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Accumulation of chromium (VI) from aqueous solutions using water lilies (Nymphaea spontanea)

Choo TP, Lee CK, Low KS, Hishamuddin O

Chemosphere, 2006 Feb;62(6):961-7.
PMID: 16081131

This study describes an investigation using tropical water lilies (Nymphaea spontanea) to remove hexavalent chromium from aqueous solutions and electroplating waste. The results show that water lilies are capable of accumulating substantial amount of Cr(VI), up to 2.119 mg g(-1) from a 10 mg l(-1) solution. The roots of the plant accumulated the highest amount of Cr(VI) followed by leaves and petioles, indicating that roots play an important role in the bioremediation process. The maturity of the plant exerts a great effect on the removal and accumulation of Cr(VI). Plants of 9 weeks old accumulated the most Cr(VI) followed by those of 6 and 3 weeks old. The results also show that removal of Cr(VI) by water lilies is more efficient when the metal is present singly than in the presence of Cu(II) or in waste solution. This may be largely associated with more pronounced phytotoxicity effect on the biochemical changes in the plants and saturation of binding sites. Significant toxicity effect on the plant was evident as shown in the reduction of chlorophyll, protein and sugar contents in plants exposed to Cr(VI) in this investigation.

Matched MeSH terms: Chromium/isolation & purification; Chromium/metabolism*; Chromium/toxicity
Fulltext Polymer Ligands Derived from Jute Fiber for Heavy Metal Removal from Electroplating Wastewater

Rahman ML, Fui CJ, Ting TX, Sarjadi MS, Arshad SE, Musta B

Polymers (Basel), 2020 Oct 29;12(11).
PMID: 33137923 DOI: 10.3390/polym12112521

Industrial operations, domestic and agricultural activities worldwide have had major problems with various contaminants caused by environmental pollution. Heavy metal pollution in wastewater also a prominent issue; therefore, a well built and economical treatment technology is demanded for pollution-free wastewater. The present work emphasized pure cellulose extracted from jute fiber and further modification was performed by a free radical grafting reaction, which resulted in poly(methyl acrylate) (PMA)-grafted cellulose and poly(acrylonitrile)-grafted cellulose. Subsequently, poly(hydroxamic acid) and poly(amidoxime) ligands were prepared from the PMA-grafted cellulose and PAN-grafted cellulose, respectively. An adsorption study was performed using the desired ligands with heavy metals such as copper, cobalt, chromium and nickel ions. The binding capacity (qe) with copper ions for poly(hydroxamic acid) is 352 mg g-1 whereas qe for poly(amidoxime) ligand it was exhibited as 310 mg g-1. Other metal ions (chromium, cobalt and nickel) show significance binding properties at pH 6. The Langmuir and Freundlich isotherm study was also performed. The Freundlich isotherm model showed good correlation coefficients for all metal ions, indicating that multiple-layers adsorption was occurred by the polymer ligands. The reusability was evaluated and the adsorbents can be reused for 7 cycles without significant loss of removal performance. Both ligands showed outstanding metals removal capacity from the industrial wastewater as such 98% of copper can be removed from electroplating wastewater and other metals (cobalt, chromium, nickel and lead) can also be removed up to 90%.

Matched MeSH terms: Chromium
Enhanced visible-light driven multi-photoredox Cr(VI) and p-cresol by Si and Zr interplay in fibrous silica-zirconia

Aziz FFA, Jalil AA, Hassan NS, Hitam CNC, Rahman AFA, Fauzi AA

J Hazard Mater, 2021 Jan 05;401:123277.
PMID: 33113710 DOI: 10.1016/j.jhazmat.2020.123277

