Lee, C. K.

Low, K. S.

Universiti Putra Malaysia Institutional Repository

FOR Category Fl0300: Chemical SciencesTHE USE OF LOW COST MATERIALS FORREMOVAL OF TOXIC POLLUTANTS FROMAQUEOUS ENVIRONMENTK.S. Low and C.K. LeeFaculty of Science and Environmental StudiesUniversiti Putra Malaysia, 43400 UPM, Serdang, Selangor,MalaysiaKeywords: sorption, low cost sorbents, modifications,organic and inorganic pollutants.IntroductionThe removal or reduction of organic and inorganic pollutantsfrom industrial wastewaters could be achieved by using ion-exchangers or activated carbon. However, these materialsare expensive and altemative must be sought especially inless developed countries. Various low-cost biological materi-als have been investigated for this purpose (Sharma and For-ster, 1995; Low et al. 1995). To enhance their sorption ca-pacities various chemical modifications on the sorbents wereattempted (Low et al. 1996; Low et al. 1997). N-(3-chloro-2-hydroxypropyl)-trimethylammonium chloride was used toconvert the surface hydroxyl groups to quaternary ammo-nium salt. This effectively converts the sorbent into anionexchangers. Their applications in removing acid dyes (tex-tile effluent) and chromate (electroplating waste) were stud-ied under both batch and continuous flow conditions. Sor-bents studied include coconut and rice hulls as these materi-als possess high silica content, which in tum provides goodmechanical strength.Materials and MethodsRice hulls (coconut hulls) were ground to 1 mm size. Theywere modified according to the method reported by Laszlo(1996). In the batch experiments 0.1 g of sorbent in 20 ml ofsolution was agitated at ISO rpm at 2S±2°C for variouslengths of time. The sorbent mixture was centrifuged and thefiltrate was analysed for its content. In the case of Cr(VI) theelement was determined using an inductively coupledplasma-atomic emission spectrometer. When reactive dyeswere used their concentrations was established using a spec-trophotometer (Hitachi U20000) at the appropriate wave-lengths of the dyes. In the column study a glass column of1.0cm diameter packed with the relevant sorbent at variousbed depths was used. Flow rates were adjusted using a peri-staltic pump. Aliquots were collected and the analyte con-tents were determined. Per cent uptake is defined as «Co-Ct)/Co)x100where Co and C, are the initial and at time (t) ofthe analyte concentrations respectively. Textile waste wascollected from Kemunting Textile Industries, Perak andchrome waste from Dole Electroplating Plant in Senawang,Seremban.Results and DiscussionSorption of Cr(VI) by quaternised rice hulls(QRH) and coco-nut husks(QCH). The sorption is essentially an ion-exchangebetween the negatively charged Cr(VI) oxyanions and thechloride group of the quaternary amine. The high sorptioncapacity of both modified materials across a wide range ofpH means that the removal of Cr(VI) could be effectivelycarried out without having to adjust the pH of the solution asis necessary in the case of most other biological materials.The sorption was rapid and equilibrium was established inless than 30 min indicating that the sorbents are useful incontinuous flow study, where the contact time between sor-bate and sorbent is generally short. The maximum sorptioncapacities of QRH and QCH for Cr(VI) were 32.3 3S.2mg/g respectively. These values were extrapolated fromLangmuir isotherms. The monovalent anions had very littlevery little effect on the sorption capacity of QRH at levelsbelow 1molar. The order of suppressing effect of the anionson the Cr(VI) uptake by QRH is phosphatee-sulphate»EDTAc-chloride, nitrate. The results of a flow study whichcontained a mixed bed of NRH and QRH showed that bothCu(II) and Cr(VI) could be successfully removed from elec-troplating waste. Sorption of reactive dyes by QRH and QGHwithout quaternisation both RH and GH had no affinity forreactive dyes. Their sorption capacities were greatly en-hanced through quaternisation. Maximum sorption capaci-ties for Reactive Blue 2 for QRH and QCH were 130 and128.9 mg/g respectively. The sorption of hydrolysed Reac-tive Blue 2 on QRH and RCH was practically unaffected bythe presence of sulphate and carbonate except when the con-centration reached I M. NaCl did not show any effect up toa concentration of 1 M, while increasing NaOH concentra-tion progressively decreased the binding capacity of theQRH.The capability of the QRH and QCH to remove reactive dyesfrom a textile mill effluent was investigated. There was a97% reduction in dye concentration after treatment.ConclusionsThe results show that quaternised rice hulls and coconuthusks were more effective than the corresponding untreatedmaterials in removing Cr(VI) and reactive dyes over abroader pH range. This provides a wider workable pH rangethan had ever been reported for the removal of Cr(VI) inwastewater. Cr(VI) and Cu(II) from an electroplating wastewithout pretreatment could be successfully removed or re-duced under continuous flow study.ReferencesLaszlo, I.A. 1996. Electrolyte effects on hydrolyzed reactive dye toquaternized cellulose. Textile Chemist and Colorist. 27(4): 25-27.Low, KS., Lee, C.K and Tan, K.K. 1995. Biosorption of basic dyesby water hyacinth roots. Biores. Technol. 52: 79-83.,Low, KS., Lee, C.K. and Tan, Cd.. 1996. Enhancement of coppersorption through Acid Blue 29 treated palm pressed fibres. 4(1):41-50.Low, KS., Lee, C.K. and Lee, L.L. 1997. Chromium (III) sorptionenhancement through NTA-modification of biological materials.Bull. Environ. Contam. Toxico!. 58: 380-386.Sharma, D.C. and Forster, C.F. 1995. Column studies into the ad-sorption of chromium(VI) using sphagnum moss peat. Biores.Techno!. 52: 261-267.Supported by IRPA Grant 09-02-04-0061249

The use of low cost materials for removal of toxic pollutants from aqueous environment

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The use of low cost materials for removal of toxic pollutants from aqueous environment

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