Phycoremediation of heavy metals and resource recovery of rare earth elements using green algae from eutrophic freshwater bodies

Abstract

English: Biosorption is an emerging and or complementary technology to the conventional treatment methods for industrial wastewater. Biosorption involves the use of dead biological material to sequester inorganics and or organic pollutants. Micro algae have a diversity of algal species found mostly in freshwater bodies of which only a few were investigated for their biosorption potential. This study focussed on the utilisation of green algal sorbents for the recovery of rare earth elements (REE) and removal of heavy metals. The algal samples were collected from Hartbeespoort dam in South Africa and isolated using streak plating method. The pure algal species were identified using molecular methods and found to have 95-98% identities to Chloroidium saccharophilum, Desmodesmus multivariabilis, Scenedesmus acuminutus and Stichococcus bacillaris. Chlorella vulgaris and Chlamydomonas reinhardtii were purchased for comparison purposes. The species were cultured in the laboratory under controlled conditions and dried to obtain dead algal cells for biosorption studies. Adsorption and desorption experiments were carried out to determine the sorption capacity and possible recovery in single metallic studies of lanthanum (La), thallium (Tl) and cadmium (Cd). Kinetic studies were also investigated to determine the potential rate controlling steps that are useful when designing a full scale biosorption process. Surface characterisation of algae was carried out to determine the possible mechanisms involved in biosorption processes. Multi-metallic studies were investigated to better understand the influence of competing ions in the actual environment.

Sepedi: Tlošodikhemikhale ke theknolotši ye e tšwelelago le goba yeo e tlaleletšago mekgwa ye e tlwaelegilego ya tlhwekišo ya meetse a ditšhila a intasteri. Tlošodikhemikhale e akaretša tšhomišo ya didirišwa tša thutaphelo tše di hwilego go swara dilo tše di sa phelego le goba diphedi tša go tšhilafatša. Di-alkae tše nnyane di na le mehuta yeo e fapafapanego ya boalgale yeo e hwetšwago kudu ka boteng bja meetse a hlwekilego moo go lego tše mmalwa fela tšeo bokgoni bja tšona bja payopene bo nyakišišitšwego, Dinyakišišo tše di lebeletše kudu tšhomišo ya didirwa tša go monya bolele bjo botala bakeng sa go bušetša dielemente tša lefase tše hlokagalago (REE) le go tloša dimetale tše boima. Disampole tša algale di kgobokeditšwe go tšwa letamong la Hartbeespoort ka Afrika Borwa gomme tša aroganywa ka go šomiša mokgwa wa go poleita ka distriki. Mehuta ya algal ye e hlwekilego e ile ya hlaolwa ka go šomiša mekgwa ya dimolekule gomme ya hwetšagala e na le 95-98% ya boitšhupo go Khloroidiamo sakharofilamo, Desmodesmas multivarayabilis, Scenedesmus akhuminutus le Stikhokhokhase basilarisi. Kholorella vulkarisi le Chlamydomonas reinhardtii di rekilwe bakeng sago bapetša. Mehuta e ile ya godišwa ka laboratoring ka fase ga maemo a laolwago gomme ya omišwa go hwetša disele tša alkale tše di hwilego bakeng sa dithuto tša payopšene. Diteko tša go monya le go monyolla di dirilwe go bona bokgoni bja semonyi le kgonagalo ya go bušetsa thutong e tee ya dimetaliki tša lanthanum (La), thallium (Tl) le cadmium (Cd). Dinyakišišo tša mosepelo di ile tša nyakišišwa gape go lekola magato a go laola magato a ka bago le mohola ge go hlangwa tshepedišo ya payopšene ya tekanyo ye e tletšego. Tlhalošo ya bokagodimo ya algae e ile ya phethwa go bona mekgwa ye e kgonegago yeo e amegago ka ditshepedišong tša payopšene . Dinyakišišo tše ntši tša dimetale di ile tša nyakišišwa go kwešiša bokaone khuetšo ya di-ion tša phadišano tikologong ya kgonthe.

