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"Penggunaan semikonduktor untuk mereduksi ion logam beracun dalam penanganan limbah merupakan teknik yang relatif baru, misalnya pada reduksi C(VI). Teknik ini didasarkan pada terbentuknya pasangan elektron dan hole apabila semikonduktor ini dikenai foton yang energinya lebih besar dari band gap energi semikonduktor. TiO2 merupakan semikonduktor yang banyak digunakan karena mempunyai sifat kimia yang sesuai untuk reaksi fotokatalisis, kestabilan yang tinggi dan relatif murah. Kinetika reaksi reduksi Cr(VI) ternyata sesuai dengan persamaan Langmuir-Hinselwood, dengan menggunakan metode kecepatan awal, maka konstanta dalam persamaan ini dapat diperoleh.Percobaan ini dilakukan dengan menggunakan reaktor bertingkat dengan suspensi yang mengalir, dimana kecepatan aliran dipertahankan 8 L/menit untuk menjaga TiO2 masih dalam bentuk suspensi. Konsentrasi katalis yang digunakan adalah 0,5 g/L. Sumber foton diperoleh dengan menggunakan sepuluh buah lampu UV masing-masing dengan daya 10 watt yang disusun secara seri. Pada interval waktu tertentu sampel diambil dianalisis, dimana sebelumnya dilakukan penyaringan dahulu untuk memisahkan partikel TiO2, selanjutnya rafinatnya dianalisis dengan 1,5 diphenyl carbazid. Pengaruh pH, penambahan ion ammonium dan intensitas sinar UV terhadap kecepatan reaksi kemudian dievaluasi. Kecepatan reduksi Cr(VI) semakin besar pada larutan yang semakin asam, penambahan ion amonium sebagai hole scavenger akan mempercepat reaksi dan pengurangan intensitas sinar UV akan memperlambat reaksi reduksi Cr(VI).

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Semiconductor photocatalytic reduction is a relatively new technique for the removal dissolved toxic metal ions in wastewater, such as Cr(VI). This tecnology is based on the reactive electrons and holes generated on the surface of a semiconductor when it is illuminated by light with energy greater than it's band gap energy. TiO2 is the most widely used photocatayst because of its favorable chemical property, high stability and low cost. Kinetic studies showed that Cr(VI) reduction under UV irradiation is according to Langmuir-Hinselwood equation, using the initial rate method the constans of this equation were evaluated.

The experiments were carried out in cascade photoreactor system with recirculation of the suspension, the flow rate was maintained on 8 liter per minute to keep TiO2 in suspension. The reduction in aqueous suspension of TiO2 (0,5gram per liter of solution) and irradiation by using ten series 10 watt blacklight lamp. At the regular time interval aliquots were withdrawn to analized, the aqueous sampel were filtered to remove TiO2 particles and subsequently analized by 1,5 diphenyl carbazide. We evaluated the effect of pH, the addition of ammonium ions as a "hole scavenger" and light intensity on the kinetic reaction. The reduction rates of Cr(VI) by photocatalytic–induced were significantly higher for more acidic solutions . The presence of ammonium ions might act as scavenger of holes and promoted the photocatalytic reduction of Cr(VI) by electron. On reducing light intensity would reduce the reduction rate of Cr(VI)."

"The land area and production of rubber on smallholder rubber plantations contribute to about 85% and 81% of national rubber production, respectively. Based on this, having technology to utilize vulcanized natural rubber latex (NRL) in a way that is simple, inexpensive, energy-saving, environmentally friendly, and according to the quality standards of the processing of NRL is important. The purpose of the current research is to design of a prototype photoreactor ultraviolet light-emitting diodes (UV-LEDs) for the vulcanization of NRL that is irradiated (VNRLI) to produce NRL-irradiated free carcinogens and protein allergens. The methodology used is the technological development of a prototype photoreactor with an UV-mercury irradiator that located in a vertical cylindrical glass column with the capacity of VNRLI about 249.2 tons/year. The development of technologies applied to increase the capacity of VNRLI by enlarging the area of thin NRL films to be irradiated with UV-A rays derived from UV-LED irradiators that are more energy-efficient, long-life, and environmentally friendly than UV-mercury irradiators. The results allowed for the design of a prototype photoreactor UV-LEDs to process feed NRL with the capacity VNRLI about 522 tons/year. The UV-LED photoreactor prototype design results show that the UV-LED photoreactor prototype is ready to test the VNRLI process function that can produce NRL- irradiated free carcinogen and protein allergens."

"ABSTRAKFotoreaktor silinder berputar skala pilot yang dibuat dapat digunakan untuk mengolah limbah fenol dengan kapasitas 3000 liter. Tiga buah drum berputar dengan diameter 55 cm dan panjang 95 cm masing-masing. Pada setiap drum terdapat katalis TiO2/ZAL yang berukuran 5-8 mm yang diaktivasi dengan menggunakan energi foton dari lampu UV dan merkuri yang terpasang pada setiap drum. Dari hasil penelitian ini, fotoreaktor silinder berputar ini mampu mendegradasi fenol hingga mencapai 98% dalam waktu 240 menit pada kecepatan berputar drum sebesar 15 rpm dengan volume limbah sebesar 550 liter yang membutuhkan katalis TiO2/ZAL sebanyak 10 kg. Keefektifitas katalis TiO2/ZAL mengalami penurunan setelah pemakaian pertama. Penurunan keefektifitas katalis dilihat dari kemampuan fotodegradasi fenol sebesar 12% pada waktu tinggal yang sama.

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AbstractPilot scale Rotating Drums photoreactor made for the treatment of phenol with the capacity of 3000 liter. Three rotating drums with the diameter of 55 cm and length of 95 cm each is used. On every drum, there is TiO2/ZAL catalyst attached with the size of 5-8 mm activated by the energy of photon form UV lamp and Mercury Lamp attached on every drum. From this experiment, photoreactor rotating drums can decrease the concentration of phenol until 98% in 240 minutes with the speed of rotating drums of 15 rpm and the volume of wastewater of 550 liter need 10 kg of TiO2/ZAL catalyst. The effectiveness of TiO2/ZAL catalyst decrease after the catalyst is used once. The effectiveness decrease can be seen from the degradation of phenol by 12% with the same retention time.;"