilized alkaline earth and transition metals. Sewage sludge biochar was determined to be less recalcitrant and had higher total metal concentrations, with most of the metals found in the more resilient extraction fractions (oxidizable, residual). Petroleum coke was the most stable material, with a similar metal distribution pattern as the sewage sludge biochar. The applied sequential extraction method represents a suitable technique to recover metals from these materials, and is a valuable tool in understanding the metal retaining and leaching capability of various biochar types and carbonaceous petroleum coke samples.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Modified four step sequential extraction method suitable for pyrolyzed materials. </LI> <LI> Untreated biochar may easily release alkaline earth and transition metals. </LI> <LI> Wood biochar releases metals more readily than does sewage sludge biochar. </LI> </UL> </P>

Effect of dissolved organic carbon from sludge, Rice straw and spent coffee ground biochar on the mobility of arsenic in soil

Kim, Hye-Bin,Kim, Seon-Hee,Jeon, Eun-Ki,Kim, Do-Hyung,Tsang, Daniel C.W.,Alessi, Daniel S.,Kwon, Eilhann E.,Baek, Kitae Elsevier 2018 The Science of the total environment Vol.636 No.-

<P><B>Abstract</B></P> <P>To date, studies on the mobility of arsenic (As) in soil amended with biochar have primarily relied on broad empirical observations, resulting in a gap between the behavior of As in amended soil and the chemical mechanisms controlling that behavior. This study focuses on the influence of abiotic factors in As mobility in As-contaminated soils amended with biochar. In order to understand the leaching of DOC and phosphate across a range of biomass feedstock and pyrolysis temperature, rice straw and granular sludge from an anaerobic digester were pyrolyzed at 300, 550, and 700 °C, and subjected to leaching studies by mixing air dried soil with 10 wt% of biochar at a soil: water ratio of 1:1(w/v). The concentration of DOC in the presence of granular sludge biochar and rice straw biochar increased from 190 mg L<SUP>−1</SUP> to 2605 mg L<SUP>−1</SUP> and 1192 mg L<SUP>−1</SUP>, respectively, which considerable accelerated the mobilization of Fe and As. More specifically, DOC drove the reduction of Fe(III) to Fe(II). Our results suggest enhanced release of As via the reductive dissolution of iron oxides, including by the chelating-enhanced dissolution of Fe oxides, and competitive desorption by DOC and phosphate from biochar. The influence of DOC and phosphate was further evaluated using realistic application amounts (1, 3, and 5 wt%) of biochars derived from pyrolysis of granular sludge, rice straw and spent coffee ground at 300 and 550 °C. The results from these experiments further confirm that DOC is a key factor for influencing the mobility of As in the amendment of biochar to As-contaminated soil, which indicates that biochar having low levels of leachable carbon should be amended to As-contaminated soils, and with caution.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dissolved organic carbon from biochar increased mobility of As in soil. </LI> <LI> Biochar enhanced reductive dissolution of Fe oxides in soil. </LI> <LI> Dissolved organic carbons extract Fe via chelating enhanced dissolution. </LI> <LI> Phosphate enhanced As mobility via competitive desorption </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Application of surface complexation modeling to trace metals uptake by biochar-amended agricultural soils

Alam, Md. Samrat,Swaren, Logan,von Gunten, Konstantin,Cossio, Manuel,Bishop, Brendan,Robbins, Leslie J.,Hou, Deyi,Flynn, Shannon L.,Ok, Yong Sik,Konhauser, Kurt O.,Alessi, Daniel S. Elsevier 2018 Applied geochemistry Vol.88 No.1

<P><B>Abstract</B></P> <P>Biochar has emerged as a useful amendment to release nutrients into agricultural soil, to increase crop productivity, and as a sorbent to remediate metals and organics contamination. Since soils have heterogeneous physical properties across a given crop field, and even over a growing season, it is imperative to select the most appropriate biochar for the intended purpose and in defining the amendment level. In this study, we investigate the adsorption of Cd(II) and Se(VI) as model pollutant cations and anions, respectively, to two agricultural soils amended with a wood pin chip biochar (WPC). The proton reactivity of each sorbent was determined by potentiometric titration, and single-metal, single-sorbent experiments were conducted as a function of pH. The resulting data were modeled using a non-electrostatic surface complexation modeling (SCM) approach to determine the proton and metal binding constants and surface functional group concentrations of each soil and WPC. The SCM approach is a considerable advance over empirical modeling approaches because SCM models can account for changes in pH, ionic strength, temperature, and metal-to-sorbent ratio that may happen over the course of a growing season. The constants derived from the single-metal, single-sorbent experiments were then used to predict the extent of metal adsorption in more complex mixtures of Cd, Se, soil and WPC. Overall the SCM approach was successful in predicting metal distribution in multi-component mixtures. In cases where the predictions were poorer than expected, we identify reasons and discuss future experiments needed to further the application of SCM to sorbent mixtures containing biochar.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cd(II) and Se(VI) adsorption to biochar, soils and their admixtures is tested as a function of pH. </LI> <LI> Surface complexation modeling is applied to biochar-amended soils for the first time. </LI> <LI> Potential impacts of metal-DOC complexes is explored. </LI> <LI> Cd(II) and Se(VI) adsorption to biochar-soil mixtures is generally well-predicted by models. </LI> <LI> Surface complexation models are a promising alternative to empirical adsorption models in the systems tested. </LI> </UL> </P>