Removal of humic acid from water using adsorption coupled with electrochemical regeneration

Hafiz Muhammad Anwaar Asghar,Syed Nadir Hussain,Edward Pelham Lindfield Roberts,Nigel Willis Brown 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.7

A novel and economic waste water treatment technology comprised of adsorption coupled with electrochemical regeneration was introduced at the University of Manchester in 2006. An electrically conducting adsorbent material called NyexTM 1000 (Graphite intercalation based material) was developed for the said purpose. This adsorbent material delivered significantly lower adsorption capacity for the removal of a number of organic pollutants. With the aim to expand the scope of newly developed adsorbent material called NyexTM 2000, we studied the adsorption of humic acid followed by electrochemical regeneration. NyexTM 2000 is a highly electrically conducting material with an adsorption capacity almost twice that of NyexTM 1000 (intercalation based graphite compound) for humic acid. The adsorption of humic acid onto both NyexTM adsorbents was found to be fast enough keeping almost the same kinetics with approximately 50% of the adsorption capacity being achieved within the first twenty minutes. The parameters affecting the regeneration efficiency, including the treatment time, charge passed and current density, were investigated. The regeneration efficiency at around 100% for NyexTM 1000 & 2000 adsorbents saturated with humic acid was obtained using the charge passed of 8 and 22 Cg−1 at a current density of 7mA cm−2 during a treatment time of 30minutes,respectively.

Synthesis of electrically conducting composite adsorbents for wastewater treatment using adsorption & electrochemical regeneration

H.M.A. Asghar,S.N. Hussain,N.W. Brown,E.P.L. Roberts 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.3

Electrically conducting adsorbent materials called NyexTM 1000 & 2000 have already been reported withcomparatively low adsorption capacity for various organic, biologically non-degradable and toxiccompounds. Two composite adsorbents called CA1 & CA2 were synthesized using synthetic graphite-carbon black and expanded graphite-carbon black respectively. The aim of developing the newadsorbents was to increase the adsorption capacity along with good electrical properties. The developedadsorbents were characterized using N2 adsorption for specific surface area, Boehm surface titration forsurface chemistry, bed electrical conductivity, laser size analyzer for average particle size, and scanningelectron microscope (SEM) for particle morphology and shape. Then both the composite adsorbents weretested for the adsorption of acid violet 17 followed by an electrochemical regeneration. The adsorptionstudy revealed that both the adsorbents had almost similar kinetic behavior with a significant increase inadsorption capacity for acid violet 17 (300 & 26 mg g-1 respectively) when compared with theadsorption capacity of previously developed electrically conducting materials called NyexTM 1000 &2000 (3.5 and 9 mg g-1 respectively). The composite adsorbent CA2 was successfully electrochemicallyregenerated by passing an electric charge of 138 C g-1 at a current density of 14 mA cm-2 for a treatmenttime of 60 min, whereas, the composite adsorbent CA1 could not be regenerated successfully. Theregeneration efficiencies of CA2 were obtained at around 120% during five adsorption–regenerationcycles. The amount of actual charge passed of 138 C g-1 for achieving 100% regeneration efficiency wasfound to be similar with stoichiometrically calculated amount of charge. The amount of electrical energyrequired to oxidize each mg of adsorbed acid violet onto CA2 (24 J mg-1) was found to be significantlylower to that of NyexTM 1000 & 2000 adsorbents (52 J mg-1 & 32 J mg-1 respectively).

