A critical review on remediation, reuse, and resource recovery from acid mine drainage

Naidu, Gayathri,Ryu, Seongchul,Thiruvenkatachari, Ramesh,Choi, Youngkwon,Jeong, Sanghyun,Vigneswaran, Saravanamuthu Elsevier Applied Science Publishers 2019 Environmental pollution Vol.247 No.-

<P><B>Abstract</B></P> <P>Acid mine drainage (AMD) is a global environmental issue. Conventionally, a number of active and passive remediation approaches are applied to treat and manage AMD. Case studies on remediation approaches applied in actual mining sites such as lime neutralization, bioremediation, wetlands and permeable reactive barriers provide an outlook on actual long-term implications of AMD remediation. Hence, in spite of available remediation approaches, AMD treatment remains a challenge. The need for sustainable AMD treatment approaches has led to much focus on water reuse and resource recovery. This review underscores (i) characteristics and implication of AMD, (ii) remediation approaches in mining sites, (iii) alternative treatment technologies for water reuse, and (iv) resource recovery. Specifically, the role of membrane processes and alternative treatment technologies to produce water for reuse from AMD is highlighted. Although membrane processes are favorable for water reuse, they cannot achieve resource recovery, specifically selective valuable metal recovery. The approach of integrated membrane and conventional treatment processes are especially promising for attaining both water reuse and recovery of resources such as sulfuric acid, metals and rare earth elements. Overall, this review provides insights in establishing reuse and resource recovery as the holistic approach towards sustainable AMD treatment. Finally, integrated technologies that deserve in depth future exploration is highlighted.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Acid mine drainage (AMD) is a global environmental and economic challenge. </LI> <LI> Current AMD remediation applied at real sites and its limitations are highlighted. </LI> <LI> AMD challenges must be addressed through sustainable treatment approaches. </LI> <LI> Water reuse and valuable resource recovery potentially offset AMD treatment cost. </LI> <LI> Integrated processes using membranes are prospective approaches for AMD treatment. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Fouling study on vacuum-enhanced direct contact membrane distillation for seawater desalination

Naidu, Gayathri,Jeong, Sanghyun,Vigneswaran, Saravanamuthu,Jang, Eun-Kyung,Choi, Yong-Jun,Hwang, Tae-Mun Informa UK (Taylor Francis) 2016 Desalination and Water Treatment Vol.57 No.22

<P>Vacuum-enhanced direct contact membrane distillation (VE-DCMD) has been proposed to improve the DCMD system performance with better effective energy efficiency. However, the higher driving forces by the presence of vacuum pressure at permeate side of the VE-DCMD system could contribute to higher fouling development. In this study, thus, the biochemical fouling development of VE-DCMD with different vacuum pressures (700, 500, and 300mbar) for seawater desalination was investigated in comparison with DCMD (1,000mbar of pressure applied). VE-DCMD showed a significant increase in initial permeate flux while its flux decline was faster than DCMD. Low molecular weight (LMW) organics were found to be a dominant organic foulant on DCMD with thermally disaggregated humic substances (HS) to LMW HS-like organics. On the other hand, the presence of vacuum reduced the disaggregation HS to LMW HS-like organics. However, high driving force of VE-DCMD caused higher deposition of organic foulant including the LMW organics as well as HS. It also led to the higher LMW organic contents in permeate. Fluorescence excitation-emission matrix (F-EEM) analysis result showed that fulvic-like organic is a dominant HS foulant in VE-DCMD. Fouling development on membrane was observed using scanning electron microscope, contact angle, and confocal laser scanning microscope.</P>

Experiments and modeling of a vacuum membrane distillation for high saline water

Gayathri Naidu,최용준,정상현,황태문,Saravanamuthu Vigneswaran 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4

A modified design vacuum membrane distillation (VMD) system with high saline water was evaluated using different operating conditions (sustainable low feed temperature and flow velocity). At high salinity, a permeate flux of 13.9 to 15.8 L m-2 h-1 was achieved. Increasing the salinity from 1 to 3 M NaCl reduced the permeate flux by 18–20%. An increase in bulk feed temperature (310.2–319.2 K) significantly increased the permeate flux by 64%. The increase in flow velocity (1.1 to 2.2 m s-1) in turn increased the permeate flux by 14–20%. Model fluxes predicted was a good fit to experimental fluxes (R2 ≥ 0.94).

Valuable rubidium extraction from potassium reduced seawater brine

Naidu, Gayathri,Jeong, Sanghyun,Choi, Youngkwon,Song, Min Hyung,Oyunchuluun, Undram,Vigneswaran, Saravanamuthu Elsevier 2018 Journal of cleaner production Vol.174 No.-

<P><B>Abstract</B></P> <P>Extraction of rubidium (Rb) which is an economically valuable metal from seawater reverse osmosis (SWRO) brine is beneficial. However, potassium (K) in SWRO brine hinders Rb extraction. Natural clinoptilolite zeolite in powder form was able to selectively remove K from SWRO brine (Langmuir maximum sorption, Qmax (cal.) = 57.47 ± 0.09 mg/g). An integrated submerged membrane sorption reactor (SMSR) containing zeolite powder achieved 65% K removal from SWRO brine. Periodic replacement of zeolite in SMSR, coupled with membrane backwashing was effective in maintaining a high K removal efficiency and a stable transmembrane pressure. Less than 5% Rb losses occurred along with K sorption, establishing the high K selectivity by zeolite in SWRO brine. Utilization of K loaded zeolite as a slow release fertilizer would be beneficial for agriculture. In SWRO brine with reduced K contents, the Rb sorption efficiency of polymer encapsulated potassium copper hexacyanoferrate (KCuFC(PAN)) sorbent, increased significantly from 18% to 83%.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

