Bulk balance filtration model (BBFM) for lead and iron physisorption through Moringa oleifera Lam. seed husks

It is well known that Moringa oleifera Lam. (MO) seeds, pods and leaves have coagulant-flocculant and adsorptive properties, and it is a worth candidate for water treatment that can partially substitute commonly used adsorbents such as granular activated carbon, sand and zeolite. Lead (Pb) and iron (Fe) adsorption using borosilicate columns packed with MO seed husks for water purification purposes was investigated. A model (Bulk Balance Filtration - BBFM or Bulk Model for short) for contaminant adsorption was derived and applied to iron and lead data. The BBFM parameters found were: c=1.324 cm², n = 0.5949 and λ_o = 0.1251 cm^-1; and c = 2.232 cm², n = 0.9792 and λ_o = 0.1027 cm^-1 for iron and lead, respectively. The Bulk Model is useful for scaling-up purposes and correlated better than classic models such as the BDST, Thomas, and the Yoon-Nelson under specific conditions. Results from batch and continuous processes suggest that Fe and Pb removal mechanism with MO husk corresponds to that of a physisorption process.