Photocatalytic Hydrogen Production from Urine Using Sr-Doped TiO2 Photocatalyst with Subsequent Phosphorus Recovery via Struvite Crystallization

Currently, the discharge of wastewater and utilization of phosphorus (P) in human activities cause some environmental problems, such as high organic pollutants in aquatic environments which results in dirty water sources, and a shortage of phosphate rock reserves due to the high demand of P. Therefore, fuel energy and struvite crystallization from waste sources can be considered interesting alternatives. In this work, the modified catalyst for hydrogen production, along with solving environmental problems, was examined. The strontium (Sr) doped-titanium dioxide (TiO2) nanoparticles were synthesized by wetness impregnation method. The synthesized catalyst was characterized using UV-vis spectroscopy (UV-vis), photoluminescence (PL), X-ray diffraction (XRD), photoluminescence (PL), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). The Sr-doped TiO2 catalysts had been utilized as the photocatalyst for the hydrogen production from synthetic human urine (a representative of waste source). The doping content of Sr in TiO2 varied from 0.5, 1, 2, and 4%, and the photocatalytic performances were compared with pristine TiO2 nanoparticles. The results showed that 1% Sr-doped TiO2 had the highest photocatalytic activity for hydrogen production and decreased the amount of chemical oxygen demand (COD) in the synthetic human urine. Subsequently, P could be recovered from the treated human urine in the form of struvite.

Struvite Crystallization for Ammonium Removal from Cow Urine with Bulkhead Reactor

Kandungan amonium dalam limbah urine sapi dapat merusak ekosistem perairan karena toksisitasnya. Kandungan amonium dapat dikurangi dengan menghilangkannya melalui kristalisasi struvite. Pada penelitian ini, struvite (MgNH4PO4.6H2O) terbentuk dari reaksi senyawa magnesium, amonium, dan fosfat yang dijalankan menggunakan reaktor kolom bersekat. Laju udara menggerakkan larutan di dalam reaktor menyebabkan amonium bereaksi dengan reaktan membentuk struvite. Penelitian ini dilakukan untuk mendapatkan kondisi penurunan amonium terbaik pada limbah urine sapi. Penelitian berjalan dengan perbandingan molar larutan M: A: P (magnesium amonium fosfat) 3: 1: 1 dan laju aliran udara 0,4 L / menit dengan variasi laju aliran MAP 8,8; 11; 14,67; 22; 44 ml / menit dan variasi suhu 25, 35, 45, 55, 65˚C untuk menurunkan kandungan amonium. Semakin cepat laju aliran MAP, semakin rendah efisiensi penurunan amonium. Efisiensi penurunan amonium akan meningkat dengan meningkatnya suhu. Hasil terbaik yang diperoleh dalam penelitian ini adalah penurunan amonium pada limbah sebesar 77,97%. Hasil difraksi serbuk sinar-X (XRD) dan scanning electron microscope (SEM) adalah kristal yang diuji berupa struvite berbentuk batang atau memanjang. Analisis EDAX memberikan hasil persentase komponen pada struvite yaitu 14,28% Mg, 10,68% N, dan 18,19% P.The presence of ammonium content in cow urine waste damages the aquatic ecosystem due to its toxicity. Ammonium content can be reduced by removing it through struvite crystallization. In this study, struvite (MgNH4PO4.6H2O) was formed from the reaction of magnesium, ammonium, and phosphate compounds using a bulkhead reactor. The rate of air moving the solution in the reactor causes ammonium to react with reactants to form struvite. This research was conducted with M : A : P (magnesium ammonium phosphate) molar ratio solution is 3 : 1 : 1 and 0,4 L/min air flow rate with MAP flow rate variation of 8,8; 11; 14,67; 22; 44 ml/min and a temperature variation of 25, 35, 45, 55, 65˚C to decrease ammonium content. The faster the MAP flow rate, the lower the ammonium removal efficiency. The efficiency of ammonium removal will increase with increasing temperature. The best results obtained in this study were ammonium removal in the waste of 77.97%. The result of x-ray powder diffraction (XRD) and scanning electron microscope (SEM) is the crystals tested was a struvite with elongated or rod shape. EDAX analysis gave the percentage of components in struvite, namely 14.28% Mg, 10.68% N, and 18.19% P.