RELEASE AND STABILITY OF METAL NANOPARTICLES IN SURFACE WATER: EFFECTS OF PARTICLE LOADING

1. Tomsk Polytechnic University, Tomsk KTH Royal Institute of Technology, Stockholm RELEASE AND STABILITY OF METAL NANOPARTICLES IN SURFACE WATER: EFFECTS OF PARTICLE LOADING Elena Yunda Undergraduate Student, eny@tpu.ru Scientific advisors: Asst. Prof. Anna Godymchuk (TPU) Dr. Gunilla Herting (KTH) Prof. Inger Odnevall Wallinder (KTH) Tomsk- 2014

2. Outline • Background • Goal/Aim • Materials and Methods • Results and Discussion • Conclusions 2

3. Background Growth of NPs production Articles published on toxicity of NPs Annual growth rate + 29.8 % Number of articles NMs NMs toxicity NMs ecotoxicity [BBC Research] [Kahru A., 2009] • Increasing number and diversity of nanoparticlessources • Nanoparticles characteristics identify nanoparticlesbehavior in liquid environment Agglomeration Metal release • Lack of data on physicochemical behavior of nanoparticles in environmental media Sedimentation Change of surface charge 3

4. Aim Evaluate the effect of particle loading on nanoparticle stability and metal release in artificial surface water. Nanoparticles Experiment Exposure of NPs to solution Time: 60 minutes Temperature: 21°C Loadings: 10 and 100 mg/L Al Ni Zn S=15,5 m2/g S=6,0 m2/g S=13,6 m2/g Centrifugation of suspensions 10 minutes, ~3000 r/min Solution 100 nm Analysis of metal concentration in solution GF-AAS Evaluation of stability and average diameter of NPs PCCS * OECD - Organisation for Economic Co-operation and Development * GF-AAS - Graphite furnace atomic absorption spectroscopy * PCCS – Photon Cross-correlation Spectroscopy

5. Metal release and agglomeration of Al NPs Metal released after 15 minutes of exposure Loading: 10 … 100 mg/L 24μg/L 115μg/L • Low amounts of released aluminum in solution up to 1 h of exposure (<0.5% of the particle mass). • The surface of particles was more active in suspensions with lower loading. 1 min dm = 950 nm Aluminum NPs 100 mg/L 30 min dm = 1230 nm 60 min dm = 2700 nm • An increase of particles agglomeration with time.

6. Metal release and agglomeration of Zn and Ni NPs Metal released from Zn and Ni nanoparticles Agglomeration of Zn and Ni nanoparticles 60 min – all NPs settled • Decrease in concentration of particles in solution leads to an increase in solubility

7. Stability of NPs of Zn, Ni and Al in suspensions Zn 10 mg/L Ni 10 mg/L Al 10 mg/L • Loading 10 mg/L was below the limits of the instrument under chosen experimental conditions Ni 100 mg/L Zn 100 mg/L Al 100 mg/L • Zn and Ni NPs settled after 60 minutes of exposure. Al NPs were relatively stable for 1 hour.

8. Conclusions • Nanoparticles characteristics (size, amount of metal released, stability) changed significantly with time (agglomeration + gradual dissolution + sedimentation). • Reducing the loading of nanoparticles in solutionin 10 times increased the dissolution rate of Al in 2.5 times, Zn – in 3.1 times, Ni – in 2.2 times. • The loading of particles did not affect the kinetics of dissolution. • The influence of particles loading on the agglomeration process was not investigated due to the limits of the technique under chosen experimental conditions.

9. Acknowledgments Prof. Inger Odnevall Wallinder ingero@kth.se Dr. Gunilla Herting herting@kth.se PhD student Sara Skoglund sarasko@kth.se Ass. prof. Anna Godymchuk godymchuk@tpu.ru This work was supported by the scholarship of the President of the Russian Federation for studying abroad and performed at the Division of Surface and Corrosion Science at KTH Royal Institute of Technology, Stockholm, Sweden.