Aging effects on chemical transformation and metal(loid) removal by entrapped nanoscale zero-valent iron for hydraulic fracturing wastewater treatment

Sun, Yuqing,Lei, Cheng,Khan, Eakalak,Chen, Season S.,Tsang, Daniel C.W.,Ok, Yong Sik,Lin, Daohui,Feng, Yujie,Li, Xiang-dong Elsevier 2018 Science of the Total Environment Vol.615 No.-

<P><B>Abstract</B></P> <P>In this study, alginate and polyvinyl alcohol (PVA)-alginate entrapped nanoscale zero-valent iron (nZVI) was tested for structural evolution, chemical transformation, and metals/metalloids removal (Cu(II), Cr(VI), Zn(II), and As(V)) after 1–2month passivation in model saline wastewaters from hydraulic fracturing. X-ray diffraction analysis confirmed successful prevention of Fe<SUP>0</SUP> corrosion by polymeric entrapment. Increasing ionic strength (<I>I</I>) from 0 to 4.10M (deionized water to Day-90 fracturing wastewater (FWW)) with prolonged aging time induced chemical instability of alginate due to dissociation of carboxyl groups and competition for hydrogen bonding with nZVI, which caused high Na (7.17%) and total organic carbon (24.6%) dissolution from PVA-alginate entrapped nZVI after 2-month immersion in Day-90 FWW. Compared to freshly-made beads, 2-month aging of PVA-alginate entrapped nZVI in Day-90 FWW promoted Cu(II) and Cr(VI) uptake in terms of the highest removal efficiency (84.2% and 70.8%), pseudo-second-order surface area-normalized rate coefficient <I>k</I> <SUB> <I>sa</I> </SUB> (2.09×10<SUP>−1</SUP> Lm<SUP>−2</SUP> h<SUP>−1</SUP> and 1.84×10<SUP>−1</SUP> Lm<SUP>−2</SUP> h<SUP>−1</SUP>), and Fe dissolution after 8-h reaction (13.9% and 8.45%). However, the same conditions inhibited Zn(II) and As(V) sequestration in terms of the lowest removal efficiency (31.2% and 39.8%) by PVA-alginate nZVI and <I>k</I> <SUB> <I>sa</I> </SUB> (4.74×10<SUP>−2</SUP> Lm<SUP>−2</SUP> h<SUP>−1</SUP> and 6.15×10<SUP>−2</SUP> Lm<SUP>−2</SUP> h<SUP>−1</SUP>) by alginate nZVI. The X-ray spectroscopic analysis and chemical speciation modelling demonstrated that the difference in metals/metalloids removal by entrapped nZVI after aging was attributed to distinctive removal mechanisms: (i) enhanced Cu(II) and Cr(VI) removal by nZVI reduction with accelerated electron transfer after pronounced dissolution of non-conductive polymeric immobilization matrix; (ii) suppressed Zn(II) and As(V) removal by nZVI adsorption due to restrained mass transfer after blockage of surface-active micropores. Entrapped nZVI was chemically fragile and should be properly stored and regularly replaced for good performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> nZVI entrapment successfully prevented Fe<SUP>0</SUP> corrosion in fracturing wastewaters. </LI> <LI> Entrapped nZVI was chemically fragile due to dissolution of Na and TOC. </LI> <LI> nZVI passivation promoted Cu(II) and Cr(VI) but inhibited Zn(II) and As(V) removal. </LI> <LI> Effects of nZVI aging on removal efficiency depended on interaction mechanisms. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Removal of chlorinated organic solvents from hydraulic fracturing wastewater by bare and entrapped nanoscale zero-valent iron

Lei, Cheng,Sun, Yuqing,Khan, Eakalak,Chen, Season S.,Tsang, Daniel C.W.,Graham, Nigel J.D.,Ok, Yong Sik,Yang, Xin,Lin, Daohui,Feng, Yujie,Li, Xiang-Dong Elsevier 2018 CHEMOSPHERE - Vol.196 No.-