Afrikaans: Biosorpsie is 'n opkomende en komplementêre tegnologie tot die konvensionele behandelingsmetodes vir industriële afvalwater. Biosorpsie behels die gebruik van dooie biologiese materiaal om anorganiese of organiese besoedelingstowwe, of beide, te sekwestreer. Mikroalge het 'n verskeidenheid algespesies wat meestal in varswaterliggame voorkom, waarvan slegs 'n paar ondersoek is vir hul biosorpsiepotensiaal. Hierdie studie het gefokus op die gebruik van groen alge-sorbente vir die herwinning van seldsame aardelemente (REE) en die verwydering van swaar metale. Die algemonsters is versamel by die Hartbeespoortdam in Suid-Afrika en geïsoleer met behulp van die streepplateringsmetode. Die suiwer algespesies is geïdentifiseer met behulp van molekulêre metodes en daar is bevind dat hulle 95%-98% identiteite met Chloroidium saccharophilum, Desmodesmus multivariabilis, Scenedesmus acuminutus en Stichococcus bacillaris het. Chlorella vulgaris en Chlamydomonas reinhardtii is vir vergelykingsdoeleindes aangekoop. Die spesies is onder beheerde toestande in die laboratorium gekweek en gedroog om dooie algeselle vir biosorpsiestudies te verkry. Adsorpsie- en desorpsie-eksperimente is uitgevoer om die sorpsiekapasiteit en moontlike herwinning in enkelmetaalstudies van lantaan (La), tallium (Tl) en kadmium (Cd) te bepaal. Kinetiese studies is ook ondersoek om die potensiële tempobeheerstappe te bepaal wat nuttig is wanneer 'n volskaalse biosorpsieproses ontwerp word. Oppervlakkarakterisering van alge is uitgevoer om die moontlike meganismes betrokke by biosorpsieprosesse te bepaal. Multimetaalstudies is ondersoek om die invloed van mededingende ione in die werklike omgewing beter te verstaan.

IsiZulu: I-Biosorption ubuchwepheshe obusafufusa noma obuhambisanayo ezindleleni ezijwayelekile zokwelashwa kwamanzi angcolile ezimbonini. I-Biosorption ibandakanya ukusetshenziswa kwezinto eziphilayo ezifile ukuze kuthathwe izinto ezingaphili kanye nezinto ezingcolisa imvelo. I-Agae encane lunezinhlobonhlobo zohlobo lwe-algal ezitholakala kakhulu emanzini ahlanzekile futhi ezimbalwa zazo kuphela eseziphenywe amandla azo e-biosorption. Lolu cwaningo lugxile ekusetshenzisweni kwama-algal sorbent aluhlaza ukuze kutholakale izakhi zomhlaba ezingavamile (i-REE) kanye nokususwa kwezinsimbi ezisindayo. Amasampula e-algal aqoqwa edamini lase-Hartbeespoort eNingizimu Afrika futhi ahlukaniswa kusetshenziswa indlela yokucwenga (i-streak plating). Izinhlobo ze-algal ezihlanzekile zihlonzwe kusetshenziswa izindlela eziphathelene namamolekhuli futhi kwatholakala ukuthi zinezimpawu ezingama-95-98% ku -Chloroid saccharophilum , i-Desmodesmus multivariabilis, i-Scenedesmus acuminutus kanye ne-Stichococcus bacillaris . I-Chlorella vulgaris ne-Chlamydomonas reinhardtii zathengwa ngezinjongo zokuqhathanisa. Lezi zinhlobo zakhuliswa elabhorethri ngaphansi kwezimo ezilawulwayo futhi zomiswa ukuze kutholwe amaseli afile e-algal ukuze kwenziwe izifundo ze-biosorption. Ukuhlolwa kwe-Adsorption kanye ne-desorption kwenziwa ukuze kutholwe umthamo we-sorption kanye nokululama okungenzeka ocwaningweni olulodwa lwensimbi ye-lanthanum (i-La), i-thallium (i-Tl) ne-cadmium (Cd). Izingcwaningo ze-kinetic ziphinde zaphenywa ukuze kutholwe izinyathelo zokulawula izinga okungenzeka zibe usizo lapho kuklanywa inqubo ye-biosorption yesilinganiso esiphelele. Ukuphawula kwezinhlamvu ezingaphezulu ze-algae kwenziwa ukuze kunqunywe izindlela ezingenzeka ezibandakanyekayo kuzinqubo ze-biosorption. Ucwaningo oluphathelene nezinsimbi eziningi lwaphenywa ukuze kuqondwe kangcono umthelela wama-ayoni aqhudelanayo endaweni yangempela.