Ultrasound-Enhanced Catalytic Ozonation Oxidation of Ammonia in Aqueous Solution

Abstract

Excessive ammonia is a common pollutant in the wastewater, which can cause eutrophication, poison aquatic life, reduce water quality and even threaten human health. Ammonia in aqueous solution was converted using various systems, i.e., ozonation (O3), ultrasound (US), catalyst (SrO-Al2O3), ultrasonic ozonation (US/O3), ultrasound-enhanced SrO-Al2O3 (SrO-Al2O3/US), SrO-Al2O3 ozonation (SrO-Al2O3/O3) and ultrasound-enhanced SrO-Al2O3 ozonation (SrO-Al2O3/US/O3) under the same experimental conditions. The results indicated that the combined SrO-Al2O3/US/O3 process achieved the highest NH4+ conversion rate due to the synergistic effect between US, SrO-Al2O3 and O3. Additionally, the effect of different operational parameters on ammonia oxidation in SrO-Al2O3/O3 and SrO-Al2O3/US/O3 systems was evaluated. It was found that the ammonia conversion increased with the increase of pH value in both systems. The NH3(aq) is oxidized by both O3 and ·OH at high pH, whereas the NH4+ oxidation is only carried out through ·OH at low pH. Compared with the SrO-Al2O3/O3 system, the ammonia conversion was significantly increased, the reaction time was shortened, and the consumption of catalyst dosage and ozone were reduced in the SrO-Al2O3/US/O3 system. Moreover, reasonable control of ultrasonic power and duty cycle can further improve the ammonia conversion rate. Under the optimal conditions, the ammonia conversion and gaseous nitrogen yield reached 83.2% and 51.8%, respectively. The presence of tert-butanol, CO32−, HCO3−, and SO42− inhibited the ammonia oxidation in the SrO-Al2O3/US/O3 system. During ammonia conversion, SrO-Al2O3 catalyst not only has a certain adsorption effect on NH4+ but accelerates the O3 decomposition to ·OH.

Active Treatment of Contaminants of Emerging Concern in Cold Mine Water Using Advanced Oxidation and Membrane-Related Processes: A Review

“…The use of O 3 microbubbles for NH 3 -N treatment in mine water has distinctive advantages, including the fast kinetics of the process, complete oxidation of several contaminants in mixing effluents, and no residual salinity creation in the treated water. Recently, the ultrasounds combined with ozonation and SrO-Al 2 O 3 as a catalyst showed to be promising for NH 3 -N treatment [108]. With a combination of ultrasounds at a frequency of 25 kHz vs. 270 W ultrasonic power and ozone, the NH 3 -N conversion and N 2 gas yield were 83.2% and 51.8%, respectively.…”

Novel Nano-Fe2O3-Co3O4 Modified Dolomite and Its Use as Highly Efficient Catalyst in the Ozonation of Ammonium Solution

“…Thus, Chen et al [8] have shown the N 2 selectivity of 44.8% over MgO-Co 3 O 4 catalyst in the catalytic ozonation of ammonium solution. Liu et al [7] have shown the conversion of 83.2% and gaseous nitrogen selectivity of 51.8% on SrO-Al 2 O 3 catalyst in the catalytic ozonation of ammonium solution. The mechanism of catalytic ozonation of NH 4 + solution is involved with the following process.…”

“…Liu et al demonstrated that the SrO-Al 2 O 3 composite was an effective catalyst for ultrasound-assisted ozonation of NH 4 + solution. NH 4 + conversion of 83.2% and gaseous nitrogen selectivity of 51.8% were achieved [7]. Chen et al 2018 reported the synthesis of MgO-Co 3 O 4 (molar ratio 8 : 2) and claimed that an ammonia nitrogen removal and gaseous nitrogen selectivity reached to the value of 85.2% and 44.8%, respectively [8].…”

“…Since NH 4 Cl was used as a NH 4 + source, Clin solution could participate in the NH 4 + oxidation. Clanions could react with O 3 to form ClOwhich oxidized NH 4 + ion to nitrogen [4,7]. To investigate the stability of the catalysts, we carry out three cycles of catalytic ozonation of NH 4 + solution over Fe 2 O 3 -Co 3 O 4 /dolomite, and the result is presented in Figure 8.…”

Combining ozone and ultrasound technology to remove S2− in Bayer liquor

“…The results shows that US can enhance the decomposition of O 3 and form a large number of •OH [24] . Liu et al has studied the oxidation of ammonia in different systems, and reported that less than 13 % of ammonium radical ion (NH 4 + ) is oxidized and the nitrate ion (NO 3 − ) yield is 11.2 % in the US/O 3 system, which are more than O 3 or US system [25] . Thus, the synergistic effect of US and O 3 makes up for the defects of ozone and extends the possibility of industrial application.…”