Optimasi dosis flokulan pada sirkuit gold pre-leach thickening serta pengaruhnya terhadap proses carbon-in-leach di PT. Antam tbk UBPE Pongkor Jawa Barat = Optimization of flocculant dosage on gold pre-leach thickening circuit and its effect for carbon-in-leach process at PT. Antam tbk UBPE Pongkor West Java