Technological viability of coffee husk ash, soil rich in koalinite-ferrinatrite and koalinite-geothite for the adsorptive removal of chromium (VI) from industrial wastewater = Ukusebenziseka kobuchwepheshe bomlotha wekhofi i-husk, inhlabathi enothile ngeKaolinite-Firrinatrite kanye neKaolinite-Geothite ekukhucululeni okusansimbi okuphuma emanzinimfucuza yasezimbonini.

Doctor of Philosophy in Agricultural Engineering. University of KwaZulu-Natal, Pietermaritzburg 2017.

ABSTRACT: Most industries in developing countries discharge a high amount of untreated wastewater, containing toxic chemicals, into nearby water bodies. Heavy metals and chemicals above permissible levels can be emitted to the environment as wastewater effluents from industries such as leather, electroplating, tanning, metal, fertilizer, and other industries. When these are discharged into the environment, they significantly pollute the quality of the water bodies and the environment, thereby substantially affecting river and human health. The safe and effective purification of polluted water containing heavy metals is always a challenge in many parts of the world, because cost-effective treatments are not readily available. Various methods are used for removing heavy metals, such as irradiation, chemical precipitation, ion exchange, adsorption, biological and chemical treatment. However, the adsorption technique is the best option due to easy to operate, simple, cheap, efficient, and suitable for the environment. The adsorption method is a suitable technique for developing countries like Ethiopia, where the advanced wastewater treatment technologies for high amount of toxic industrial wastewater are unaffordable. Locally-available adsorbent materials reasonably meet the criteria that have been established for the wastewater treatment process, due to their natural availability as adsorbents, their high natural porosity, their very low price, easy design, operation and maintenance, as well as their suitability for pollutant adsorption. The applicability of low-cost, locally-available adsorbent materials for the adsorptive removal of heavy metals from industrial wastewater is important. This study investigated the technological viability of low-cost materials, such as coffee husk ash, soil that is rich in kaolinite (40.4%) and ferrinatrite (59.6%), and soil that is rich in kaolinite (29.4%) and goethite (70.6%), for the adsorptive removal of chromium from industrial wastewater. The physical properties and elemental composition of the three adsorbents (soil rich in kaolinite-ferrinatrite, coffee husk ash and kaolinite-geothite) were characterized. The experiments were conducted under batch adsorption set-ups to assess the effect of different parameters and their optimum removal efficiency. The optimum adsorption of Cr(VI) on the three adsorbents used were observed at 40 minutes and two pH values and their doses of adsorbent, shaker speed, and initial Cr (VI) ion concentration were different in the batch adsorption experiments. The adsorption of Cr(VI) followed pseudo second-order kinetics, with a coefficient of determination r2 > 0.99 for the three-adsorbent media. Results of the adsorption isotherm show that Freundlich adsorption isotherm model better described Cr(VI) adsorption into soil rich in kaolinite-ferrinatrite (SRKF), soil rich in kaolinite-geothite (SRKG) and coffee husk ash (CHA) with coefficients of determination; r2 > 0.93. The adsorption capacity of the adsorbent followed the decreasing order CHA >SRKF > SRKG. The findings on the adsorption characteristics of batch system from this work suggests that soil rich in kaolinite-ferrinatrite, coffee husk ash and soil rich in kaolinite-goethite could represent an interesting low-cost naturally available adsorbent material that could be used for the chromium (VI) removal from wastewater. The empirical data and models developed in the study were used to establish theoretical design analysis of adsorptive treatment plant for industry