Risk mitigation by waste-based permeable reactive barriers for groundwater pollution control at e-waste recycling sites

Beiyuan, J.,Tsang, D. C.,Yip, A. C.,Zhang, W.,Ok, Y. S.,Li, X. D. Springer Science + Business Media 2017 Environmental geochemistry and health Vol.39 No.1

<P>Permeable reactive barriers (PRBs) have proved to be a promising passive treatment to control groundwater contamination and associated human health risks. This study explored the potential use of lowcost adsorbents as PRBs media and assessed their longevity and risk mitigation against leaching of acidic rainfall through an ewaste recycling site, of which Cu, Zn, and Pb were the major contaminants. Batch adsorption experiments suggested a higher adsorption capacity of inorganic industrial byproducts [acid mine drainage sludge (AMDS) and coal fly ash (CFA)] and carbonaceous recycled products [food waste compost (FWC) and woodderived biochar] compared to natural inorganic minerals (limestone and apatite). Continuous leaching tests of sand columns with 10 wt% lowcost adsorbents were then conducted to mimic the field situation of acidic rainfall infiltration through ewastecontaminated soils (collected from Qingyuan, China) by using synthetic precipitation leaching procedure (SPLP) solution. In general, Zn leached out first, followed by Cu, and finally delayed breakthrough of Pb. In the worstcase scenario (e. g., at initial concentrations equal to 50fold of average SPLP result), the columns with limestone, apatite, AMDS, or biochar were effective for a relatively short period of about 20-40 pore volumes of leaching, after which Cu breakthrough caused noncancer risk concern and laterstage Pb leaching considerably increased both noncancer and lifetime cancer risk associated with portable use of contaminated water. In contrast, the columns with CFA or FWC successfully mitigated overall risks to an acceptable level for a prolonged period of 100-200 pore volumes. Therefore, with proper selection of lowcost adsorbents (or their mixture), wastebased PRBs is a technically feasible and economically viable solution to mitigate human health risk due to contaminated groundwater at ewaste recycling sites.</P>

Integrating EDDS-enhanced washing with low-cost stabilization of metal-contaminated soil from an e-waste recycling site

Beiyuan, J.,Tsang, D.C.W.,Ok, Y.S.,Zhang, W.,Yang, X.,Baek, K.,Li, X.D. Pergamon Press 2016 CHEMOSPHERE - Vol.159 No.-

While chelant-enhanced soil washing has been widely studied for metal extraction from contaminated soils, there are concerns about destabilization and leaching of residual metals after remediation. This study integrated 2-h soil washing enhanced by biodegradable ethylenediaminedisuccinic acid (EDDS) and 2-month stabilization using agricultural waste product (soybean stover biochar pyrolyzed at 300 and 700 <SUP>o</SUP>C), industrial by-product (coal fly ash (CFA)), and their mixture. After integration with 2-month stabilization, the leachability and mobility of residual metals (Cu, Zn, and Pb) in the field-contaminated soil were significantly reduced, especially for Cu, in comparison with 2-h EDDS washing alone. This suggested that the metals destabilized by EDDS-washing could be immobilized by subsequent stabilization with biochar and CFA. Moreover, when the remediation performance was evaluated for phytoavailability and bioaccessibility, prior EDDS washing helped to achieve a greater reduction in the bioavailable fraction of metals than sole stabilization treatment. This was probably because the weakly-bound metals were first removed by EDDS washing before stabilization. Both individual and combined applications of biochar and CFA showed comparable effectiveness regardless of the difference in material properties, possibly due to the high level of amendments (150 ton ha<SUP>-1</SUP>). Based on the mobility and bioaccessibility results, the estimated human health risk (primarily resulting from Pb) could be mitigated to an acceptable level in water consumption pathway or reduced by half in soil ingestion pathway. These results suggest that an integration of EDDS washing with soil stabilization can alleviate post-remediation impacts of residual metals in the treated soil.

