Removal of manganese from aqueous solution by aeration, alkalinisation, coagulation/flocculation and ion exchange by batch process : bachelor thesis

Mangan i željezo nužno je ukloniti iz vode za ljudsku potrošnju jer dovode do promjene njenih organoleptičkih svojstava (metalan okus i miris, crvenosmeđa boja) te do pojave mutnoće. Takva voda se ne može upotrijebiti ni u industrijske svrhe jer uzrokuje različite probleme - boji proizvode (papir, tekstil), sužava profil cijevi (uslijed stvaranja želatinoznih taloga i biomase) što smanjuje učinkovitost grijača te koroziju koja može dovesti do puknuća tankova i pumpi. Zbog svega navedenog nužno je smanjiti koncentraciju mangana i željeza u vodi za ljudsku potrošnju do ispod maksimalno dopuštenih koncentracija (MDK) koje iznose 0,05 mg/L za mangan te 0,2 mg/L za željezo. U ovome radu ispitano je uklanjanje mangana iz vodene otopine koncentracije γ ≈ 20 mg/L postupcima aeracije, alkalinizacije, koagulacije/flokulacije uz filtraciju te ionske izmjene na prirodnom zeolitu šaržnim postupkom. Kombinacijom navedenih postupaka postignuto je uklanjanje mangana do ≈ 50% s zaostalom koncentracijom u otopini u rasponu od 5,02 do 9,78 mg/L. Za ispitane eksperimentalne uvjete najoptimalnije bi bilo provesti uklanjanje mangana kombinacijom aeracije u trajanju od 1 h uz alkalinizaciju vapnenim mlijekom te ionske izmjene u vremenu od 40 min uz S/L omjer 2,0-2,5/50. Za postizanje zaostale koncentracije mangana ispod MDK buduća istraživanja bi trebalo usmjeriti na aeraciju uz alkalinizaciju do pH ≥ 9,5, a potom na višestupanjsku ionsku izmjenu na prirodnom zeolitu šaržnim postupkom i/ili postupkom u koloni.Manganese and iron should be removed from water for human consumption as they lead to changes in its organoleptic properties (metallic taste and odour, red-brown colour) and appearance of turbidity. Such water cannot be used for industrial purposes as well, since it causes different problems - colored products (paper, textile), narrowed pipes profile (due to the formation of gelatinous precipitates and biomass) which reduces the efficiency of the heaters, as well as corrosion which can cause the rupture of tanks and pumps. Thus, it is necessary to decrease the concentration of manganese and iron in water for human consumption below the maximum permissible concentrations (MPC) which equals 0.05 mg/L for manganese and 0.2 mg/L for iron. In this paper the removal of manganese from an aqueous solution of concentration γ ≈ 20 mg/L has been investigated by aeration, alkalinisation, coagulation/flocculation followed by filtration, and ion exchange on the natural zeolite by batch process. By combination of these methods the removal of manganese up to ≈ 50% has been achieved with a residual concentration in the range from 5.02 to 9.78 mg/L. For the examined experimental conditions, it would be the most optimal to perform manganese removal by aeration for 1 hour and alkalinisation with lime followed by ion exchange for 40 minutes and S/L ratio of 2.0-2.5/50. In order to achieve the residual concentration below the MPC, future studies should be focused onto aeration with alkalinisation to pH ≥ 9.5 and then to a multistage ion exchange on the natural zeolite by batch and/or column method