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Cilj rada bio je ispitati učinkovitost uklanjanja nitrata iz modelnih vodenih otopina adsorpcijom na kemijski modificirani pivski trop, lignocelulozni nusproizvod iz proizvodnje piva. Primjenjivost modificiranog pivskog tropa kao adsorbensa istražena je provođenjem šaržnih adsorpcijskih eksperimenata, pri čemu je istražen utjecaj masene koncentracije adsorbensa (1 - 8 g/L), vremena adsorpcije (1 – 1440 min), početne masene koncentracije nitrata (25 – 200 mg/L) te pH (2 - 12) na učinikovitost adsorpcije. Učinkovitost adsorpcije, odnosno postotak uklanjanja nitrata bio je veći od 60 % u svim provedenim eksperimentima (od 60 % do 100 %). Postotak uklanjanja povećavao se povećanjem masene koncentracije adsorbensa te produljenjem vremena kontakta između adsorbensa i adsorbata. Povećanje početne masene koncentracije nitrata dovelo je do smanjenja učinkovitosti procesa adsorpcije, dok pH nije imao značajan utjecaj na učinkovitost adsorpcije (osim u slučaju pH vrijednosti 12). Eksperimentalni podatci dobiveni provođenjem šaržnih adsorpcijskih eksperimenata analizirani su primjenom Freundlichova i Langmuirova ravnotežnog adsorpcijskog modela te je zaključeno kako oba modela dobro opisuju proces adsorpcije nitrata na modificirani pivski trop. Analiza podataka primjenom kinetičkih modela pokazala je kako navedeni proces adsorpcije dobro opisuje model pseudo-drugog reda te kako unutarčestična difuzija nije jedini korak koji ograničava proces difuzije. Kemijski modificirani pivski trop uspješno je primijenjen kao adsorbens za uklanjanje nitrata iz vodenih otopina. The aim of the study was to investigate the efficiency of adsorptive removal of nitrate from model aqueous solutions using chemically modified brewers' spent grain, a lignocellulosic by-product of beer production, as adsorbent. The applicability of the modified brewers' spent grain as adsorbent was evaluated in batch adsorption experiments, whereas the effect of different parameters on the adsorption efficiency was investigated. Namely, mass concentration of adsorbent (1 - 8 g/L), adsorption time (1 - 1440 min), initial mass concentration of nitrate (25 - 200 mg/L) and pH (2 - 12). The adsorption efficiency, i.e. the percentage of nitrate removal, was greater than 60% in all the experiments performed (60% to 100%). The percentage of nitrate removal was increased by increasing the mass concentration of the adsorbent and extending the contact time between the adsorbent and the adsorbate. An increase in the initial mass concentration of nitrate led to a decrease in the efficiency of the adsorption process, whereas pH had no significant effect on the adsorption efficiency (except in the case of pH value 12). The experimental data obtained from batch adsorption experiments were analysed using the Freundlich and Langmuir equilibrium adsorption models and it was concluded that both models well describe the nitrate adsorption process on the modified brewers' spent grain. Analysis of the data using kinetic models showed that the above adsorption process is well described by the pseudo-second order model and that intracellular diffusion is not the only step limiting the diffusion process. The chemically modified brewers' spent grain has been successfully used as an adsorbent for the removal of nitrates from aqueous solutions. |