Chlorinated breakdown products formed during oxidation of adsorbed phenol by electrochemical regeneration of a graphite intercalation compound

S.N. Hussain,H.M.A. Asghar,H. Sattar,N.W. Brown,E.P.L. Roberts 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.30 No.-

The process of adsorption using graphite intercalation compound (GIC) adsorbent with electrochemicalregeneration has been investigated for the removal and oxidation of phenol in wastewater. The presentstudy deals with the formation of chlorinated breakdown products released in treated water duringelectrochemical regeneration of GIC adsorbents. The main chlorinated breakdown products observedwere 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol with lower concentrations of 2,4-dichlorophenol than 2-chlorophenol and 4-chlorophenol. Experiments performed at low current density( 10 mA cm 2), low initial phenol concentration (10 mg L 1), and use of a chloride free catholyteminimised the concentration of chlorinated breakdown products. In addition, only a few mg L 1 of 2,4-dichlorphenol and 3,5-dichlorophenol were observed after five adsorption cycles operated in batchrecycle mode for an initial phenol concentration of 50 mg L 1. The formation of chlorinated breakdownproducts was found largely to be associated with the oxidation of phenol from solution as opposed to theadsorbed phenol. These results have important implications in reducing the formation of chlorinatedbreakdown products during wastewater treatment by adsorption and electrochemical regeneration.

Pre-treatment of adsorbents for waste water treatment using adsorption coupled-with electrochemical regeneration

H.M.A. Asghar,S.N. Hussain,E.P.L. Roberts,A.K. Campen,N.W. Brown 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.5

With the aim to address waste water treatment problems, a novel and economic water treatment technology was introduced at the University of Manchester. It comprised of a unique combination of adsorption and electrochemical regeneration in a single unit. This process successfully eliminated a number of organic pollutants by using an electrically conducting adsorbent material called NyexTM which was a modified form of synthetic graphite. To expand the scope of other graphite types in waste water treatment applications, natural vein and recycled vein graphite materials were selected for electrochemical surface treatment (pre-treatment) in order to evaluate their adsorptive and electrical properties. New graphite based adsorbents were developed and characterized using a laser diffraction particle size analyser,BET surface area, SEM analysis, X-ray (EDS) elemental analysis, X-ray powder diffraction, Boehm surface titration, Zeta potential electrical bed conductivity and bulk density measurements. Boehm surface titration and EDS (X-ray) elemental analysis showed a significant increase in oxygen containing surface functional groups. Although, no significant improvement in bed electrical conductivity was found to occur after electrochemical surface treatment, however, natural vein and recycled vein graphite materials presented highest bed electrical conductivity amongst competing graphite materials. Aqueous solution of acid violet 17 as a standard pollutant was used to evaluate the comparative performance of these adsorbents. The investigations revealed that electrochemical surface treatment contributed to an increase in the adsorption capacity by a factor of two only for natural vein graphite. Un-treated recycled vein graphite adsorbent delivered the same adsorptive capacity (3.0 mg g-1) to that of electrochemically treated natural vein graphite. The electrochemical regeneration efficiency at around 100% was obtained using a treatment time of 60 and 30 min, current density of 14 mA cm-2, charge passed of 36 and 18 C g-1 for synthetic graphite, natural and recycled vein graphite materials respectively. Relatively a small consumption of electrical energy, 24 J g-1 for regenerating natural vein graphite adsorbent versus 36 J g-1 for synthetic graphite adsorbent, was found to be required for destruction/oxidation of adsorbed acid violet 17. Multiple adsorption/regeneration cycles presented no loss in adsorptive capacity over 5adsorption/regeneration cycles. The use of natural and recycled vein graphite adsorbents offered some advantages over graphite intercalation based adsorbents with reduced electrical energy consumption during regeneration and simpler separation of particulate adsorbent.

Electrochemically synthesized GIC-based adsorbents for water treatment through adsorption and electrochemical regeneration

H.M.A. Asghar,S.N. Hussain,H. Sattar,N.W. Brown,E.P.L. Roberts 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4

The flake GIC material delivered a small adsorptive capacity for a number of organic pollutants, however, underwent quick adsorption and electrochemical regeneration in minutes. In this study, binary and ternary GIC-based adsorbents were prepared using electrochemical intercalation of Chinese large flake graphite (CLFG) and Madagascan medium flake graphite (MMFG) materials. In this context GICbisulphate, GIC-nitrate, GIC-bisulphate-acetate, GIC nitrate-bisulphate, and GIC-nitrate-acetate were developed and characterized in order to evaluate their adsorptive and electrical properties. The adsorption behaviour was studied using an organic dye, acid violet 17, as a model dissolved organic pollutant. The treatment time and acid concentration for electrochemical intercalation were optimized in order to maximize the adsorptive capacity of the GIC based adsorbents. GIC-bisulphate delivered double adsorptive capacity after electrochemical intercalation, whereas, GIC nitrate diminished the adsorptive capacity to one half that of GIC bisulphate. However, no significant effect of ternary intercalated compounds was observed in terms of improved adsorption capacity or electrical conductivity.