Multiple contaminants including heavy metals and phenolic compounds are normally co-exist in wastewater, which caused the treatment process is rather complicated. Herein, the synergistic photoredox of Cr(VI) and p-cresol (pC) by innovative fibrous silica zirconia (FSZr) photocatalyst was reported. The high surface area of FSZr comprised of microspheres with a bicontinuous concentric lamella structure morphology consisted of silica, while its core consisted of ZrO2 structure. The rearrangement of FSZr framework increased the crystallinity, formed Si-O-Zr bonds and narrowed the band gap of ZrO2 for enhanced of photoredox of Cr(VI) and pC. Compared to the reaction, the photoredox efficiency of FSZr for removing Cr(VI) and pC in simultaneous system was found to be 96 % and 59 %, respectively which are higher than that in its single system owing to the efficient electron-hole charge separation. Phenolic compound with high degree of electron donating group gave beneficial effect to photoreduction of Cr(VI). Consequently, a proposed mechanism involving multi-photoredox pathway were proposed based on photoredox reaction and scavengers studies. FSZr sustained the simultaneous photoredox activities after five runs demonstrating its possibility to be use in the wastewater treatment of various pollutants.

Matched MeSH terms: Chromium
Fulltext Bioadsorption of multiple heavy metal ions by rhizophora apiculate sp. and elaesis guineensis sp.

Nicodemus Ujih, M.B., Mohammad Isa Mohamadin, Millaa Armila Asli, Bebe Norlita Mohamed

Scientific Research Journal, 2017;14(1):15-27.
MyJurnal

Heavy metal ions contamination has become more serious which is caused
by the releasing of toxic waterfrom industrial area and landfill that are very
harmful to all living organism especially human and can even cause death
if contaminated in small amount of heavy metal concentration. Currently,
peoples are using classic method namely electrochemical treatment,
chemical oxidation/reduction, chemical precipitation and reverse osmosis
to eliminate the metal ions from toxic water. Unfortunately, these methods
are costly and not environmentally friendly as compared to bioadsorption
method, where agricultural waste is used as biosorbent to remove heavy
metals. Two types of agricultural waste used in this research namely oil
palm mesocarp fiber (Elaesis guineensis sp.) (OPMF) and mangrove bark
(Rhizophora apiculate sp.) (MB) biomass. Through chemical treatment,
the removal efficiency was found to improve. The removal efficiency is
examined based on four specification namely dosage, of biosorbent to
adsorb fourtypes of metalsion explicitly nickel, lead, copper, and chromium.
The research has found that the removal efficiency of MB was lower than
OPMF; whereas, the multiple metals ions removal efficiency decreased in
the order of Pb2+ > Cu2+ > Ni2+ > Cr2+.

Matched MeSH terms: Chromium
Fulltext Mechanisms of removal of heavy metal ions by ZnO particles

Le AT, Pung SY, Sreekantan S, Matsuda A, Huynh DP

Heliyon, 2019 Apr;5(4):e01440.
PMID: 31008388 DOI: 10.1016/j.heliyon.2019.e01440

Effluent discharges from industry and domestic waste containing unknown inorganic pollutants. In this work, different mechanisms of heavy metal ions removal using ZnO particles were studied. ZnO particles were synthesized using solid precipitation technique. The morphology of ZnO particles was rod-like shape. The average length and diameter of ZnO particle were 497.34 ± 15.55 and 75.78 ± 10.39nm, respectively. These particles removed effectively heavy metal ions such as Cu(II), Ag(I) and Pb(II) ions with efficiency >85% under exposure of 1 hour of UV light. However, poor removal efficiency, i.e. <15% was observed for Cr(VI), Mn(II), Cd(II) and Ni(II) ions. The removal of these heavy metal ions was in the forms of metals or metal oxide via reduction/oxidation or adsorption mechanism.

