Tiro Tshukudu

The ultrasonic degradation of direct pink was investigated in this study. Parameters affecting ultrasonic degradation degree such as ultrasonic power, pH, bubbling gas and the presence of inorganic salts, were examined. The results showed that the addition of inorganic salts (NaCl, CuSO4) facilitated the degradation of direct pink while the addition of K2CO3 inhibited it. The degradation degree was enhanced significantly in the presence of saturated gases as listed here in decreasing order of effectiveness: argon > air > oxygen > nitrogen. The degradation degree of direct pink was largely influenced by pH value and boosted by acidic condition. The optimum degree could be achieved when pH value was 3.0 or when the sound power was 150 W. However, the degradability decreased notably in alkaline condition. Also, ultrasound/H2O2 technology was used, and the results showed that ultrasound/H2O2 has a better effect on the degradation than ultrasound alone or with H2O2 oxidation. Af...

Catalytic oxidation of malachite green using the microwave-Fenton process was investigated. 0% of malachite green de-colorization using the microwave process and 23.5% of malachite green de-colorization using the Fenton process were observed within 5 minutes. In contrast 95.4% of malachite green de-colorization using the microwave-Fenton was observed in 5 minutes. During the microwave-Fenton process, the optimum operating conditions for malachite green de-colorization were found to be 3.40 of initial pH, 0.08 mmol/L of Fe2 +  concentration and 12.5 mmol/L of H2O2 concentration. Confirmatory tests were carried out under the optimum conditions and the COD removal rate of 82.0% and the de-colorization rate of 99.0% were observed in 5 minutes. The apparent kinetics equation of −dC/dt = 0.0337 [malachite green]0.9860[Fe2 + ]0.8234[H2O2]0.1663 for malachite green de-colorization was calculated, which implied that malachite green was the dominant factor in determining the removal efficienc...

In this paper, results of an experimental study of polymeric phosphate-aluminum chloride (PPAC) as a modified coagulation reagent used to treat wastewater and fractal characteristics of flocs in a sewage treatment process were presented. Operating variables such as P/Al molar ratio, wastewater initial pH, coagulant dosage and agitation speed, which could influence the coagulation behavior of PPAC were experimentally tested. The evaluation of treatment efficiency was determined by measuring both the reduction of chemical oxygen demand (COD) and residual turbidity. It showed that the optimum removal efficiency was achieved when the P/Al molar ratio, wastewater initial pH, coagulant dosage and agitation speed were 1.2, 9.0, 0.36g/L and 100rpm respectively. Under optimum conditions, the removal efficiency was 73.5% and 99.5% for COD and turbidity. In addition, radial basis function (RBF) neural network established in this paper was used to predict the flocculation efficiency. The results revealed a promising operational forecasting capability. Furthermore, an inverted optical microscope was used to investigate the fractal structure of flocs formed during coagulation–flocculation. The results showed that under optimum conditions, with the increase of fractal dimension of the flocs, the COD removal efficiency increased while the flocs became denser with large cutter size.

In this study, two composite coagulants, PFPD1, and PFPD2, were prepared and studied with the inorganic polymer coagulant PFS. A response surface design was used to investigate the effect that changes in the level of coagulant dose and coagulation pH have on residual turbidity and TOC. In addition, the optimum combinations of dose and pH, that yield the lowest residual turbidity and TOC, were determined. The results revealed that the optimum conditions for the three coagulants were a dosage of 204 mg/L and pH of 8.06 for PFS; a dosage of 179 mg/L and pH of 7.99 for PFPD1; and a dosage of 112 mg/L and pH of 7.65 for PFPD2. The models showed that for residual turbidity, the effectiveness of the coagulants in decreasing order was PFS>PFPD1 > PFPD2, while for residual TOC, the order was PFPD2 > PFPD1 > PFS. The verification experiments demonstrated that a RSM approach was appropriate for optimizing the coagulation-flocculation process.