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"Dalam penelitian ini limbah logam berat (Cr dan Pt) dan organik (fenol) diolah secara simultan dengan metode fotokatalitik yang relatif masih baru, kemudian dilanjutkan dengan recovery terhadap logam berat Cr dan Pt. Percobaan fotokatalisis dilakukan meggunakan katalis berbasis TiO2 dalam fotoreaktor batch. Recovery logam Cr dan Pt masingmasing dilakukan dengan metode presipitasi dan leaching. Hasil penelitian menunjukkan adanya efek sinergisme antara reduksi logam berat (Cr6+ atau Pt4+) dan oksidasi senyawa organik (fenol) pada sistem fotokatalitik, yaitu dapat meningkatkan konversi masing-masing. Penambahan dopan ZnO (loading optimal = 0,5% berat) dapat meningkatkan kinerja fotokatalis TiO2 dalam mereduksi Cr(VI), meskipun tidak terlalu signifikan. Loading CdS (pada TiO2) yang optimal adalah sebesar 1% berat, memberikan aktivitas tertinggi dengan konversi reduksi Cr(VI) dan oksidasi fenol masing-masing ≥ 97 % dan 93 %. Reduksi Platinum menggunakan fotokatalis 0,5%ZnO-TiO2 dan 1%CdS-TiO2 terbukti cukup efektif dengan konversi > 99 % selama 2 jam reaksi. Proses recovery Cr(III) mencapai hasil optimal pada pH = 9, dengan efisiensi recovery sebesar 91 %. Suhu leaching optimal pada proses recovery Pt adalah 100 oC, dengan efisiensi recovery sebesar 86 %.

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Simultaneous Treatment of Organic (Phenol) and Heavy Metal (Cr6+ or Pt4+) Wastes over TiO2, ZnO-TiO2 and CdS-TiO2 Photocatalysts. Treatment of heavy metal (Cr6+ and Pt4+) and organic (phenol) wastes has been studied using the relatively new method, i.e. simultaneous photocatalytic process over TiO2 photocatalysts in the batch photoreactor. Following the photocatalytic reduction of the heavy metal wastes, recovery of Cr and Pt was carried out by precipitation and leaching method, respectively. The experimental results show that in the simultaneous photocatalytic system, there is a synergism effect between the photocatalytic reduction of heavy metal waste (Cr6+ or Pt4+) and the oxidation of organic waste (phenol), so that increasing the conversion of each other. Dopant of ZnO with the optimum loading (0.5 wt%) could slightly increase the performance of TiO2 photocatalyst in photocatalytic treatment of the wastes. Whereas CdS dopant with the optimum loading of 1 wt% could significantly enhance the performance of TiO2 photocatalyst in simultaneous Cr(VI) reduction and phenol oxidation with the highest conversion of ≥ 97 % and 93 %, respectively. Photocatalytic reduction of Pt(IV) under 0.5%ZnO-TiO2 and 1%CdS-TiO2 photocatalysts effectively occurred with a high conversion (> 99 %) in 2 hours irradiation of UV. The optimum precipitation condition of Cr(III) recovery was achieved at pH = 9, with the efficiency of recovery was 91 %. Optimum temperature of leaching process in Pt recovery was 100 oC, with the efficiency of recovery was 86 %."

"This present study is aimed at removing phenol compounds in wastewater by using a Contact Glow Discharge Electrolysis (CGDE) reactor. To start with, the effect of voltage to direct current connections in a CGDE reactor was investigated in order to estimate several possibilities for optimum voltage for phenol degradation. Several parameters were studied for phenol treatment including the effects of voltage, electrolyte concentration, anode depth, and the presence of Fe2+ ions. Production of hydrogen peroxide, the percentage of phenol degradation, and energy consumption were used as main research indicators. The optimum condition was found at 700 V, in 0.03 M Na2SO4, and an anode depth of 5mm. The phenol degradation was valued at 40.83% after the first 15 minutes in the process, with an energy consumption of 278 kJ/mmol of phenol. Under the same conditions, with an addition of 20 mg/L of Fe2+ ions, the phenol degradation shot up to 92.57% and energy consumption significantly decreased to 127 kJ/mmol. The largest phenol degradation was obtained at 99.6% after 90 minutes during the experiment. The results pointed out a promising path for phenol treatment in wastewater by utilizing a CDGE reactor with recommended operating conditions which were obtained during this study."