Adsorptive Removal of Oxytetracycline Antibiotic in Aqueous Media using

Halloysite Nanoclay

1Ecosphere Resilience Research Center, Faculty of Applied Sciences, University of Sri Jayewardenepura,

Nugegoda, Sri Lanka 2Department of Animal and Plant Sciences, The University of Sheffield, Western Bank, Sheffield, UK

3Korea Biochar Research Center, O-Jeong Eco-Resilience Institute (OJERI) & Division of Environmental Science and Ecological Engineering, Korea University, Seoul 02841, South Korea

Sammani Ramanayaka1*, Meththika Vithanage1, Binoy Sarkar2, Yong Sik Ok3

Introduction Emerging contaminants

Different types of contaminants that have been detected in water bodies in trace levels Sources: • Waste water discharge • Surface runoff: Urban and Agricultural • Industrial • Ground water (e.g. landfills)

Pharmaceuticals

Personal care products

Pesticides

Industrial effluents Herbicides

Landfill leachate

https://www.healthcareglobal.com/top-10/top-10-innovative-pharma-companies-watch-2015 http://leachate.blogspot.com/p/what-is-leachate-landfill-leachaet.html

Introduction Contamination of Pharmaceuticals in Aquatic Environments

Antibiotics are among the top pharmaceutical contaminants released from non-

point and point sources. They are detected in elevated concentrations in ground

and surface water as emerging contaminants due to the extensive use by humans

and veterinary industry

Introduction Halloysite Nanoclay for removal of Antibiotic;

Oxytetracycline

• Antibiotics exhibit a poor capability of absorption (30%) in the digestive track

• Residuals are releasing to the environment via the body excretes

• Oxytetracycline hydrochloride (OTC) is a commonly used veterinary antibiotic,

which is detected high levels in water

R. Daghrir and P. Drogui, “Tetracycline antibiotics in the environment: a review,” Environ. Chem. Lett., vol. 11, no. 3, pp. 209–227, 2013.

Introduction Halloysite Nanoclay (HNC) for removal of Antibiotic

• Halloysite is a naturally occurring porous nanoclay material, which can be seen in impure forms, mixed with kaolinite, montmorillonite and other clay materials

• Porous nanoclay material consists of 10-15 bilayers of aluminosilicate rolled into a cylinder or tubular structure

• Si and O atoms have bound together forming fused siloxane tetrahedral sheet and an edge-shared octahedral sheet, which is made up of aluminium and hydroxide

K. Ramadass et al., “Halloysite nanotubes: Novel and eco-friendly adsorbents for high-pressure CO2 capture,” Microporous Mesoporous Mater., vol. 277, pp. 229–236, 2019.

Objectives Adsorptive removal of Oxytetracycline from aqueous using

Halloysite Nanoclay

• To assess the Oxytetracycline removal potential of HNC from aquatic environments

under different environmental conditions i.e. pH, ionic strengths, Time and different

initial OTC concentrations

• To postulate mechanisms behind adsorption

• To characterize HNC before and after oxytetracycline adsorption

Materials and Methodology Edge, Kinetic & Isotherm Experiments

Edge experiment

• Dosage of Halloysite: 1 g/L

• Suspension was hydrated for 4 hrs

• Nitrogen was purged in first 30 mins

• Initial pH of the solution: 9.97

• pH range: 3 to 9

• Spiked OTC concentration: 25 mg/L

• Ionic strengths: 0.1, 0.01, and 0.001 M NaNO3

Materials and Methodology Cont. Edge, Kinetic & Isotherm Experiments cont.

Kinetic experiment

• Dosage of Halloysite, and spiked OTC concentration were similar to the edge

experiment

• pH range: 4 to 5

• Ionic strength: 0.001 M NaNO3

• Time intervals of 2, 10, 20, 30, 45 min, and 1, 1.5, 2, 4, 8, 16, 24 h

Materials and Methodology Cont. Edge, Kinetic & Isotherm Experiments

Isotherm experiment

• Dosage of Halloysite: 0.5 g/L

• Suspension was hydrated for 4h and nitrogen was purged in first 30 mins

• Contact time: 12 h

• pH was adjusted to 4.75

• OTC concentration range: 10 – 500 mg/L

Characterization Methods

Powder x-ray diffraction (PXRD) Rigaku Ultima IV X-Ray Powder Diffractometer with a Cu Kα radiation (λ=1.54056 nm) over a 2θ range of 3-60°

Fourier Transformation Infrared Spectroscopy (FTIR)

Thermo scientific NICOLET (USA) Fourier Transformation Infra-Red spectrometer in the range of 550-4000 cm-1

Scanning Electron Microscopy (SEM) SEM images were obtained using a Field Emission Scanning Electron Microscope (FE-SEM Hitachi SU6600)

Particle size analyzer

UV/Vis spectrophotometer Thermo scientific GENESYS 10S Vis (USA) UV/Vis spectrophotometer in the range of 200-900 nm

HORIBA Scientific SZ-100 particle size analyzer in the scattering angle of 90°

Results & Discussion Powder X-ray diffraction (PXRD)

PXRD pattern of HNC depicts the characteristic sharp peaks at 2θ = 11.79° and 19.96° which is typical to Halloysite.

