TECHNICAL PAPERON

“Recent Trends in Chemical Engg.”( Sonophotocatalytic Degradation of Waste Water )

PRESENTED BY

Mr. Tejas D. Deshpande

B.E. (Chemical)

TATYASAHEB KORE INSTITUTE OF ENGG. AND TECHNOLOGY, WARANANAGAR.

Generators of Waste WaterDomestic Wastewater

Bathing Washing Clothes, Utensils, Vehicles etc. Sanitation waste Landfill leachate Effluents Commercial

Industrial Waste Water Chemical Petroleum and Refining Food Processing Pharmaceutical Pulp and paper Textile Dye processing

Current Waste Water TreatmentsUnit operations and processes that have been employed to waste water

treatments are divided into 3 types according to various levels of treatment as :

1. Physical - Primary methods- Physical or Physio-chemical unit Operations e.g. filtration, adsorption, air flotation, flocculation and sedimentation

2. Biological - Secondary - Biological Operations. e.g. aerobic, anaerobic and activated sludge

3. Chemical – Tertiary- Advanced Processes evolving Chemical Change e.g. Thermal oxidation (Combustion), Chemical oxidation, Ion exchange, Chemical Precipitation

Drawbacks

Incomplete elimination of Toxic & Non-biodegradable organic pollutants

Need disposal of secondary waste materials generated in the process

Can Reduce BODs but Can not reduce CODs at desirable extent

Adsorption and Coagulation - NOT useful to treat harmful infectants present in the waste water

Sedimentation, filtration, Membrane technology - Expensive and Generate toxic secondary pollutants

Chlorination generates Mutagenic and Carcinogenic by-products

Need to test and set up the emerging alternative technologies to overcome the inconveniences of conventional treatment methods

Advanced Oxidation Processes: ( AOPs ) Groups of technologies that lead to hydroxyl radical (.OH) generation

.OH Radicals- Extremely unstable and reactive, High oxidation potential

Attack organic molecules & make New oxidized intermediates with lower molecular weight or in case of complete mineralization CO2 and water

AOP - Powerful and efficient treatment methods for degrading recalcitrant materials or mineralizing stable, inhibitory, or toxic contaminants

Increasingly gaining popularity - Potential of converting harmful organic pollutants into innocuous compounds such as CO2 and H2O

Fig. Mechanism of the oxidation of benzene by Hydroxyl Radicals

Types of AOPs AOPs based on Ozone

AOPs based on Hydrogen Peroxide

Fenton Oxidation process Photolysis Photo catalysis Sonolysis Sonochemical Sonoelectrochemical Electrochemical Sonophotocatalysis

Sonophotocatalysis (Sono + Photo + Catalyst)

Combination of two advanced oxidation processes i.e. Sonication and photo catalysis

Basic reaction mechanism for both Ultrasound initiated degradation and Photo catalytic oxidation- Generation of free radicals and subsequent attack by these on the pollutant organic species

In Photo catalytic oxidation, efficiency reduces due to blocking of the catalyst activated sites

Turbulence induced by Cavitation phenomena under the action of turbulence generated by acoustic streaming – Elimination the drawbacks associated with photo catalytic oxidation

More number of free radicals are generated due to combination of 2 modes ; thereby increases the rates of reaction

Reaction MechanismReactions involved in Photo catalysis:

TiO2 + hv → TiO2 (e- + h+) TiO2 (h+) + H2O → TiO2 + H+ + HO-TiO2 (h+) + OH- → TiO2 + HO• TiO2 (e-) + O2 → TiO2 + •O2H2O2 + hv → 2HO*

Reaction involved in Sonolysis:H2O + ))))→ H* + HO* H2O + ))))) → ½ H2 + ½ H2O2 H2O2 + H* → H2O + HO*

Instruments for Sonophotocatalysis pH meter

COD digester

Spectrophotometer

Ultrasonic bath or probe

UV source such as Lamp

Catalyst such as Zno,TiO2

Magnetic Stirrer

Magnetic Stirrer pH meter

UV Lamp

Parameters that must be looked upon pH = Acidic (2.5 - 5.5)

UV wavelength = 200 to 400 nm

US frequency = 20 kHz <

Type and Amount of catalyst = Zno,TiO2,etc.