Matched MeSH terms: Chromium
Fulltext Post-implantation Deformation of Titanium Rod and Cobalt Chrome Rod in Adolescent Idiopathic Scoliosis

Sia U, Tan BB, Teo YY, Wong CC

Malays Orthop J, 2019 Mar;13(1):14-19.
PMID: 31001378 DOI: 10.5704/MOJ.1903.002

Introduction: Post-implantation rod deformation is anticipated in scoliosis surgery but the difference in rod deformation between titanium and cobalt chrome rod has not been elucidated. This study aims to compare the difference in rod deformation between two groups. Materials and Methods: Twenty-one adolescent idiopathic scoliosis (AIS) patients were recruited from a single center. The over-contoured concave rods were traced prior to insertion. Post-operative sagittal rod shape was determined from lateral radiographs. Rod deformation was determined using maximal rod deflection and angle of the tangents to rod end points. The differences between pre- and post-operative rod contour were analysed statistically. Rod deformation and thoracic kyphosis between two types of implants were analysed. Results: Both rods exhibited significant change of rod angle and deflection post-operatively. Curvature of the titanium rod and cobalt chrome rod decreased from 60.5° to 37°, and 51° to 28° respectively. Deflection of titanium rod and cobalt chrome rod reduced from 28mm to 23.5mm and 30mm to 17mm respectively. There was no significant difference between titanium and cobalt chrome groups with regard to rod angle (p=0.173) and deflection (p=0.654). Thoracic kyphosis was increased from 20° to 26° in titanium group but a reduction from 25° to 23° was noticed in cobalt chrome group, but these findings were not statistically significant. Conclusion: There was no statistical difference in rod deformation between the two groups. Thus, the use of titanium rod in correction of sagittal profile is not inferior in outcome compared with cobalt chrome but with lower cost.

Matched MeSH terms: Chromium Alloys
Formation of grassy TiO2 nanotube thin film by anodisation in peroxide electrolyte for Cr(VI) removal under ultraviolet radiation

Taib MAA, Alias N, Jaafar M, Razak KA, Tan WK, Shahbudin IP, et al.

Nanotechnology, 2020 Oct 23;31(43):435605.
PMID: 32640434 DOI: 10.1088/1361-6528/aba3d8

Arrays of TiO2 nanotubes (TiO2 NTs) with grassy surfaces were observed on titanium foil anodised at 60 V in fluorinated ethylene glycol (EG) with added hydrogen peroxide (H2O2). The grassy surface was generated by the chemical etching and dissolution of the surface of the TiO2 NTs walls, which was accelerated by the temperature increase on the addition of H2O2 . Upon annealing at 600 °C, the grassy part of the TiO2 NTs was found to consist of mostly anatase TiO2 whereas the bottom part of the anodic oxide comprised a mixture of anatase and rutile TiO2. The TiO2 NTs were then used to reduce hexavalent chromium (Cr(VI)) under ultraviolet radiation. They exhibited a rather efficient photocatalytic effect, with 100% removal of Cr(VI) after 30 min of irradiation. The fast removal of Cr(VI) was due to the anatase dominance at the grassy part of the TiO2 NTs as well as the higher surface area the structure may have. This work provides a novel insight into the photocatalytic reduction of Cr(VI) on grassy anatase TiO2 NTs.

Matched MeSH terms: Chromium
Simultaneous photocatalytic reduction of hexavalent chromium and oxidation of p-cresol over AgO decorated on fibrous silica zirconia

Aziz FFA, Jalil AA, Hassan NS, Fauzi AA, Azami MS

Environ Pollut, 2021 Sep 15;285:117490.
PMID: 34091265 DOI: 10.1016/j.envpol.2021.117490

