Influence of NH4OH concentration in synthesis of bismuth oxide to physicochemical properties and photocatalytic activity in methyl orange degradation

Abstract

Synthesis of bismuth oxide was undertaken by precipitation method using NH4OH precipitating agent with various concentrations. The purpose of this study was to determine the effect of NH4OH concentration on the physicochemical characteristics and photocatalytic activity of bismuth oxides produced. Bismuth oxide synthesis was conducted by varying the concentration of NH4OH which was 1.5 M and 2.5 M. Synthesis was carried out through a reaction between HNO3 and Bi(NO3)3.5H2O then added NH4OH with various concentrations. The resulting precipitate was then filtered and dried in an oven at 110 °C for 24 hours. After that, the oven product was calcined at 600 °C for 1 hour. The XRD results showed that bismuth oxide produced from precipitating agents with a concentration of 1.5 M and 2.5 M resulted in the same crystal structure mixture, namely α-Bi2O3 and γ-Bi2O3. Then the results of DRS-UV showed that products synthesized using 1.5 and 2.5 M NH4OH have band gap of 2.65 eV and 2.67 eV, respectively. Bismuth oxides synthesized with NH4OH 1.5 M and 2.5M has degradation rate constants of methyl orange of 4.46 × 10−2 and 2.37 × 10−2 M−1 min−1 respectively with percent degradation for 120 minutes at 82.98% and 37.23%, consecutively.