Investıgatıon Of Nıckel Recovery By Bıogranules Taılored For Metal Recovery Through Bıomıneralızatıon

Abstract

Electronic waste production in the world is increasing day by day. Nowadays, PCBs, which are one of the most important components of electronic waste, are considered as more valuable metal resources than ores due to their high value- and base-metal contents. Commercial metal recovery applications from WPCBs are mostly carried out using chemical techniques. However, due to the high chemical and energy consumption of these chemical techniques, development of alternative biological recovery techniques is essential to minimize the environmental impact of recovery processes.

In this thesis study, it is aimed to use biogranules that are capable of denitrification and urea hydrolysis for selective metal recovery from bioleachate solutions obtained via bioleaching of WPCBs. Selective nickel recovery performance of mature biogranules which were produced from seed sludge and exposed to incrementing nickel concentrations was investigated. Upon reaching steady conditions very compact and small granules with 0.2-0.6 mm size were obtained and the SVI30 values were recorded in the range of 7-9 mL/g. Produced biogranules could consume 55% and 100% of the urea and nitrate fed under anoxic conditions, respectively. Although the microbial performance of the granules increased by 39.8% as a result of nickel acclimation, deterioration in the granule structure and increase in flocs were observed.

Upon acclimation, metal recovery performance of biogranules were investigated in bioleachate solutions prepared with 1:20, 1:10, 1:5 and 1:2.5 dilution ratios. As a result of the process, the biomineralization process performed in 1:10 dilution ratio was determined as the most efficient concentration in terms of both microbial activity and recovered nickel purity (24.82%). In addition to nickel, zinc and copper could be effectively separated from the liquid and thus nickel purity decreased.