Interactions of food waste compost with metals and metal-chelant complexes during soil remediation

Beiyuan, Jingzi,Tsang, Daniel C.W.,Bolan, Nanthi S.,Baek, Kitae,Ok, Yong Sik,Li, Xiang-Dong Elsevier 2018 JOURNAL OF CLEANER PRODUCTION Vol.192 No.-

<P><B>Abstract</B></P> <P>For removing potentially toxic elements (PTEs) from field-contaminated soils, cost-effective soil remediation has been a worldwide concern. As one of the widely employed techniques, chelant-enhanced phytoremediation can remove PTEs with marginal impact on the soil properties, yet the newly formed metal-chelant complexes cannot be completely captured and extracted by the plants. This arouses concerns about downstream migration and secondary contamination of the metal-chelant complexes and free chelant. Organic amendments, such as food waste compost (FWC), may stabilize metals and/or metal-chelant complexes, improve soil properties and plant growth, and reduce waste volume. Therefore, FWC may provide a solution for the migration of metal-chelant complexes and free chelant. Two chelants were selected in this study: EDTA (ethylene-diaminetetraacetic-acid) and its biodegradable isomer EDDS ([<I>S,S</I>]-ethylenediaminedisuccinic acid). The interactions between FWC and metals, metal-EDTA/metal-EDDS complexes in a field-contaminated soil (mainly by Cu, Zn, and Pb) were investigated. Batch adsorption isotherms indicated a strong adsorption capacity of FWC for uncomplexed Cu, Zn, and Pb ions. Significant adsorption of Pb-EDDS (∼100%), Zn-EDDS (>77%), and Cu-EDTA (36–76%) complexes on the FWC was found at apparent equilibrium. The adsorption capacity of Cu-EDDS (32–38%), Pb-EDTA (∼20%), and Zn-EDTA (∼0%) complexes was limited. However, the co-existence of FWC and EDDS increased the mobilization of Cu and Zn, while the co-existence of FWC and EDTA reduced the available amounts of Cu and Pb in solution. Metal speciation calculation showed that nearly all extracted Cu, Zn, and Pb were complexed with chelants in the solution, while notable amount of dissolved Fe (but not Al and Ca) was associated with dissolved organic matter. In this study, FWC can be useful for minimizing the unintended leaching of Cu- and Pb-EDTA complexes in EDTA-enhanced phytoremediation, yet it might be less suitable for the case of EDDS. A novel integration of recycled waste can enhance the effectiveness of sustainable remediation of contaminated soils.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Large amounts of dissolved organic matter released from food waste compost (FWC). </LI> <LI> Cu, Zn, and Pb ions significantly adsorbed to FWC. </LI> <LI> Yet metal-EDDS/EDTA complexes showed diverse adsorption behaviours on FWC. </LI> <LI> Cu-EDDS complexes can be adsorbed to FWC yet the Cu mobility increased with FWC. </LI> <LI> FMC-derived DOM mitigated the EDTA-induced solubilization of Cu and Pb in soil. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Combined application of EDDS and EDTA for removal of potentially toxic elements under multiple soil washing schemes

Beiyuan, Jingzi,Tsang, Daniel C.W.,Valix, Marjorie,Baek, Kitae,Ok, Yong Sik,Zhang, Weihua,Bolan, Nanthi S.,Rinklebe, Jö,rg,Li, Xiang-Dong Elsevier 2018 CHEMOSPHERE - Vol.205 No.-

<P><B>Abstract</B></P> <P>Chelant-enhanced soil washing, such as EDTA (ethylenediaminetetraacetic acid) and biodegradable EDDS ([<I>S,S</I>]-ethylene-diamine-disuccinic acid), has been widely studied, however, EDTA is persistent under natural conditions while EDDS has a low efficiency for Pb extraction. Therefore, we investigated the efficacy of mixed chelants (EDDS and EDTA mixture at 1:1 M ratio) for the removal of Cu, Zn, and Pb from a field-contaminated soil using various washing schemes (multi-pulse, step-gradient chelant, and continuous washing schemes). Speciation modelling of the target metals, mineral elements, and EDDS/EDTA was performed, while the leachability and bioaccessibility of residual metals in the treated soils were also assessed. Our results suggested that the combined use of EDDS and EDTA reached equivalent extraction efficiency of the target metals as EDTA, i.e., 50% reduction in the dosage of EDTA was made possible. This was accomplished by selective extraction of Cu by EDDS and Pb by EDTA, which was supported by the results of speciation calculation. Multi-pulse washing scheme with intermittent water rinsing steps removed entrapped metal-chelant complexes and free chelants, therefore reducing the leachability and bioaccessibility of residual metals in the treated soils. Step-gradient chelant washing with the maximum dosage of chelants in the first washing step only achieved marginal improvement but undesirably promoted Pb bioaccessibility. Continuous washing for 24 h enhanced metal extraction but promoted mineral dissolution, together with a large amount of uncomplexed chelants and increase in Cu leachability. Thus the combined use of EDDS and EDTA in multi-pulse washing is recommended for further studies.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mixture of EDDS and EDTA extracted comparable amount of PTEs as EDTA washing. </LI> <LI> Mixed chelants allowed complementary metal complexation and higher efficiency. </LI> <LI> Multi-pulse washing better utilized chelants and reduced leachability/bioaccessibility. </LI> <LI> Step-gradient chelant dosage hardly improved extraction but increased bioaccessible Pb. </LI> <LI> Continuous washing increased amounts of uncomplexed chelants and dissolved minerals. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Chelant-enhanced washing of CCA-contaminated soil: Coupled with selective dissolution or soil stabilization

