The recovery of valuable metals from waste printed circuit boards (WPCBs) is crucial in order to harness their economic resources, and prevents potential environmental contamination. However, selective extraction of Cu and Zn, and the co-extraction of other metals as impurities at ambient temperature using selected lixiviants such as HCl, H2SO4, HNO3, trifluoromethanesulfonic acid (TFMS), NaOH, and mixtures of NaCl and CuCl2 was studied. It is shown that the extraction efficiencies of all the metals increased with increases in lixiviant concentrations. High selectivity of Cu and Zn toward Fe were achieved in dilute H2SO4, HNO3, TFMS, and 0.5 M NaCl + 0.1 M CuCl2, and low dissolution of Pb (<5%) was observed in all H2SO4 lixiviants. Almost 100% Zn extraction using NaOH lixiviants without trace of other metals was achieved. Therefore, 0.5 M NaCl + 0.5 M CuCl2, 1.0 M HNO3, 0.5 M H2SO4, and 1.0 M TFMS showed high extraction selectivity toward Cu and Zn with low chemical consumption, and produced pregnant leach solution rich in Cu and Zn, as well as residue containing Fe, Ni, and other metals.
Abstract. The adsorption capacity of PKS which was used as an adsorbent in this study was boosted by acid thermoactivation. The nitrate sorption potential, point zero charge (PZC) and surface area of the PKS were enhanced by the acid thermoactivation process. The process of sorption of nitrate from solution was analyzed using five different isotherm models [Langmuir, Freundlich, Temkin, Harkins-Jura, and Halsey isotherm equations]. The value of the Langmuir monolayer sorption capacity qm [mg/g] increased from 60.12 to 85.73, PZC values increased from 5.50 to 8.40, and the surface area [m 2 /g] value increased from 29 m 2 /g to 98 m 2 /g after the activation process. The effect of pH on the sorption of the nitrate on both sorbents was also considered and it was discovered that the adsorption of nitrate decreases with increase in nitrate solution pH. The effects of the sorbents dose on the sorption process was also studied and the results showed that the amount of nitrate sorbed by both sorbent decreases with increase in sorbent dose.
The adsorption capacity of Palmkernel shell (PKS) which was used as an adsorbent in this study were boosted by acid thermoactivation. The nitrate sorption potential, point zero charge (PZC) and surface area of the PKS were enhanced by the acid thermoactivation process. The process of sorption of nitrate from solution was analyzed using five different isotherm models [Langmuir, Freundlich, Temkin, Harkins-Jura, and Halsey isotherm equations]. The value of the Langmuir monolayer sorption capacity qm [mg/g] increased from 60.12 to 85.73, PZC values increased from 5.50 to 8.40, and the surface area [m2/g] value increased from 29 m2/g to 98 m2/g after the activation process. The effect of pH on the sorption of the nitrate on both sorbents was also considered and it was discovered that the adsorption of nitrate decreases with increase in nitrate solution pH. The effects of the sorbents dose on the sorption process was also studied and the results showed that the amount of nitrate sorbed by both sorbent decreases with increase in sorbent dose.
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