emits such wastewater. However, further investigations will be required for the practical application of these locally-available adsorbent materials for the removal of chromium from wastewater. IQOQA LOCWANINGO:Izimboni eziningi emazweni asathuthuka zikhipha amanzimfucuza amaningi achithwa engahlanzwanga, anamakhemikhali nobuthi, ezindaweni zokuchitha amanzi. Imfucuzamanzi yesikhumba, i-electroplating, i-tanning, okusansimbi, isivundisi, nobunye ubuxhamaxhama, bunamakhemikhali kanye nokusansimbi okunobungozi obungaphezu kwezinga elivunyelwe. Uma konke lokhu sekuchithwe emphakathini, kungcolisa kakhulu izindawo zokuchitha amanzi kanye nendawo, ngaleyo ndlela kuphazamisa impilo yamanzi kanye nempilo yabantu. Indlela ephephile nesebenzayo yokuhlanza amanzi angcolile anokusansimbi okusindayo kuhlale kunezinqinamba ezindaweni eziningi emhlabeni, ukuhlanzwa okungabizi kakhulu akutholakali kalula. Izindlela ezahlukahlukene zisetshenzisiwe ukukhipha okusansimbi okusindayo, njenge- irradiation, ukusefa amakhemikhali, ukushintsha inhlasigesi, i-adsorption, ukuhlanzwa kwamakhemikhali nokuphilayo. Kodwa-ke isu le-adsorption yilona elidla ubhedu ngenxa yokuthi lenzeka kalula, lisobala, alibizi, lisebenza kahle, futhi liyifanele indawo. Uma sibheka uhlaziyo olungenhla, indlela ye-adsorption yilona lisu elifanele lamazwe asathuthuka afana ne-Ethiopia, lapho ubuchwepheshe obusezingeni eliphezulu bokuhlanza amanzi ebuthini obuningi obusuka emfucuzeni yamanzi asezimbonini lungakwazi ukuthi lwenzeke. Amathuluzi okusebenza ekhaya akhona e-adsorbent ahambisana kahle nezimo zokwenza ezakhiwe uhlelo lokwelapha amanzimfucuza ngenxa yokubakhona kwama-adsorbents ngokwemvelo, ukuba khona kwezimbotshana kwalo ngokwemvelo, amanani aphansi, umumo olula, ukusebenziseka kanye nokugcineka kwalo, nokulungela kwalo i-adsorption engcolisekile. Ukuba khona kwamanani aphansi, amathuluzi akhona e-adsorbent ekhaya okususa okusansimbi okusindayo kwe-adsorptive kumfucuzamanzi yasezimbonini kubalulekile. Lolu cwaningo luhlole ukuthi amathuluzi enani eliphansi obuchwepheshe angasebenza yini, njengomlotha wekhofi i-husk, inhlabathi enothile ku-kaolinite (ama-40.4%) ne-ferrinatrite (ama-59.6%), kanjalo nenhlabathi enothile ku-kaolinite (ama-29.4%) ne-goethite (70.6%), yokususa i-adsorptive ye-chromium kumfucuzamanzi yasezimbonini. Amalinge enziwa ngaphansi kwe-batch ye-adsorption eyenzelwe ukuhlola umthelela wamapharamitha ahlukahlukene kanye nokusuka kwawo ngokuphelele. I-adsorption ephelele yenhlabathi enothe nge-kaolinite-ferrinatrite, umlotha wekhofi i-husk kanye ne- kaolinite-goethite yabonwa ngokujwayelekile emizuzwini engama-40 kanye namaveluzi amabili e-pH kanye namadosi e-adsorbent, ijubane le-shaker, kubandakanya i-Cr yokuqala (VI) ubukhona be-ion babuhlukile kuma-batch amalinge e-adsorption . I-adsorption Cr(VI) ilandele i-pseudo second-order kinetics, inokudlelana ne-coefficient engama-R2 > 0.99 ngama-adsorbent amathathu ezokukhangisa. Imiphumela ye-adsorption isotherm ikhombisa ukuthi imodeli ye-Langmuir adsorption isotherm echazwa kahle njenge-Cr (VI) adsorption enhlabathini enothe nge-kaolinite–ferrinatrite (i-SRKF), inhlabathi enone nge-kaolinite–geothite (SRKG) kanye nomlotha wekhofi i-husk (i-CHA) nobudlelwano obuyi-coefficient; ama-R2 > 0.93. Umthamo we-adsorption ye-adsorbent kungahlelwa ngendlela eyehlayo i-CHA >SRKF > SRKG. Okutholakele emisebenzini ye-adsorption yezinhlelo zama-batch kulo msebenzi kuphakamisa ukuthi inhlabathi enothile ku-kaolinite-ferrinatrite, umlotha wekhofi i-husk kanye nenhlabathi enothe ku-kaolinite-goethite ingamelela izinto ezitholakala ngenani eliphansi ngokwemvelo ze- adsorbent ezingasetshenziselwa i-chromium (VI) ukususwa kumanzimfucuza. Ulwazi oluhloliwe locwaningo kanye namamodeli akhiwe ocwaningweni asetshenziswe ukwakha umumo wokuhlaziya wenjulalwazi yomshini wokwelapha i-adsorptive embonini eqokiwe. Yize kunjalo, kusadingeka ukuthi kwenziwe ucwaningo oluzoveza ukusebenza-ke manje kwale-adsorbent etholakala ekhaya esusa i-chromium kumanzimfucuza.