The co-existence of heavy metals and organic compounds including Cr(VI) and p-cresol (pC) in water environment becoming a challenge in the treatment processes. Herein, the synchronous photocatalytic reduction of Cr(VI) and oxidation of pC by silver oxide decorated on fibrous silica zirconia (AgO/FSZr) was reported. In this study, the catalysts were successfully developed using microemulsion and electrochemical techniques with various AgO loading (1, 5 and 10 wt%) and presented as 1, 5 and 10-AgO/FSZr. Catalytic activity was tested towards simultaneous photoredox of hexavalent chromium and p-cresol (Cr(VI)/pC) and was ranked as followed: 5-AgO/FSZr (96/78%) > 10-AgO/FSZr (87/61%) > 1-AgO/FSZr (47/24%) > FSZr (34/20%). The highest photocatalytic activity of 5-AgO/FSZr was established due to the strong interaction between FSZr and AgO and the lowest band gap energy, which resulted in less electron-hole recombination and further enhanced the photoredox activity. Cr(VI) ions act as a bridge between the positive charge of catalyst and cationic pC in pH 1 solution which can improve the photocatalytic reduction and oxidation of Cr(VI) and pC, respectively. The scavenger experiments further confirmed that the photogenerated electrons (e-) act as the main species for Cr(VI) to be reduced to Cr(III) while holes (h+) and hydroxyl radicals are domain for photooxidation of pC. The 5-AgO/FSZr was stable after 5 cycles of reaction, suggesting its potential for removal of Cr(VI) and pC simultaneously in the chemical industries.

Matched MeSH terms: Chromium
Synthesis of Iron Oxide@Pt Core-Shell Nanoparticles for Reductive Conversion of Cr(VI) to Cr(III) and Antibacterial Studies

Sivaranjan K, Santhanalakshmi J, Panneer DS, Vivekananthan S, Sagadevan S, Johan MRB, et al.

J Nanosci Nanotechnol, 2020 02 01;20(2):918-923.
PMID: 31383087 DOI: 10.1166/jnn.2020.16895

Herein, we report the facile synthesis of Iron oxide@Pt core-shell nanoparticles (NPs) by facile two step synthesis process. The first step follows the growth of iron oxide nanoparticle by thermal decomposition process while the second step deals with the formation of iron oxide@Pt core-shell nanoparticles by the chemical reduction method. The synthesized core-shell nanoparticles were characterized by several techniques and used for the catalytic reductive translation of Cr(VI) to Cr(III) in the presence of formic acid by a UV-vis spectrophotometer. The UV photo-spectrometer analysis confirmed the conversion efficiency from 12% to as high as 98.8% at the end of 30 minutes. Thus, the presence of Iron oxide @Pt core-shell nanoparticles (NPs) can be effectively used as a catalyst for the reducion of Cr(VI) to Cr(III) ions. Additionally, antibacterial studies were performed for the prepared core-shell nanoparticles against two bacterial strains, i.e., gram (+ve) Staphylococcus Aureus (S. Aureus) and gram (-ve) Escherichia Coli (E. Coli).

Matched MeSH terms: Chromium
Fulltext Isolation and Characterisation of a Molybdenum-reducing and Metanil Yellow Dye-decolourising Bacillus sp. strain Neni-10 in Soils from West Sumatera, Indonesia

Mansur R, Gusmanizar N, Roslan MA, Ahmad SA, Shukor MY

Trop Life Sci Res, 2017 Jan;28(1):69-90.
PMID: 28228917 MyJurnal DOI: 10.21315/tlsr2017.28.1.5

A molybdenum reducing bacterium with the novel ability to decolorise the azo dye Metanil Yellow is reported. Optimal conditions for molybdenum reduction were pH 6.3 and at 34°C. Glucose was the best electron donor. Another requirement includes a narrow phosphate concentration between 2.5 and 7.5 mM. A time profile of Mo-blue production shows a lag period of approximately 12 hours, a maximum amount of Mo-blue produced at a molybdate concentration of 20 mM, and a peak production at 52 h of incubation. The heavy metals mercury, silver, copper and chromium inhibited reduction by 91.9, 82.7, 45.5 and 17.4%, respectively. A complete decolourisation of the dye Metanil Yellow at 100 and 150 mg/L occurred at day three and day six of incubations, respectively. Higher concentrations show partial degradation, with an approximately 20% decolourisation observed at 400 mg/L. The bacterium is partially identified based on biochemical analysis as Bacillus sp. strain Neni-10. The absorption spectrum of the Mo-blue suggested the compound is a reduced phosphomolybdate. The isolation of this bacterium, which shows heavy metal reduction and dye-decolorising ability, is sought after, particularly for bioremediation.