Regeneration of the nicotinamide cofactor using a mediator-free electrochemical method with a tin oxide electrode

Kim, Y.H.,Yoo, Y.J. IPC Science and Technology Press ; Elsevier Scienc 2009 Enzyme and microbial technology Vol.44 No.3

Tin (IV) oxide was made using an anodization and annealing method and was used as a working electrode in an electrochemical cofactor regeneration reaction. This material was formed with a large surface area, and by changing the preparation conditions, it was possible to control the morphology. Tin oxide has redox properties similar to those of frequently used mediators required for electron transfer between cofactors and an electrode. Therefore, by using tin oxide as a novel electrode, mediator-free electrochemical cofactor regeneration may be possible. Oxidation and reduction of the nicotinamide cofactors, NAD(P)H and NAD(P)<SUP>+</SUP>, were carried out under various reaction conditions. The results showed a high efficiency for oxidizing NADH over a broad range of pH and temperatures. The oxidation tendency of NADPH was also observed, and it demonstrated a similar reaction tendency as NADH. When using a tin oxide electrode, NAD<SUP>+</SUP> was readily reduced to NADH, though the efficiency of this reaction was lower than for NADH oxidation. Oxidation of 2-propanol to acetone was used as a model system using alcohol dehydrogenase and the cofactor regeneration system suggested in this study. The electroenzymatic reaction showed efficient regeneration of NADP<SUP>+</SUP> without a mediator.

Electrochemical Capacitance of Activated Carbons Regenerated using Thermal and Chemical Activation

Park, Jung Eun,Lee, Gi Bbum,Hwang, Sang Youp The Korean Electrochemical Society 2021 Journal of electrochemical science and technology Vol.12 No.3

Spent activated carbons (SACs) collected from a water treatment plant were regenerated and then adopted as electrochemical material in capacitors. The SACs used in this study were regenerated via two steps, namely thermal and chemical activation. However, during the activation process, the adsorbates were converted into ashes, which caused pore blockage and decreased specific surface area. The regenerated SACs were washed with acid solutions with different levels of acidity (strong: HCl, mild: H₃PO₄, and weak: H₂O₂) to remove the ashes. The regenerated SACs washed with HCl exhibited the highest specific surface area, although their capacitance was not the highest. Conversely, the specific surface area of regenerated SACs washed using H₃PO₄ was slightly lower than that of HCl, but exhibited higher capacitance and electrochemical stability. Although the strong acid removed the generated ashes in the pores efficiently, it could adversely affect their structural stability, which would lead to lower capacitance.

Comparative adsorption–regeneration performance for newly developed carbonaceous adsorbent

H.M.A. Asghar,S.N. Hussain,N.W. Brown,E.P.L. Roberts 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.69 No.-

