Catalytic applications of large scale metal processing wastes Justin Hargreaves

(i)Direct application as catalytic materials (ii)Direct use as pre-catalysts (iii)Modification to yield catalytically active phases (iv)Use as precursors for the synthesis of active catalysts Compositional variability Paradox

Waste materialReported production rate Red Mud120 million tonnes globally per annum Aluminium dross5 million tonnes globally per annum Fly ash430 million tonnes globally in 2003 Slag from Fe manufacture million tons globally in 2008 Chicken egg shells4 million tonnes annually in China alone Rice husk ash~ 70 million tonnes globally per annum M. Balakrishnan et al., Green Chem. 13, 16 (2011).

Al 89.1 Mg 3.8 Si 0.2 Pb 0.2 Zn 0.7 Ca 1.3 Na 0.7 K 0.8 Fe 2.5 Mn 0.6 Aluminium dross – aluminium production and recycling 5 x 10 6 t/year some dross recycled as deoxidiser in steel manufacture – rest in landfill Extracted metal content M. Balakrishnan et al., Green Chem. 13, 16 (2011).

Synthesis - structure directing agent, H 3 PO 4 and Cr(III) acetate added D= dross directly, E=extracted Al, P = pure Al(OH) 3 (commercial) AW removes more weakly bound Cr. J. Kim et al., J. Haz. Mater.169, 919 (2009)

Dross directly – impurities increase crystallite size Al extracted from dross Commercial Al source

Blast furnace slag x 10 6 t in 2008

Fly ash 430 x10 6 t in 2003

The chemical composition of fly ash and blast furnace slag (wt%) CaOSiO 2 Al 2 O 3 Fe 2 O 3 TiO 2 MgOMnOP2O5P2O5 K2OK2O Fly ash Blast furnace slag M. Balakrishnan et al., Green Chem. 13, 16 (2011).

Coal fly ash – zeolite synthesis One step (impure zeolite) – fly ash + 2M NaOH, 90°C, 96h Two step – fly ash + 2M NaOH, 90°C, 6h, filtration, add aluminate solution to adjust Si/Al to 0.8-2, incubate at 90°C for 24h G. Hollman et al., Fuel 78, 1225 (1999).

C. Pradhan et al., J. Chem. Technol. Biotechnol. 81, 659 (2006) para-tertiarybutylphenol is the desired product, HZOP-31 is a fly ash derived zeolite X

Zeolite synthesis from slag Materials containing in excess of 15wt% CaO unsuitable for zeolite synthesis – formation of calcium silicate inhibits zeolite nucleation Two stage method – react with H 3 PO 4 and then NaOH – hydroxyapatite/zeolite X composite New method – treat with HCl and then further treat leached solution and residual SiO 2

Y Kuwahara et al., J. Mater. Chem. 20, 5052 (2010).

Red Mud – waste product of the Bayer Process for Al manufacture Bauxite residue after treatment with caustic soda, extraction of liquid and drying Al 2 O 3.xH 2 O + 2NaOH  2NaAlO 2 + (x+1) H 2 O Variable composition, iron is a major phase, 120M tonnes produced per annum

RM4 & RM7 same site but 24 month interval ICP analysis

XRD analysis of red mud samples

CH 4 → C + 2H 2 Landfill Associated petroleum gas Flaring and associated NO X

Mass normalised hydrogen formation rates at 800  C CH 4 :N 2 =80:20, 60ml min -1, 0.4g

Maximum hydrogen formation rates at 800  C: RM4 (15m 2 g -1 ) x mol H 2 g -1 s -1 RM7 (14m 2 g -1 ) – 170 x mol H 2 g -1 s -1 RM6 (8m 2 g -1 ) – 50 x mol H 2 g -1 s -1 cf 4.58 x mol H 2 g -1 s -1 reported for 38 wt% Fe 2 O 3 /Al 2 O 3 at 800  C (K Otsuka and co-workers, J Catal. 222, 520 (2004))

Post 800  C reaction XRD analysis

RM 7 in-situ XRD, 72wt%C

Post 800  C reaction TGA in 2%O 2 /Ar RM wt%C, RM wt %C & RM wt%C

Derivative TGA

Butane cracking

72wt%C

RM 4 – 64wt% C

Acetonitrile – RM7

Ferromagnetism imparted by the presence of iron and iron carbide(s)

pH curves – raw RM7

Uptake of Pb ( ) and Cu (  ) by carbonised red mud.

Langmuir adsorption capacity of Cr, Cu and Pb on RM, ARM and CRM I. Pulford et al., J. Env. Manage. 100, 59 (2012)

R. Lago et al., Fuel 124, 7 (2014)

E. Karimi et al., Appl Catal B: Env 145, 187 (2014)

J. Kastner et al RSC Adv (2015)

Potential directions: generation of FeO 4 2- c.f. waste hydrated ferrous sulfate from sulfate process for TiO 2 production. N. Kanari et al., JOM, 53,11,32 (2001)

Acknowledgements: Ian Pulford, Vidya Batra, Malini Balakrishnan Hugh Flowers Jim Kastner and Jose Rico Snigdha Sushil, Nidhi Gupta, James Wigzell, Jilliann Clapp, Abdullah Alabdulrahman, Abdulrahman Al Harthi, Kim Wilson, Ross Blackley, Wuzong Zhou British Council, India – UKIERI Grant SA07-19

PZC – red mud

Carbonised RM7 – Cu 2+ adsorption data 0.5g carbonised red mud column experiments