해수담수화에서의 분리막을 이용한 자원회수

정상현,임승주,Gayathri Naidu,최영권,정다운,장암,Anthony G. Fane,Saravanamuthu Vigneswaran 한국막학회 2018 한국막학회 총회 및 학술발표회 Vol.2018 No.05

The ultimate goal of seawater reverse osmosis brine management is to achieve minimal liquid discharge while recovering valuable resources. The suitability of an integrated system of membrane distillation (MD) with sorption for the recovery of rubidium (Rb⁺) and simultaneous SWRO brine volume reduction has been evaluated for the first time. Polymer encapsulated potassium copper hexacyanoferrate (KCuFC(PAN)) sorbent exhibited a good selectivity for Rb⁺ sorption. The integrated MD-KCuFC (PAN) system with periodic membrane cleaning, enabled 65% water recovery. A stable MD permeate flux was achieved with good quality permeate. KCuFC (PAN) showed a high regeneration and reuse capacity. Ammonium chloride air stripping followed by resorcinol formaldehyde resin filtration enabled to recover Rb⁺ from the desorbed solution.

Fractional-submerged membrane distillation crystallizer (F-SMDC) for treatment of high salinity solution

Choi, Youngkwon,Naidu, Gayathri,Jeong, Sanghyun,Lee, Sangho,Vigneswaran, Saravanamuthu Elsevier 2018 Desalination Vol.440 No.-

<P><B>Abstract</B></P> <P>Membrane distillation with crystallization (MDC) is an attractive process for high saline seawater reverse osmosis (SWRO) brine treatment. MDC produces additional fresh water while simultaneously recovering valuable resources. This study developed a novel approach of fractional-submerged MDC (F-SMDC) process, in which MD and crystallizer are integrated in a feed tank with a submerged membrane. F-SMDC principle is based on the presence of temperature/concentration gradient (TG/CG) in the feed reactor. The operational conditions at the top portion of the feed reactor (higher temperature and lower feed concentration) was well suited for MD operation, while the bottom portion of the reactor (lower temperature and higher concentration) was favourable for crystal growth. F-SMDC performance with direct contact MD to treat brine and produce sodium sulfate (Na<SUB>2</SUB>SO<SUB>4</SUB>) crystals using TG/CG showed positive results. The TG/CG approach in F-SMDC enabled to achieve higher water recovery for brine treatment with a volume concentration factor (VCF) of over 3.5 compared to VCF of 2.9 with a conventional S-MDC set-up. Further, the high feed concentration and low temperature at the reactor bottom in F-SMDC enabled the formation of Na<SUB>2</SUB>SO<SUB>4</SUB> crystals with narrow crystal size distribution.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fractional-submerged MDC (F-SMDC) showed promising potential for brine treatment. </LI> <LI> Concentration/temperature gradients (CG/TG) in F-SMDC reactor were beneficial. </LI> <LI> High TG/low CG at reactor top enabled to reduce the scaling on MD membrane. </LI> <LI> Low TG/high CG at reactor bottom was favourable for sodium sulfate crystallization. </LI> <LI> Stable CG/TG in F-SMDC required periodic crystal extraction from the reactor. </LI> </UL> </P>

Acid mine drainage treatment by integrated submerged membrane distillation–sorption system

Ryu, Seongchul,Naidu, Gayathri,Hasan Johir, Md Abu,Choi, Youngkwon,Jeong, Sanghyun,Vigneswaran, Saravanamuthu Elsevier 2019 CHEMOSPHERE - Vol.218 No.-

<P><B>Abstract</B></P> <P>Acid mine drainage (AMD), an acidic effluent characterized by high concentrations of sulfate and heavy metals, is an environmental and economic concern. The performance of an integrated submerged direct contact membrane distillation (DCMD) – zeolite sorption system for AMD treatment was evaluated. The results showed that modified (heat treated) zeolite achieved 26–30% higher removal of heavy metals compared to natural untreated zeolite. Heavy metal sorption by heat treated zeolite followed the order of Fe > Al > Zn > Cu > Ni and the data fitted well to Langmuir and pseudo second order kinetics model. Slight pH adjustment from 2 to 4 significantly increased Fe and Al removal rate (close to 100%) due to a combination of sorption and partial precipitation. An integrated system of submerged DCMD with zeolite for AMD treatment enabled to achieve 50% water recovery in 30 h. The integrated system provided a favourable condition for zeolite to be used in powder form with full contact time. Likewise, heavy metal removal from AMD by zeolite, specifically Fe and Al, mitigated membrane fouling on the surface of the hollow fiber submerged membrane. The integrated system produced high quality fresh water while concentrating sulfuric acid and valuable heavy metals (Cu, Zn and Ni).</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Performance evaluation of carbon nanotube enhanced membranes for SWRO pretreatment application

이지은,정상현,Gayathri Naidu,Yun Ye,Vicki Chen,Zongwen Liu,Saravanamuthu Vigneswaran 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.38 No.-

Multi-wall carbon nanotube (MWCNT) membrane was tested for SWRO pretreatment. The MWCNTmembrane itself showed a superior permeate flux (321.3 LMH/bar), which was 4-times aspolyethersulfone ultrafiltration (PES-UF) membrane. Reduction of dissolved organic matter improvedto 66% with fewer amounts of powder activated carbon (PAC) (0.5 g/L) in MWCNT membrane filtrationmaintaining a high permeate flux of 600 LMH/bar. It was due to the increased porosity (84.5%) andhydrophilicity (52.98) by incorporating MWCNT/polyaniline into PES membrane. Ionic strength affectedorganic removal in seawater filtration by altering electrostatic interaction between organic matter andsurface charge of the positively charged MWCNT membrane.