Abstract
This paper presents the potential application of macadamia nut shells (MNS) in the bio-sorption of fluoride and its antimicrobial potency against common pathogens encountered in surface water resources. The efficiency of MNS in the sorption of fluoride was determined using batch mode experiments, while the antimicrobial potency was investigated using the well disc diffusion assay method. The maximum fluoride sorption capacity of 1.26 mg/g was recorded at an initial fluoride concentration of 5 mg/L, adsorbent dosage of 0.5 g/100 mL, contact time of 120 min and initial pH of 6. The adsorption kinetics data were better described with a pseudo second order model, indicating the dominance of the chemisorption mechanisms. The Langmuir adsorption isotherm model described the isotherm data suggesting a monolayered adsorption. The thermodynamic parameters, ∆Gº and ∆Hº, confirmed that F− sorption by MNS is a spontaneous and endothermic process. The bio-sorbent was regenerated for seven continuous cycles when HCl was used as regenerating solution. The antimicrobial studies revealed that MNS has minimal activity towards Escherichia coli, Staphylococcus aureus and Klebsiella pneumoniae. The MNS showed potentials for application in bio-sorption of fluoride. However, the doping of MNS with metal ions is recommended to enhance its anti-microbial potency.
Highlights
Adsorben2t School of CAhdemsoisrtrpytaiondnMCaatepraiacliStcyie(nmceg, T/gec)hnical UniversitypofHKenya, Haile Selassie Avenue, Ref pH Sugarcane bagasPs.eO
Macadamia nuctosnhceelnlstration of 5 mg/L, 1a.d2s6orbent dosage of 0.5 g/100 mL6, contact time of 120 min aTnhdisinsittuiadly pH of 6T.hTishsetauddsyorption kinetics data were better described with a pseudo second order model, indicating th3e.2d.5o.mAindasnocreptoifotnheTchheermmiosodrypntiaomn imcsechanisms
This study evaluated the physicochemical characteristics of ma6cadamia nut shells (MNS) and its application towards the removal of fluoride and pathogens from water
Summary
Adsorben2t School of CAhdemsoisrtrpytaiondnMCaatepraiacliStcyie(nmceg, T/gec)hnical UniversitypofHKenya, Haile Selassie Avenue, Ref pH Sugarcane bagasPs.eO. The Langmuir adsorption isotherm model describedTthheerimsoothdeyrmnadmaitcassupgagreasmtinetgerasm, souncohlayaesretdheadGsoirbpbtsione.neTrhgeythcehramnogdeyn(∆amGioc), enthal arameters, such as the Gibbs. The MNS showed dlnopKing=of−M∆RNHTS w+it∆hRSmetal ions is potentials for recommended (1 where ∆Go is the Gibbs free energy change (KJ/mol), R is the gas constant with the val ree energmya1c5h03a1n06g5e (KJ/mol), R is the gaKseycownosrtdasn: taonwft8iimt.h3i1ct4rhoeJbimvalaoplluo−1etKen−c1ya;nbdio-Tsoirspatibosno;lcuhteemteismorppetiroant;uflrueoirnidKe;emlvainca.dKacmiisatnhuet dshimellesnsionless equ is absoluAtceadteemmic pEdeirtoart: uArgaetain Kelvin. Kc is the dimelnibsriiounmlescsoenqsutain- t determined from the Langmuir constant (KL). 1/T shows the plot, while the constant parameters are pr nst 1/T sPhuoblwishsedt:h29eJapnluoarty, 2w02h2 ile the constantRpuararal msceoenmtteemrdsuianrietTieapsbrlieen-7m. The ∆Ho value was found to be poswitiidvee,swuhffiecrthhfeirnopdmricoaflcteuessosrtfihdoaret sroerlaptteiodnilolnf efsluseosriadnedbyabMouNtS3.i4s menidlloiothneprmeoicplieninnadtuervee.loApninegndotherm of fluoride by MNS is endothermic inconuantturriees. Ide range of defluoridation technologies based on the principles of ion-exchange, conditions of the Creative Commons adsorption, co-precipitation, membrane and electrodialysis techniques have been devel- Ampnarionecnleydsysootshuuengrggmecishctsildchreenmdisieorepvteiorynyreeaarctfiroonms [p3a0t]h. oTgheisnirseilnatelidnedwiseitahsetsh.eTfhinisdcinagllss of adsor orption rCeoapcytriioghnts: [©302]0.22Thbyisthies ainuthloinrse. wfitohr tdheevfeinlodptiinmognesnkotinfoeaftdiicsnsonrsoptuv-datyi,vwe hmicahtesrhiaolws etdhabtecttaenr fsiitmtinugltsatnoeposuesulydoresmecoovnedflourdoerridmeoadnedl of reacti h showedLibceentsteeerMfiDttPiIn, gBsasteol, pSwseituzedrloansde. conpdatohrodgeernmfkrooidnmeeltdoicfrsir.neTkahicnteigopnwosaitteivreinvlailnueew∆iStho stuhgegseussttianignaabdleisdsoecviealtoivpemaednstogrpotailosntamrgeecth6a.n1i,sm as w lue ∆So sTuhgisgaertsictlienigs aan dopiesnsoacccieastsiavreticaledsowrphtiicohnamimecsahsaattnhiimesmprarnoasvdiownmgelaldcicsetrsisbtuoticolneaonf dflruinorkiidnegiwonasteornbtyh2e0s3u0r.face of MNS [30]. on of fluodrisitdribeuiteodnsunodnerththeesuterrfmasceanodf MNS [3A0]w. ide range of defluoridation technologies based on the principles of ion-exchange, conditions of the Creative Commons adsorption, co-precipitation, membrane and electrodialysis techniques have been devel-
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