Sreenath Bolisetty and Raffaele Mezzenga

25 January 2016

Nature Nanotechnology

Department of Health Sciences and Technology, ETH Zurich,

AMYLOID–CARBON HYBRID MEMBRANES FOR UNIVERSAL WATER PURIFICATION

Main pollutants in wastewater

• Heavy Metals• Cyanides• Nuclear waste

Current technologies• Chemical precipitation is the most used = Secondary pollution

• Sorbets in ion exchange resins = Costly, small volumes.

• Flotation or electrochemical reactions = Specific metals, cost effective for high volumes

• Current technologies are expensive and ion specific

Membrane-based purification

• Micellar enhanced ultrafiltration

• Polymer enhanced ultrafiltration

• Reverse osmosis

• Nanofiltration• High costs• Fouling• Limiting feeding

flow

Self assembly

adsorbents

Specificity in heavy metal

removal

HYBRID MEMBRANES

• Protein amyloid fibres

• Porous activated carbon

Remove

• Heavy metal ions

• Radioactive waste

Schematic representation of amyloid–carbon adsorbers, and photographs of Na2PdCl4 solution changing colour from yellow to colourless after filtration

AFM of the β-lactoglobulin amyloids

S1. Atomic force microscopic (AFM) images of the β-lactoglobulin amyloids after high temperature treatment of the native monomer at 90° C and pH 2 for 5 h:

Composite activated carbon–amyloid fibril adsorber membrane

a, Structure of the β-lactoglobulin protein, 121-cys, with a lead ion attached. b, Amyloid-forming 121-cys-containing fragment (LACQCL) from β-lactoglobulin with docked Pb metal ions.. d, SEM image showing the surface of the composite membrane. e, Higher-magnification SEM demonstrating the assembly of the amyloid fibrils onto the activated carbon

• Amyloid forming peptides binds zinc an forms fabrics

• B lactoalbumin (cheap protein from milk) + Activated carbon

• Ensembles a mechanically strong composite

Docking poses of Hg ions at the 121-cys of the β-lactoglobulin

Docking poses of mercury ions at the 121-cys residue of the β-lactoglobulin protein sequence. (B) Amyloid-forming protein segment (LACQCL) docking with the mercury metal ions. (C) Amyloid forming segment (LACQCL) of the β-lactoglobulin protein generated from the zipperdb database server.

Concentrations of heavy metal and radioactive pollutants before and after filtration through the amyloid fibril–activated carbon hybridadsorber membrane

a, Potassium dicyanoaurate (I). b, Mercury chloride. c, Lead acetate. d, Disodium tetrachloropalladate. e, Uranyl acetate. f, Phosphorus-32. Insets in c and d: solution colour change before and after filtration.

Reusability of the filtration membrane in logarithmic-linear scale.

Calibration curves for concentration of heavy metal

pollutants before and after filtration through the hybrid

filter membranes. (A) Potassium dicyanoaurate, (B)

Mercuric chloride, (C) Lead acetate, (D) Disodium

tetrachloro palladate, (E) Uranyl acetate and (F)

Efficiency in removing pollutants simultaneously and after several cycles of filtration

a, Simultaneous single filtration event of water contaminated by four different heavy metal ions. b, Concentration of mercury chloride filtered by the same composite membrane for ten consecutive cycles. c, Efficiency of the composite membrane with different ratios of amyloid fibrils and controls with alternative membranes based on cellulose. d, Comparison of the relative specific adsorption capacity per filtration cycle of β-lactoglobulin amyloid fibrils (β-LG) and activated carbon (AC) for the four Au, Pd, Hg and Pb ion contaminants

Turning toxic gold ions into non-toxic gold nanoparticles and films.

a, UV–visible spectra of the catalytic reduction of p-nitrophenol (PNP) to p-aminophenol (PAP) by recovered gold nanoparticles. b, Plot of ln A (absorption at 400 nm) versus time for the catalytic reduction of PNP. c gold film recovered at 1,200 °C and its electrically conductive behaviour (d)

AFM of the recovered gold nanoparticles re- dispersed in water

Removal efficiencies by composite membranes having 2 wt% β-lactoglobulin amyloid fibrils at different pH conditions.

Gold nanoparticles production

TEM of gold nanoparticles recovered from the hybrid carbon-amyloid membrane by high temperature thermal treatment. Filtration of bacteria (Lactobacillus plantarum) by hybrid amyloid and activated carbon membranes. The solutions before (square) and after filtration (circle) were incubated in agar gel.

Conclusions

• Reduce polllutats 3 to 5 orders of magnitude

• Repeated passages

• Efficiency remains for severesl ions simultaneously

• Capture of valuable metals

• Nanoparticle and films production