A proprietary adsorbent material called Nyex 1000 was developed by the Arvia Technology Ltd. (UK based waste water treatment company). Nyex 1000 was being employed for a number of commercial applications dealing with the removal of organic contaminants from industrial effluents. This adsorbent material had small adsorptive capacity. With the aim to address small adsorptive capacity, a new graphite based adsorbent material was developed. The particle design was accomplished through successive chemical, thermal and mechanical treatments of raw graphite material (natural large flake graphite, to be called here as NLFG). The chemical treatment of the NLFG was carried out through electrochemical intercalation using dilute (50%) sulfuric acid in an electrochemical cell. Chemically treated NLFG then went through thermal treatment at 850 °C and followed by mechanical treatments consisting of compression (4536 kgf cm−2) and chopping at 18,000 rpm for 30 s. The developed adsorbent material, (exfoliated compacted graphite, to be called here as ECG) and NLFG were characterized using state of the art techniques including SEM, BET surface area, XRD, Zeta potential, Boehm surface titration, bed electrical conductivity and laser size analysis. The characterization results showed significant increase in internal specific surface area from 1 to 17 m2 g−1. It was attributed to the development of partially porous particle surface verified by SEM results. The XRD, Boehm surface titration, Zeta potential results endorsed the associated chemical and physical changes appeared in the composition of the NLFG as a result of chemical, thermal and mechanical treatments. Adsorption-regeneration studies were conducted using developed ECG and existing Nyex 1000 materials. The pollutants used for adsorption–regeneration studies were acid violet 17, phenol, humic acid, ethane thiol and methyl propane thiol dissolved in aqueous solution. The results were compared and it was found that ECG showed significantly improved adsorption capacity with many folds. Both adsorbent materials, ECG and Nyex 1000 delivered 100% electrochemical regeneration efficiencies.

INVESTIGATION OF DYE-REGENERATION KINETICS AT DYE-SENSITIZED p-TYPE CuCrO 2 FILM/ELECTROLYTES INTERFACE WITH SCANNING ELECTROCHEMICAL MICROSCOPY

GETACHEW ALEMU,MINGKUI WANG,BINGYAN ZHANG,JUNPENG LI,XIAOBAO XU,JIN CUI,YAN SHEN 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2014 NANO Vol.9 No.5

The power conversion e±ciency of p-type dye-sensitized solar cells (DSSC) is determined by thekinetics of hole injection and dye-regeneration reaction at the dye/electrolyte interface. In thiswork, the photochemical regeneration kinetics of dye adsorbed on CuCrO 2 mesoporous ¯lm wasinvestigated by using scanning electrochemical microscopy with feedback mode. Organic P1 andC343 sensitizers in combination with iodide-based and thiolate-based electrolytes were selected tounderstand the e®ect of sensitizers and redox shuttles on dye-regeneration process. A fast re-generation kinetic rate constant was con¯rmed in thiolate-based sample compared with iodide-based electrolyte, indicating that the organic redox shuttle was an e±cient mediator to optimizethe performance of p-type DSSC.

Disinfection performance of adsorption using graphite adsorbent coupled with electrochemical regeneration for various microorganisms present in water

S.N. Hussain,A.P. Trzcinski,H.M.A. Asghar,H. Sattar,N.W. Brown,E.P.L. Roberts 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.44 No.-

The disinfection performance of the process of adsorption using a graphitic material combined withelectrochemical regeneration for a range of microorganisms including bacteria, fungi, yeast and protozoain a laboratory scale sequential batch reactor is demonstrated. The bacterial species studied werePseudomonas aeruginosa,Staphylococcus aureus and Legionella pneumophila. A 3.0 log10 reduction in theconcentration of P. aeruginosa cells was achieved with the adsorbent that was regenerated at 30 mA cm 2with 100% regeneration on each adsorption cycle. The process was quite effective in removing S. aureuspresent in water with a significantly higher reduction in the number of cells (ca. 9-log10 reduction) atrelatively low current density (10 mA cm 2). Similarly, L. pneumophila were removed from water with aca. 7.5-log10 reduction in the number of bacterial cells. The SEM images confirmed the adsorption of L. pneumophila onto the adsorbent and its electrochemical regeneration at 20 mA cm 2 that is considered arefractory pathogen against chlorination. The process was also found to be suitable for disinfecting fungalspores, Aspergillus awamori and yeasts including Saccharomyces cerevisiae and Rhodosporidium turoloidesHowever, the removal of Cryptosporidium parvum from water was not demonstrated successfully. Thepreliminary results suggest that using a chloride free environment and a relatively high current densitycould be useful in disinfecting C. parvum.