<P><B>Abstract</B></P> <P>With the increasing application of hydraulic fracturing, it is urgent to develop an effective and economically feasible method to treat the large volumes of fracturing wastewater. In this study, bare and entrapped nanoscale zero-valent iron (nZVI) were introduced for the removal of carbon tetrachloride (CT) and 1,1,2-trichloroethane (TCA) in model high-salinity fracturing wastewater. With increasing ionic strength (<I>I</I>) from Day-1 (<I>I</I> = 0.35 M) to Day-90 (<I>I</I> = 4.10 M) wastewaters, bare nZVI presented significantly lower removal efficiency of CT (from 53.5% to 38.7%) and 1,1,2-TCA (from 71.1% to 21.7%) and underwent more serious Fe dissolution from 1.31 ± 1.19% in Day-1 to 5.79 ± 0.32% in Day-90 wastewater. Particle aggregation induced by high ionic strength was primarily responsible for the lowered performance of nZVI due to less available reactive sites on nZVI surface. The immobilization of nZVI in alginate with/without polyvinyl alcohol provided resistance to particle aggregation and contributed to the superior performance of entrapped nZVI in Day-90 wastewater for 1,1,2-TCA removal (62.6–72.3%), which also mitigated Fe dissolution (4.00–4.69%). Both adsorption (by polymer matrix) and reduction (by immobilized nZVI) were involved in the 1,1,2-TCA removal by entrapped nZVI. However, after 1-month immersion in synthetic fracturing wastewater, a marked drop in the reactivity of entrapped nZVI for 1,1,2-TCA removal from Day-90 wastewater was observed with significant release of Na and total organic carbon. In summary, bare nZVI was sensitive to the nature of the fracturing wastewater, while the use of environmentally benign entrapped nZVI was more promising for wastewater treatment.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Increasing ionic strength decreased nZVI reactivity and increased Fe dissolution. </LI> <LI> Entrapping nZVI in polymer matrix improved reactivity and limited Fe dissolution. </LI> <LI> Entrapped nZVI removed model chlorinated organic via both adsorption and reduction. </LI> <LI> Aging process was mitigated by polymer matrix but still inhibited nZVI reactivity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Nanoscale zero-valent iron for metal/metalloid removal from model hydraulic fracturing wastewater

Sun, Yuqing,Lei, Cheng,Khan, Eakalak,Chen, Season S.,Tsang, Daniel C.W.,Ok, Yong Sik,Lin, Daohui,Feng, Yujie,Li, Xiang-dong Elsevier 2017 CHEMOSPHERE - Vol.176 No.-

<P><B>Abstract</B></P> <P>Nanoscale zero-valent iron (nZVI) was tested for the removal of Cu(II), Zn(II), Cr(VI), and As(V) in model saline wastewaters from hydraulic fracturing. Increasing ionic strength (<I>I</I>) from 0.35 to 4.10 M (Day-1 to Day-90 wastewaters) increased Cu(II) removal (25.4–80.0%), inhibited Zn(II) removal (58.7–42.9%), slightly increased and then reduced Cr(VI) removal (65.7–44.1%), and almost unaffected As(V) removal (66.7–75.1%) by 8-h reaction with nZVI at 1–2 g L<SUP>−1</SUP>. The removal kinetics conformed to pseudo-second-order model, and increasing <I>I</I> decreased the surface area-normalized rate coefficient (<I>k</I> <SUB> <I>sa</I> </SUB>) of Cu(II) and Cr(VI), probably because agglomeration of nZVI in saline wastewaters restricted diffusion of metal(loid)s to active surface sites. Increasing <I>I</I> induced severe Fe dissolution from 0.37 to 0.77% in DIW to 4.87–13.0% in Day-90 wastewater; and Fe dissolution showed a significant positive correlation with Cu(II) removal. With surface stabilization by alginate and polyvinyl alcohol, the performance of entrapped nZVI in Day-90 wastewater was improved for Zn(II) and Cr(VI), and Fe dissolution was restrained (3.20–7.36%). The X-ray spectroscopic analysis and chemical speciation modelling demonstrated that the difference in removal trends from Day-1 to Day-90 wastewaters was attributed to: (i) distinctive removal mechanisms of Cu(II) and Cr(VI) (adsorption, (co-)precipitation, and reduction), compared to Zn(II) (adsorption) and As(V) (bidentate inner-sphere complexation); and (ii) changes in solution speciation (e.g., from Zn<SUP>2+</SUP> to ZnCl<SUB>3</SUB> <SUP>−</SUP> and ZnCl<SUB>4</SUB> <SUP>2−</SUP>; from CrO<SUB>4</SUB> <SUP>2−</SUP> to CaCrO<SUB>4</SUB> complex). Bare nZVI was susceptible to variations in wastewater chemistry while entrapped nZVI was more stable and environmentally benign, which could be used to remove metals/metalloids before subsequent treatment for reuse/disposal.</P> <P><B>Highlights</B></P> <P> <UL> <LI> nZVI could remove Cu(II), Zn(II), Cr(VI), and As(V) from fracturing wastewaters. </LI> <LI> High salinity enhanced Fe dissolution and reduced removal rates except Cu(II). </LI> <LI> nZVI entrapment mitigated Fe dissolution and improved metal(loid) removal. </LI> <LI> Removal efficiency varied with interaction mechanisms and solution speciation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Development of Electrokinetic Remediation System for Mercury Contaminated Marine Sediment

