Utilization of Mt. Pinatubo lahar/pyroclastic materials for mineral oxides production; 1: extraction of alumina; 2: extraction of silica; 3: extraction of ferric oxide

Aluminum oxide or alumina was extracted from lahar using 10, 20, 30, and 40 g of NaOH as extractant using a modified Bayer process. The time of digestion was varied to 1, 2, 4, and 5 hrs. The pH precipitation was also varied by adding different amounts of HCl to produce solutions with pH ranges 11.00 to 8.51, 8.50 to 6.51, and 6.50 to 0.01. The effects of the treatment conditions on yield of alumina from lahar analyzing 18.4 percent were determined. The yield of alumina ranges from 3.31 percent, using 10 g of NaOH at 1 hr of digestion, with a pH range of precipitation of 0.01-6.5, to 95.83 percent, using 40 g of NaOH at 5 hrs. of digestion, with a pH range of precipitation of 8.51 to 11.00. The amount of NaOH used, time of digestion and pH of precipitation were found to have significant effects on the yield of alumina. Increasing the amount of NaOH, time of digestion and pH of precipitation increases the alumina yield. The best operating conditions were found at 40 g of NaOH, 5 hrs of digestion time and pH of precipitation of 8.51 to 11. Silicon dioxide or silica was extracted from the pyroclastic materials of Mt. Pinatubo with an extraction method using a Na2CO3 and K2CO3 fusion mixture, HCl and gelatin. Different sample: fusion mixture ratios (1:1, 1:3, and 1:5) were tested at different pH ranges (0.1-2.4, 2.4-4.4, and 4.5-7.0) to determine their effects on the purity and recovery of silica. The silica content of lahar used and extraction products was determined gravimetrically. The feed material and extraction products contain 52.4 and 76.2 to 86 percent silica, respectively. The recovery after extraction ranged from 48.34 percent using a 1:1 sample: fusion mixture ratio to 68.28 percent at a ratio of 1:3 both treated at a pH range of 0.1 to 2.4. The amount of HCl added and sample: fusion mixture ratio were found to have a significant effect on the purity and recovery of silica. The condition that would give a product of high purity and recovery was found to be at a pH range of 0.1 to 2.4 using a sample: fusion mixture ratio of 1:3. Ferric oxide was extracted from Mt. Pinatubo with an extraction method using HCl as the extracting solvent and NH4OH as precipitant. Different samples were treated under three conditions: time of digestion (1, 2, 3, 4, 5, 6 hrs), amount of extracting solvent (20, 30, 40, 50, 60 mL) and pH of precipitation (9.34, 9.61, 10.04, 10.57) to determine their effect on the percent recovery and purity of extracted ferric oxide from lahar. The ferric oxide content of the Mt. Pinatubo lahar was determined gravimetrically. The sample was found to have 4.6 percent ferric oxide and the purity of the extracted crude ferric oxide was found at a range of 35.3 percent to 37.9 percent. The average percent recovery of ferric oxide ranged from 23.647 using 20 mL at pH 1.4 digested for 1 hr to 77.118 using 60 mL at pH 0.75 and digested for 3 hrs. Using statistical analysis, the three factors tested in this study were found to have significant effects on the percent recovery and purity of ferric oxide