Beiyuan, Jingzi,Lau, Abbe Y.T.,Tsang, Daniel C.W.,Zhang, Weihua,Kao, Chih-Ming,Baek, Kitae,Ok, Yong Sik,Li, Xiang-Dong Elsevier 2018 Science of the Total Environment Vol.612 No.-

<P><B>Abstract</B></P> <P>Remediation of CCA-contaminated soil (Cr, Cu, and As) by biodegradable chelant-enhanced washing (EDDS, <I>S,S</I>-ethylene-diamine-disuccinic-acid) needs further enhancement. This study investigated the effectiveness of coupling with pre-treatment by selective dissolution and post-treatment by soil amendments, respectively. Three groups of reagents (reductants, alkaline solvents, and organic ligands) were adopted in the pre-treatment to dissolve the oxide minerals before EDDS extraction. In the post-treatment, soil amendments (coal fly ash (CFA), acid mine drainage sludge (AMDS), green waste compost (GWC)), and their mixtures) were used for a 2-month stabilization after 2-h EDDS washing. Multi-endpoint evaluation was performed by assessing the chemical state, leachability, mobility, bioaccessibility, and plant-availability of residual metal(loid)s as well as the cytotoxicity, enzyme activities, and available nutrients of the treated soils. Pre-treatment by dithionite-citrate-bicarbonate significantly enhanced extraction efficiency, but also increased the leachability of As and Cr and bioaccessibility of Cr in the treated soils. While sodium hydroxide removed the majority of As without increasing its leachability and bioaccessibility, it increased the cytotoxicity and inhibited the acid phosphatase activity. Post-treatment with AMDS and CFA effectively controlled the mobility and leachability of residual As and Cr after EDDS washing. However, destabilized Cu was only marginally immobilized by GWC due to strong Cu-EDDS complexation. The bioaccessibility and phytoavailability of Cu was primarily reduced by EDDS washing, while those of As and Cr could be attenuated by AMDS and CFA. This study indicates that coupling chemical extraction with subsequent soil amendment plays complementary roles in mitigating effects of residual metal(loid)s and improving environmental quality.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Selective dissolution improved the removal efficiency of Cr, Cu, and As. </LI> <LI> Leachability and bioaccessibility of residual metal(loid)s were increased. </LI> <LI> NaOH washing boosted cytotoxicity and inhibited acid phosphatase activity. </LI> <LI> Mobility and leachability of residual metal(loid)s were curbed by CFA and AMDS. </LI> <LI> In contrast, bioaccessibility and plant-availability were reduced only by EDDS. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Facilitating Remediation of E-waste Contaminated Soil by Mixed Chelants and Different Washing Schemes

Jingzi Beiyuan,Nick Siu,Dan Tsang 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6

Interactions of Food Waste Compost with Metals and Metal-Chelant Complexes during Soil Remediation

Jingzi Beiyuan,Josie Wu,Dan Tsang 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6

A combination of ferric nitrate/EDDS-enhanced washing and sludge-derived biochar stabilization of metal-contaminated soils

Yoo, Jong-Chan,Beiyuan, Jingzi,Wang, Lei,Tsang, Daniel C.W.,Baek, Kitae,Bolan, Nanthi S.,Ok, Yong Sik,Li, Xiang-Dong Elsevier 2018 Science of the Total Environment Vol.616 No.-