Matched MeSH terms: Chromium
Association between respirable hexavalent chromium (Cr-VI) compounds with urinary β2-microglobulin level of welders in an automotive components manufacturing plant

Shamsul, B.S., Zakirah, M.

Journal of Occupational Safety and Health, 2014;11(1):23-32.
MyJurnal

The main objective of this study is to determine the association between respirable hexavalent chromium compounds with urinary β2-microglobulin levels among welders in an automotive components manufacturing plant. 49 welders and 39 workers involved in stamping process were selected as the exposed and the comparative group. β2-microglobulin is a protein renal tubular dysfunction marker that can indicate renal dysfunction caused by heavy metal. Air samples of worker’s breathing zone were collected using personal air sampling pump and filter papers. Filter papers were then diluted and analysed with Atomic Absorption Spectrophotometry (AAS). Workers’ urine samples were collected at the end of 8-hour work shift and analysed with β2-microglobulin ELISA Kit (IBL-Hamburg) and a microtiter reader. Meanwhile, creatinine levels were analysed with creatinine test strips and Reflotron®. A mean concentration of respirable hexavalent chromium compounds in air for the exposed group was 0.135 ± 0.043μg/m3 while for the non-exposed group was 0.124 ± 0.029μg/m3. The mean level of urinary β2-microglobulin per creatinine for the exposed group was 84.996 ± 39.246μg/g while that of the comparative group was 61.365 ± 21.609μg/g. The concentrations of respirable hexavalent chromium compounds were higher in the exposed group compared to the comparative group (Z=-2.444, p=0.015). β2-microglobulin level was also higher in the exposed group compared to the non-exposed group (t=3.821, p=

Matched MeSH terms: Chromium
Spectrophotometric determination of germanium with Catechol Violet and cetyltrimethylammonium bromide

Leong CL

Talanta, 1971 Aug;18(8):845-8.
PMID: 18960953

A ternary complex between germanium, Catechol Violet (CV) and cetyltrimethylanunoniuni bromide is proposed for the determination of germanium. The stoichiometric ratio Ge:CV is 1:2. Beer's law is obeyed from 0.1 to 1.0 ppm of Ge. The method is highly selective. Interference from Sn(IV), Fe(III), Bi(III), Cr(VI), Mo(VI), V(V) and Sb(III) in mg amounts is eliminated by extracting the germanium into carbon tetrachloride from 9M HC1 and then stripping into water before the photometric determination.

Matched MeSH terms: Chromium
Fulltext Physico-chemical and electrical properties of bismuth chromate solid solutions

Tan, Y.P., Wong, Y.C.

Pertanika Journal of Science & Technology, 2013;21(1):97-110.
MyJurnal

Bismuth chromium solid solutions, with a general formula Bi6-xCr2Oδ, where -1 ≤ x ≤ 2, were successfully synthesized via the conventional solid state method. The phases of the synthesized samples were determined by X-ray diffraction (XRD) analysis. The properties of single-phase compounds were characterized by using differential thermal analysis (DTA), thermal gravimetric analysis (TGA), AC impedance spectroscopy, and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The occurrence of phase transitions was confirmed by DTA and TGA, where a thermal event was observed by DTA at around 800oC. In addition, TGA studies also showed that there was a weight loss at around 800oC. Elemental analysis of Bi6Cr2O15 and its solid solutions by ICP-AES showed a good agreement between the expected value and the experimental value on the compositions, with no evidence of any systematic deviation from stoichiometric. Electrical properties of Bi6Cr2O15 and its solid solutions were investigated by using AC impedance spectroscopy from 300oC to 650oC. Ionic conductivity increased with the increasing temperature and bismuth content, and the best ionic conductivity was observed for Bi7Cr2O16.5. The activation energy (Ea) of Bi6Cr2O15 and its solid solutions were in the range of 1.22-1.32 eV.