Size of catalyst particles

Initial Concentration of waste water

Case StudySONOPHOTOCATALYTIC TREATMENT OF PHARMACEUTICAL

WASTEWATER( Department of Bio-Technology and Environmental Sciences, Thapar

University ,Patiala )Sr.No Parameter Prevailing Range

(mg/ml)

1 pH 3.75

2 COD 32

3 BOD 12.8

4 TS 25.2

5 TDS 23.9

6 TSS 1.3

7 Sulphate 3.716

8 Chloride 7.526

WASTE WATER CHARACTERISTICS

Sample taken = 1000 ml pH = 4.0 Catalyst = TiO2 Amount of TiO2 catalyst = 1 - 7 gm. Oxidant = H2O2 (works as promoter) Amount of Oxidant H2O2 = 2.3-30 ml Residence Time = 2 Hrs. Wavelength of UV lamp = 280 nm Frequency of Ultrasound = 42 KHz Size of TiO2 Catalyst = 47.1-67.5 nm.

Methodology

Sr.No

Parameter

Prevailing Range (mg/ml)

After Sonophotocatalytic Treatment (mg/ml)

Percentage Degradation

1 pH 3.75 7.1 -

2 COD 32 0.32 99%

3 BOD 12.8 0.15 98.8%

4 TS 25.2 0.00 100%

5 TDS 23.9 0.102 99.5%

6 TSS 1.3 0.00 100%

7 Sulphate 3.716 0.232 93.7%

8 Chloride 7.526 0.092 98.7%

Final Characteristics

Results show that-

Efficient and Environmental friendly technique

Almost 95% degradation of recalcitrant organic pollutants

Wastewater compounds are degraded rather than concentrated or transferred into a different phase - No need of disposal of any materials

Increases the chances for the reuse of wastewater

So, we can say that Sonophotocatalysis has a good capability to treat the waste water of various industries

Results & Discussions

Advantages More number of free radicals will be available for the reaction thereby

increasing the rates of reaction

Rate constants of the combined process are greater than the sum of the rate constants of the individual processes

Wastewater compounds are degraded rather than concentrated or transferred into a different phase - there is no need to dispose of the treated materials

Complete degradation of organics into CO2 and H2O in a relatively short period of time, i.e.do not introduce any new hazardous substances into the water.

Superior over other conventional methods of wastewater treatments, in the presence of bio - recalcitrant compounds

It can effectively degrade phenols, all halides, inorganic chemicals, dyes, herbicides, pesticides

Current Shortcomings1. Removal rate of SPC is relatively high while the Operating cost is

relatively expensive due to the use of reagents and irradiation sources

2. Some techniques require pre-treatment of wastewater to ensure reliable performance, which could be potentially costlier

3. Given the potential costs, SPC may not individually handle a large amount of wastewater; instead, it should be deployed in the final stage after primary and secondary treatment have successfully removed a large proportion of contaminants

SPC wastewater treatments hardly feasible for the industry scale up because:

- Poor attention from most of the scientific community towards energy intensification in SPC- Early stage of development- Lack of standard strategies for the design of large and efficient reactors.

Still many research needs in the field of SPC treatment for wastewater ,to provide:

– Better understanding of the mechanisms of SPC– Measurements of the efficiency of process under controlled experimental conditions– Realistic evaluations of the relative costs of candidate processes versus other treatment processes

Greater effort is needed to fully understand the difficulties in the degradation process:

- To reduce the cost of waste treatment - To improve existing and future applications

Current Scenario

Conclusion Sonophotocatalysis has provided promising results from a technical and

environmental point of views while the economics aspects are still being optimized.

Future dimensions of domain of SPC depending on consideration of optimization following parameters:

1) Operating time 2) Operating cost

Research on AOPs will surely bridge a gap between innovation, invention & its application towards society.Water is H2O, hydrogen two parts, oxygen one but there is also a third thing, that makes it water and nobody knows what that is.

–D.H. Lawrence (1885–1930)

References-1 .Aitali M.K, “Wastewater depollution by photo catalytic and biodegradation processes”, (2002)1-7.

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of Chemical Technology & Biotechnology, Volume 78, Number 11, November 2003 , pp. 1142-1148.

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Environmental 74 (2007) 63–72.

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Queries

??Any

Thank You…!