Sains Malaysiana 45(3)(2016): 477–487

Photocatalytic Degradation of Some Charges Aqueous Phase Pollutants using Nafion and Silica Modified TiO₂

(Kemusnahan Fotomangkinan Beberapa Pencemar Tercas Fasa Akueus menggunakan TiO₂ Terubahsuai Nafion dan Silika)

CHOWDHURY, M.M.I. & VOHRA, M.S.*

Department of Civil and Environmental Engineering, King Fahd University of Petroleum and Minerals, Dhahran, Kingdom of Saudi Arabia 31261

Received: 25 December 2014/Accepted: 26 August 2015

ABSTRACT

The present study investigated the use of modified titanium dioxide (TiO₂) based photocatalytic degradation (PCD) process for the removal of some critical charged aqueous phase pollutants. First of all, the use of Nafion TiO₂ (Nf-TiO₂) and silica TiO₂ (Si-TiO₂) for the removal of aqueous phase ammonia (NH₄₊/NH₃) species employing near UV lamp as energy source was studied. The use of Nf-TiO₂ enhanced NH₄₊/NH₃ PCD with optimum removal noted for 1 mL of Nafion solution coating per g of TiO₂ and respective overall NH₄₊/NH₃ removal was about 1.7 times higher compared to plain TiO₂ at 6 h reaction time. Similarly the 0.5 mL silica solution coating per g TiO₂ sample, also enhanced NH₄₊/NH₃ removal with optimum efficiency similar to Nf-TiO₂. The results from effect of ammonia concentration on to its PCD using Nf-TiO₂ indicated that overall mass based NH₄₊/NH₃ removal was higher at greater NH4+/NH3 amounts indicating high efficiency of Nf-TiO₂. Similar trends were noted for Si-TiO₂ as well. Furthermore, the results from modified TiO₂ and mixed NH₄₊/NH₃ and cyanide (CN-) systems indicated successful removal of co-pollutant CN- along with simultaneous degradation of NH₄₊/NH₃ species at rates that were still higher than plain TiO₂. Nevertheless application of Nf-TiO₂ for the treatment of cationic dye methylene blue (MB) indicated slower MB removal compared to plain TiO₂ though significant MB degradation using Nf-TiO₂ could still be achieved at pH₃. Additionally the results from solar radiation energized PCD process indicated positive role of solar radiation for the removal of NH₄₊/NH₃ species under a varying set of conditions.

Keywords: Cationic pollutants; Nafion TiO₂; photocatalysis; solar energy; silica TiO₂

ABSTRAK

Penyelidikan ini mengkaji tentang penggunaan titanium dioksida terubah suai (TiO₂) berasaskan proses pemusnahan fotomangkinan (PCD) untuk sesetengah bahan pencemar tercas fasa akueus kritikal. Pertama ialah penggunaan semua TiO₂ Nafion (Nf-TiO₂) dan TiO₂ silika (Si-TiO₂) untuk penyingkiran ammonia fasa akueus spesies (NH₄₊/NH₃) yang menggunakan lampu dekat UV sebagai sumber tenaga telah dikaji. Penggunaan Nf-TiO₂ mempertingkatkan NH₄₊/NH₃ PCD dengan penyingkiran optimum bagi 1 mL salutan penyelesaian Nafion untuk setiap g TiO₂ dan keseluruhan penyingkiran NH₄₊/NH₃ adalah 1.7 kali lebih tinggi berbanding dengan TiO₂ plain pada masa tindak balas 6 jam. Lapisan larutan silika 0.5 mL untuk setiap g sampel TiO₂, juga mempertingkatkan penyingkiran NH₄₊/NH₃ dengan kecekapan optimum menyerupai Nf-TiO₂. Hasil daripada kesan kepekatan ammonia kepada PCD dengan menggunakan Nf-TiO₂ menunjukkan bahawa jisim keseluruhan berasaskan penyingkiran NH₄₊/NH₃ adalah lebih tinggi daripada jumlah NH₄₊/NH₃ yang menunjukkan kecekapan tinggi Nf-TiO₂. Trend serupa dilihat pada Si-TiO₂. Selain itu, hasil daripada TiO₂ diubah suai dan campuran NH₄₊/NH₃ dan sistem sianida (CN-) menunjukkan penyingkiran berjaya bersama pencemar CN- bersama-sama dengan kemerosotan serentak spesies NH₄₊/NH₃ pada kadar yang telah masih lebih tinggi daripada TiO₂ biasa. Walau bagaimanapun, aplikasi Nf-TiO₂ untuk rawatan kationik pencelup metilena biru (MB) menunjukkan penyingkiran MB lebih perlahan berbanding TiO₂ plain walaupun kemerosotan MB secara bererti menggunakan Nf-TiO₂ masih boleh dicapai pada pH₃. Tambahan pula keputusan daripada sinaran suria yang mengecas proses PCD menunjukkan peranan positif radiasi solar untuk penyingkiran spesies NH₄₊/NH₃ di bawah satu set keadaan yang berbeza.

Kata kunci: Bahan pencemar kationik; fotomangkinan; tenaga solar; TiO₂ Nafion; TiO₂ silika

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*Corresponding author; email: vohra@kfupm.edu.sa