<P><B>Abstract</B></P> <P>In this study, soil washing and stabilization as a two-step soil remediation strategy was performed to remediate Pb- and Cu-contaminated soils from shooting range and railway sites. Ferric nitrate (Fe(NO<SUB>3</SUB>)<SUB>3</SUB>) and [<I>S,S</I>]-ethylenediamine disuccinate (EDDS) were used as washing agents, whereas three types of sludge-derived biochars and phosphogypsum were employed as soil stabilizers. While Fe(NO<SUB>3</SUB>)<SUB>3</SUB> extracted larger amounts of metals compared to EDDS (84% Pb and 64% Cu from shooting range soil; 30% Pb and 40% Cu from railway site soil), it caused severe soil acidification. Both Fe(NO<SUB>3</SUB>)<SUB>3</SUB> and EDDS washing enhanced the mobility of residual metals in the two soils, which in most cases could be mitigated by subsequent 2-month stabilization by sludge-derived biochars or phosphogypsum. By contrast, the metal bioaccessibility could only be reduced by soil washing. Nutrient-rich sludge-derived biochar replenished available P and K in both soils, whereas Fe(NO<SUB>3</SUB>)<SUB>3</SUB> washing provided available nitrogen (N). Soil amendment enhanced acid phosphatase activity but marginally improved soil dehydrogenase and urease activity in the treated soils, possibly due to the influence of residual metals. This study supported the integration of soil washing (by Fe(NO<SUB>3</SUB>)<SUB>3</SUB> or EDDS) with soil stabilization (by sludge-derived biochars or phosphogypsum) for accomplishing the reduction of metal mobility and bioaccessibility, while restoring the environmental quality of the treated soils.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fe(NO<SUB>3</SUB>)<SUB>3</SUB> washing significantly removed Pb from shooting range and railway soils. </LI> <LI> Biochars neutralized acidic soil pH resulting from Fe(NO<SUB>3</SUB>)<SUB>3</SUB> washing. </LI> <LI> Phosphogypsum immobilized residual Pb by forming insoluble PbSO<SUB>4</SUB> precipitates. </LI> <LI> Sludge-derived biochars reduced metal mobility and enhanced soil quality. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Pine sawdust biomass and biochars at different pyrolysis temperatures change soil redox processes

Awad, Yasser Mahmoud,Ok, Yong Sik,Abrigata, Jens,Beiyuan, Jingzi,Beckers, Felix,Tsang, Daniel C.W.,Rinklebe, Jö,rg Elsevier BV 2018 Science of the Total Environment Vol. No.

<P><B>Abstract</B></P> <P>To date, no investigation has been carried out to explore the effects of biochars produced at different pyrolysis temperatures on the dynamics of redox potential (<I>E</I> <SUB>H</SUB>) and pH in a contaminated floodplain soil. Thus, we aimed to quantify the dynamics of <I>E</I> <SUB>H</SUB> and pH in contaminated flooded soils treated with 70tha<SUP>−1</SUP> of pine sawdust biomass (S&BM) and biochars pyrolyzed at 300°C (S&BC300) and 550°C (S&BC550) and pre-incubated for 105days in an automated biogeochemical microcosm system. Microbial community composition was also determined via analyzing phospholipid fatty acid (PLFA).We found that BC300 and BC550 treatments substantially decreased (3–6.5%) and BM increased (~37%) the mean of soil <I>E</I> <SUB>H</SUB> compared to the untreated contaminated soil (CS).·The largest <I>E</I> <SUB>H</SUB> decline in S&BC550 was at the rate of −80mVh<SUP>−1</SUP> at 10h while it was observed at 25h in S&BC300 and 20–25h in S&BM or CS, respectively. At high <I>E</I> <SUB>H</SUB>, a higher total PLFA biomass and microbial groups in the CS (71–87%) were found in comparison to treated soils. Higher aromaticity and ash content in BC550 than BC300 and BM led to the greater PLFA biomass and microbial groups which contributed to higher capacity of accepting and donating electrons in soil slurry and were probably one reason for the largest decrease in <I>E</I> <SUB>H</SUB>. Pine sawdust biomass and BCs have a noticeable influence in soil biogeochemical processes relevant to fluctuating redox conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> First study of the effects of biochars on soil redox potential (<I>E</I> <SUB>H</SUB>) and pH </LI> <LI> The most rapid <I>E</I> <SUB>H</SUB> change per hour was in soil treated with biochar made at 550°C. </LI> <LI> This <I>E</I> <SUB>H</SUB> decline occurs after 10h during the redox experiment. </LI> <LI> The second rapid <I>E</I> <SUB>H</SUB> change was found in soil treated with pine sawdust biomass. </LI> <LI> At low <I>E</I> <SUB>H</SUB>, biochar made at 550°C increased PLFA biomass compared to untreated soil. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>