Matched MeSH terms: Chromium
Pyrus pyrifolia fruit peel as sustainable source for spherical and porous network based nanocellulose synthesis via one-pot hydrolysis system

Chen YW, Hasanulbasori MA, Chiat PF, Lee HV

Int J Biol Macromol, 2019 Feb 15;123:1305-1319.
PMID: 30292586 DOI: 10.1016/j.ijbiomac.2018.10.013

In the present study, we attempted revalorization of pear (Pyrus pyrifolia L.) peel residue into high value-added nanomaterials. A green and facile one-pot isolation procedure was designed to simplify the isolation process of nanocellulose directly from pear peel residue. The one-pot approach employed in this work is interesting as the reaction involved less harmful chemicals usage and non-multiple steps. The reaction was carried out by adding hydrogen peroxide as an oxidant and chromium (III) nitrate as catalyst in the acidic medium under mild process conditions. FTIR spectroscopy proved that the pear peel derived nanocellulose was purely cellulose phases without the presence of non-cellulosic layer. XRD study indicated that the isolated nanocellulose possessed of cellulose I polymorph with high crystallinity index of 85.7%. FESEM analysis clearly revealed that the considerable size reduction during one-pot process. Remarkably, TEM analysis revealed that the isolated nanocellulose consisted of network-liked nature and spherical shaped morphologies with high aspect ratio of 24.6. TGA showed nanocellulose has lower thermal stability compared to pear peel residue. This study provided a cost-effective method and straightforward one-pot process for fabrication of nanocellulose from pear peel residue. This is the first investigation on the nanocellulose extraction from pear fruit.

Matched MeSH terms: Chromium
Adsorption mechanism of hexavalent chromium onto layered double hydroxides-based adsorbents: A systematic in-depth review

Tran HN, Nguyen DT, Le GT, Tomul F, Lima EC, Woo SH, et al.

J Hazard Mater, 2019 07 05;373:258-270.
PMID: 30925385 DOI: 10.1016/j.jhazmat.2019.03.018

An attempt has been made in this review to provide some insights into the possible adsorption mechanisms of hexavalent chromium onto layered double hydroxides-based adsorbents by critically examining the past and present literature. Layered double hydroxides (LDH) nanomaterials are typical dual-electronic adsorbents because they exhibit positively charged external surfaces and abundant interlayer anions. A high positive zeta potential value indicates that LDH has a high affinity to Cr(VI) anions in solution through electrostatic attraction. The host interlayer anions (i.e., Cl-, NO3-, SO42-, and CO32-) provide a high anion exchange capacity (53-520 meq/100 g) which is expected to have an excellent exchangeable capacity to Cr(VI) oxyanions in water. Regarding the adsorption-coupled reduction mechanism, when Cr(VI) anions make contact with the electron-donor groups in the LDH, they are partly reduced to Cr(III) cations. The reduced Cr(III) cations are then adsorbed by LDH via numerous interactions, such as isomorphic substitution and complexation. Nonetheless, the adsorption-coupled reduction mechanism is greatly dependent on: (1) the nature of divalent and trivalent salts utilized in LDH preparation, and the types of interlayer anions (i.e., guest intercalated organic anions), and (3) the adsorption experiment conditions. The low Brunauer-Emmett-Teller specific surface area of LDH (1.80-179 m2/g) suggests that pore filling played an insignificant role in Cr(VI) adsorption. The Langmuir maximum adsorption capacity of LDH (Qomax) toward Cr(VI) was significantly affected by the natures of used inorganic salts and synthetic methods of LDH. The Qomax values range from 16.3 mg/g to 726 mg/g. Almost all adsorption processes of Cr(VI) by LDH-based adsorbent occur spontaneously (ΔG° <0) and endothermically (ΔH° >0) and increase the randomness (ΔS° >0) in the system. Thus, LDH has much potential as a promising material that can effectively remove anion pollutants, especially Cr(VI) anions in industrial wastewater.

