In Situ Hybridization of Pulp Fibers Using Mg-Al Layered Double Hydroxides

Carl-Erik Lange,Mehedi Reza,Mika Lastusaari,Pedro Fardim,Pasi Kallio,Seyed Latifi

doi:10.3390/fib3020103

Carl-Erik Lange, Mehedi Reza + Show 4 more

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https://doi.org/10.3390/fib3020103

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Abstract

Inorganic Mg2+ and Al3+ containing layered double hydroxide (LDH) particles were synthesised in situ from aqueous solution onto chemical pulp fibers of pine (Pinus sylvestris). High super saturated (hss) solution with sodium carbonate produced LDH particles with an average diameter of 100–200 nm. Nano-size (70 nm) LDH particles were found from fibers external surface and, to a lesser degree, from the S2 cell wall after synthesis via low super saturated (lss) route. The synthesis via slow urea hydrolysis (Uhyd) yielded micron and clay sized LDH (2–5 μm) and enabled efficient fiber densification via mineralization of S2 fiber wall layer as indicated by TEM and compliance analysis. The Uhyd method decreased fiber compliance up to 50%. Reduction in the polymerisation degree of cellulose was observed with capillary viscometry. Thermogravimetric analysis showed that the hybridization with LDH reduced the exothermic heat, indicating, that this material can be incorporated in flame retardant applications. Fiber charge was assessed by Fibers 2015, 3 104 adsorption expermients with methylene blue (MB) and metanil yellow (MY). Synthesis via lss route retained most of the fibres original charge and provided the highest capacity (10 μmol/g) for anionic MY, indicating cationic character of hybrid fibers. Our results suggested that mineralized fibers can be potentially used in advanced applications such as biocomposites and adsorbent materials.

Highlights

A great deal of research that concentrates on layered double hydroxide (LDH) particles is related to composite structures with various polymeric matrices [1,2] and sorption processes for water purification applications [3,4], and to coating technology, especially in corrosion protection [5,6,7], and to different catalytic processes [8,9]
We address the chemical and physical characteristics of pulp fibers considering the changes in cellulose polymer chain length, adsorption capacity, thermal behavior and compliance after the lss, hss and urea hydrolysis (Uhyd) synthesis routes, which all involve in situ LDH particle synthesis on fiber surfaces
Effective LDH particle nucleation on fiber surface was succesfully conducted in aqueous medium of low super saturated, high super saturated and slow urea hydrolysis (Uhyd) synthesis methods

Summary

Introduction

A great deal of research that concentrates on layered double hydroxide (LDH) particles is related to composite structures with various polymeric matrices [1,2] and sorption processes for water purification applications [3,4], and to coating technology, especially in corrosion protection [5,6,7], and to different catalytic processes [8,9]. Electrochemical applications, such as batteries [10], capacitors [11]. Other synthesized natural-like minerals that are included in the hydrotalcite group are the ones where Mg2+ is replaced by Zn2+ [19,20,21] as in zaccagnaite or by

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