Chotikoon Bunditboondee,Jenyuk Lohwacharin,Eakalak Khan,Kritapas Laohhasurayotin 대한환경공학회 2019 대한환경공학회 학술발표논문집 Vol.2019 No.-

1,4-Dioxane의 초음파 처리시 반응 온도와 부피의 영향

손현석(Hyun Seok Son),최석봉(Seok Bong Choi),Khan Eakalak,조경덕(Kyung Duk Zoh) 大韓環境工學會 2005 대한환경공학회지 Vol.27 No.10

초음파를 이용한 1,4-Dioxane의 처리에서 OH 라디칼의 기여와 산화제 첨가의 효과

손현석(Hyun Seok Son),최석봉(Seok Bong Choi),Eakalak Khan,조경덕(Kyung Duk Zoh) 大韓環境工學會 2005 대한환경공학회지 Vol.27 No.6

Sustainability likelihood of remediation options for metal-contaminated soil/sediment

Chen, Season S.,Taylor, Jessica S.,Baek, Kitae,Khan, Eakalak,Tsang, Daniel C.W.,Ok, Yong Sik Elsevier 2017 CHEMOSPHERE - Vol.174 No.-

<P><B>Abstract</B></P> <P>Multi-criteria analysis and detailed impact analysis were carried out to assess the sustainability of four remedial alternatives for metal-contaminated soil/sediment at former timber treatment sites and harbour sediment with different scales. The sustainability was evaluated in the aspects of human health and safety, environment, stakeholder concern, and land use, under four different scenarios with varying weighting factors. The Monte Carlo simulation was performed to reveal the likelihood of accomplishing sustainable remediation with different treatment options at different sites. The results showed that <I>in-situ</I> remedial technologies were more sustainable than <I>ex-situ</I> ones, where <I>in-situ</I> containment demonstrated both the most sustainable result and the highest probability to achieve sustainability amongst the four remedial alternatives in this study, reflecting the lesser extent of off-site and on-site impacts. Concerns associated with <I>ex-situ</I> options were adverse impacts tied to all four aspects and caused by excavation, extraction, and off-site disposal. The results of this study suggested the importance of considering the uncertainties resulting from the remedial options (i.e., stochastic analysis) in addition to the overall sustainability scores (i.e., deterministic analysis). The developed framework and model simulation could serve as an assessment for the sustainability likelihood of remedial options to ensure sustainable remediation of contaminated sites.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Remediation sustainability depends on site conditions and stakeholder preferences. </LI> <LI> Monte Carlo simulation reveals the uncertainty in sustainability scores. </LI> <LI> <I>In-situ</I> remediation generates the highest sustainability probability. </LI> <LI> Both deterministic and stochastic assessments assist decision-making process. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

광반응을 이용한 Triclosan 분해에서의 UV 광세기와 파장의 효과

손현석(Hyun Seok Son),최석봉(Seok Bong Choi),Eakalak Khan,조경덕(Kyung Duk Zoh) 大韓環境工學會 2005 대한환경공학회지 Vol.27 No.9