Matched MeSH terms: Chromium
Fulltext Removal of Heavy Metal Ions with Acid Activated Carbons Derived from Oil Palm and Coconut Shells

Rahman MM, Adil M, Yusof AM, Kamaruzzaman YB, Ansary RH

Materials (Basel), 2014 May 07;7(5):3634-3650.
PMID: 28788640 DOI: 10.3390/ma7053634

In this work, batch adsorption experiments were carried out to investigate the suitability of prepared acid activated carbons in removing heavy metal ions such as nickel(II), lead(II) and chromium(VI). Acid activated carbons were obtained from oil palm and coconut shells using phosphoric acid under similar activation process while the differences lie either in impregnation condition or in both pretreatment and impregnation conditions. Prepared activated carbons were modified by dispersing hydrated iron oxide. The adsorption equilibrium data for nickel(II) and lead(II) were obtained from adsorption by the prepared and commercial activated carbons. Langmuir and Freundlich models fit the data well. Prepared activated carbons showed higher adsorption capacity for nickel(II) and lead(II). The removal of chromium(VI) was studied by the prepared acid activated, modified and commercial activated carbons at different pH. The isotherms studies reveal that the prepared activated carbon performs better in low concentration region while the commercial ones in the high concentration region. Thus, a complete adsorption is expected in low concentration by the prepared activated carbon. The kinetics data for Ni(II), Pb(II) and Cr(VI) by the best selected activated carbon fitted very well to the pseudo-second-order kinetic model.

Matched MeSH terms: Chromium
An assessment of the pH changes and metal ions released into artificial saliva by fake orthodontic braces

Haleem R, Shafiai NAA, Noor SNFM

BMC Oral Health, 2023 Sep 16;23(1):669.
PMID: 37717000 DOI: 10.1186/s12903-023-03339-7

BACKGROUND: This present study assesses changes in the pH as well as the metal ions that fake braces release into artificial saliva (AS) using a pH meter and inductively coupled plasma atomic emission spectroscopy (ICP-AES), respectively.
METHODS: Three sets of fake archwires (AWs) and brackets (Bs) as well as a set of controls were immersed in AS and placed in an incubator shaker at 50 rpm and 37°C. At Days 0, 1, 7, 14, 21, and 28, the pH of the AS medium was measured and 3.0 ml of AS was collected and stored at -20°C for elemental analysis.
RESULTS: Significant changes in pH were observed on Days 0, 1, 7, 14, 21, and 28 in the AS of the AW group. However, these changes were only observed in the B group on Days 0 and 7. The fake samples released a large quantity of sodium (Na), potassium (K), and calcium (Ca) ions, at concentrations exceeding 100 mg/L, post-28 days of immersion. The control and fake braces samples released other ions; such as lithium (Li), magnesium (Mg), barium (Ba), chromium (Cr), copper (Cu), lead (Pb), and aluminium (Al); at concentrations that did not exceed 10 mg/L.
CONCLUSIONS: The pH of the AS of all the samples increased post-incubation. Only 10 ions; namely, Na, Li, K, Mg, Ca, Ba, Cr, Cu, Pb, and Al; were detected in the AS.

Matched MeSH terms: Chromium
Bacterial reduction of Cr(VI) at technical scale--the Malaysian experience

Zakaria ZA, Ahmad WA, Zakaria Z, Razali F, Karim NA, Sum MM, et al.

Appl Biochem Biotechnol, 2012 Jul;167(6):1641-52.
PMID: 22350941 DOI: 10.1007/s12010-012-9608-9

