Adsorption of Heavy Metals from Small-Scale Gold Processing in Baguio Mining District, Philippines

Small-scale mining in the Philippines lacks research and technologies for the application of an inexpensive and environmentally sound treatment of its wastewaters. Hence, laboratory-scale fixed-bed column tests were carried out to test and evaluate the sorbent adsorption performance of the Philippine Natural Bentonite (PNB) and the Philippine Natural Zeolite (PNZ) against the heavy metals present in the ball mill facilities within the Baguio Mining District. Results showed that removal percentages of PNB and PNZ in terms of lead (Pb) concentrations are 50.43% and 26.90%, respectively. Moreover, the dynamic uptake capacity and maximum adsorption capacity values of PNB showed greater values than PNZ and the sorption models, Bohart-Adams, Wolborska, Thomas, and Yoon-Nelson models, displayed good fit for the breakthrough curves. Furthermore, varying the flow rate and bed height manifested that an increase in flow rate yields a lesser saturation time while the rise in bed height increases uptake capacity, saturation time, and removal percentage of the system. Regarding the cost efficiencies of the sorbents, the study revealed that PNB is more cost-efficient than PNZ since only 1.13 Philippine pesos of PNB is required to remove a gram of Pb compared to PNZ, which costs 3.5 pesos. Therefore, this research concluded that PNB could be a better sorbent of Pb in terms of removal percentage and cost-efficiency. The study recommends further regeneration studies for the reusability of the sorbents after exhaustion and hopes that this research will be a springboard for further environmental studies.