Halloysite PXRD pattern

PXRD pattern of Oxytetracycline hydrochloride

2 theta (degree)

Oxytetractcline hydrochloride PXRD pattern

Results & Discussion Fourier Transformation Infrared Spectroscopy (FTIR)

Oxytetracycline chemical structure

Oxytetracycline FTIR pattern Halloysite FTIR pattern

Results & Discussion Scanning Electron Microscopy (SEM)

SEM images of Halloysite nanotubes (a) Tubular structure (magnification x100 k) and (b) Occasional aggregates of nanotubes (magnification x50 k )

Results & Discussion Batch Experiments - Edge

• Oxytetracycline exists as a zwitterion in

the range of pH 3.5–7.5

• The point of zero charge (pHzpc) of HNC

was determined to be pH

Results & Discussion Batch Experiments - Kinetics

• A rapid adsorption was observed

during the first 120 mins reaching

an adsorption capacity of 17.5

mg/g

• The removal of OTC indicated

reaching equilibrium after 480

mins

• Data modeling demonstrates the

best fit for pseudo 2nd model

• The kinetic data modeling of the HNC-OTC interaction illustrates both intraparticle diffusion and

chemisorption as the mechanisms of complexation.

Results & Discussion Batch Experiments - Isotherm

Hill model

R2 0.913

Qmax 52.38 • Data modeling demonstrates the best fit to Hill

isotherm of OTC onto HNC

• The maximum adsorption capacity achieved by HNC

is 52.38 mg/g.

• Hill model dictates a cooperative adsorption where

multilayer adsorption takes place.

Results & Discussion After Adsorption

• Oxytetracycline adsorption to HNC was confirmed with the FTIR peak analysis

• Two main peaks of OTC can be clearly seen in the OTC adsorbed HNC

Results & Discussion Adsorption Mechanism

• In low pH values, pH 2.9 to pH 3.5, a cationic form of OTC complexes with negatively charged halloysite as the pHzpc is pH 2.9 via electrostatic interaction, which is non-specific adsorption

• Beyond pH 7.5, both OTC and halloysite become negatively charged and hence electrostatic repulsion reduces the OTC-halloysite interaction

• Al2O3 groups (+ve) and SiO2 groups (-ve) in the inner and outer lumens of HNC allows chemisorption with the tricarbonylamide and dimethylamine in the zwitterionic form of OTC during the pH of 2.5 to 8.0 through specific adsorption

Conclusions

• Oxytetracycline adsorption to the adsorbate HNC is clearly observed from FTIR results • The adsorption of Oxytetracycline is pH and ionic strength dependent and

demonstrates high adsorption capacity at the pH of 3.5

• OTC adsorption to HNC governs by both chemisorption and physisorption • Maximum adsorption capacity of HNC is observed as 21 mg/g

Adsorptive Removal of Oxytetracycline Antibiotic in Aqueous Media using Halloysite NanoclayIntroduction�Emerging contaminantsIntroduction�Contamination of Pharmaceuticals in Aquatic EnvironmentsIntroduction�Halloysite Nanoclay for removal of Antibiotic; OxytetracyclineIntroduction�Halloysite Nanoclay (HNC) for removal of AntibioticObjectives�Adsorptive removal of Oxytetracycline from aqueous using Halloysite NanoclayMaterials and Methodology�Edge, Kinetic & Isotherm ExperimentsMaterials and Methodology Cont.�Edge, Kinetic & Isotherm Experiments cont.Materials and Methodology Cont.�Edge, Kinetic & Isotherm ExperimentsCharacterization Methods Results & Discussion�Powder X-ray diffraction (PXRD)��Results & Discussion�Fourier Transformation Infrared Spectroscopy (FTIR)��Results & Discussion�Scanning Electron Microscopy (SEM)��Results & Discussion�Batch Experiments - Edge��Results & Discussion�Batch Experiments - Kinetics��Results & Discussion�Batch Experiments - Isotherm��Results & Discussion�After Adsorption��Results & Discussion�Adsorption Mechanism��Conclusions