The bacterial reduction of Cr(VI) from industrial wastewater was evaluated using a 2.0-m(3) bioreactor. Liquid pineapple waste was used as a nutrient for the biofilm community formed inside the bioreactor. The use of rubber wood sawdust as packing material was able to immobilize more than 10(6) CFU mL(-1) of Acinetobacter haemolyticus cells after 3 days of contact time. Complete reduction of 15-240 mg L(-1) of Cr(VI) was achieved even after 3 months of bioreactor operation. Cr(VI) was not detected in the final effluent fraction indicating complete removal of Cr from solution from the flocculation/coagulation step and the unlikely re-oxidation of Cr(III) into Cr(VI). Impatiens balsamina L. and Gomphrena globosa L. showed better growth in the presence of soil-sludge mixture compared to Coleus scutellarioides (L.) Benth. Significant amounts of Cr accumulated at different sections of the plants indicate its potential application in Cr phytoremediation effort. The bacterial-based system was also determined not to be detrimental to human health based on the low levels of Cr detected in the hair and nail samples of the plant operators. Thus, it can be said that bacterial-based Cr(VI) treatment system is a feasible alternative to the conventional system especially for lower Cr(VI) concentrations, where sludge generated can be used as growth supplement for ornamental plant as well as not detrimental to the health of the workers.

Matched MeSH terms: Chromium/metabolism*
Removal of chromium hexavalent ion from aqueous solutions using biopolymer chitosan coated with poly 3-methyl thiophene polymer

Hena S

J Hazard Mater, 2010 Sep 15;181(1-3):474-9.
PMID: 20627405 DOI: 10.1016/j.jhazmat.2010.05.037

Adsorption capacity of Cr(VI) onto chitosan coated with poly 3-methyl thiophene synthesized chemically was investigated in a batch system by considering the effects of various parameters like contact time, initial concentration, pH and temperature. Cr(VI) removal is pH dependent and found to be maximum at pH 2.0. Increases in adsorption capacity with increase in temperature indicate that the adsorption reaction is endothermic. Based on this study, the thermodynamic parameters like standard Gibb's free energy (DeltaG degrees), standard enthalpy (DeltaH degrees) and standard entropy (DeltaS degrees) were evaluated. Adsorption kinetics of Cr(VI) ions onto chitosan coated with poly 3-methyl thiophene were analyzed by pseudo-first-order and pseudo-second-order models. The Langmuir, Freundlich and Temkin isotherms were used to describe the adsorption equilibrium studies of chitosan coated with poly 3-methyl thiophene at different temperatures. Langmuir isotherm shows better fit than Freundlich and Temkin isotherms in the temperature range studied. The results show that the chitosan coated with poly 3-methyl thiophene can be efficiently used for the treatment of wastewaters containing chromium as a low cost alternative compared to commercial activated carbon and other adsorbents reported. In order to find out the possibility of regeneration and reuse of exhausted adsorbent, desorption studies were also performed.

Matched MeSH terms: Chromium/isolation & purification*
Pilot-scale removal of chromium from industrial wastewater using the ChromeBac system

Ahmad WA, Zakaria ZA, Khasim AR, Alias MA, Ismail SM

Bioresour Technol, 2010 Jun;101(12):4371-8.
PMID: 20185301 DOI: 10.1016/j.biortech.2010.01.106

The enzymatic reduction of Cr(VI) to Cr(III) by Cr(VI) resistant bacteria followed by chemical precipitation constitutes the ChromeBac system. Acinetobacter haemolyticus was immobilized onto carrier material inside a 0.2m(3) bioreactor. Neutralized electroplating wastewater with Cr(VI) concentration of 17-81 mg L(-1) was fed into the bioreactor (0.11-0.33 m(3)h(-1)). Complete Cr(VI) reduction to Cr(III) was obtained immediately after the start of bioreactor operation. Together with the flocculation, coagulation and filtration, outflow concentration of less than 0.02 mg Cr(VI)L(-1) and 1mg total CrL(-1) were always obtained. Performance of the bioreactor was not affected by fluctuations in pH (6.2-8.4), Cr(VI) (17-81 mg L(-1)), nutrient (liquid pineapple waste, 1-20%v/v) and temperature (30-38 degrees C). Standby periods of up to 10 days can be tolerated without loss in activity. A robust yet effective biotechnology to remove chromium from wastewater is thus demonstrated.

Matched MeSH terms: Chromium/isolation & purification*

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