Strength of Flocs Formed by the Complexation of Lysozyme with Leonardite Humic Acid.

Wan Khairunnisa Wan Abdul Khodir,Azizul Hakim,Motoyoshi Kobayashi

doi:10.3390/polym12081770

Wan Khairunnisa Wan Abdul Khodir, Azizul Hakim + Show 1 more

Open Access

https://doi.org/10.3390/polym12081770

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Journal: Polymers	Publication Date: Aug 7, 2020
Citations: 2	License type: CC BY 4.0

Affiliation: University of Chittagong, University of Tsukuba

Abstract

Aggregation and aggregates properties of natural organic and nanosized macromolecules such as humic substances and proteins are crucial to explore so-called colloid-mediated transport and the fate of substances in soil and water environments. Therefore, the aggregation and dispersion, charging, and floc strength of lysozyme (LSZ)–leonardite humic acid (LHA) flocs were experimentally investigated. The experiments were performed in different salt concentrations and LSZ to LHA mass ratios as a function of pH. We obtained the stronger flocs at pH 4.4, where the isoelectric point (IEP) of the complex with the mass ratio 2.5 was confirmed. Thus, the aggregation of LSZ–LHA flocs is mainly caused by charge neutralization. We obtained the floc strength of 4.7 nN around IEP at low salt concentration of 3 mM, which was stronger than 2.8 nN in high salt concentration of 50 mM. The effect of salt concentration can be rationalized by charge-patch attraction at low salt concentration. With increasing mass ratio, the IEP shifted to higher pH. This is due to the increase in positive charge from LSZ in the mixture. The effect of the LSZ to LHA mass ratio on the maximum strength was weak in the range studied.

Highlights

In soil and water environments, there are a lot of colloidal and nanosized particles and macromolecules such as clays and natural organic matters
Verwey–Overbeek (DLVO) forces [2,3], which are composed of van der Waals and electrical double layer (EDL) forces
At lower pH, the electrophoretic mobility (EPM) of the complexes at all KCl concentrations appeared as a positive value until reaching zero mobility or isoelectric point (IEP) at pH 4.5

Summary

Introduction

In soil and water environments, there are a lot of colloidal and nanosized particles and macromolecules such as clays and natural organic matters. It is of great importance to predict and control the transportation of these particles. The movement of such particles and macromolecules through a soil pore entirely depends on the size of the particles [1]. Hydrodynamic force can disaggregate the floc/aggregate during the transportation. The strength of a floc/aggregate against breakage [1,4,5,6,7,8] is considered as an important parameter to predict the movement of these particles in soil and water environments

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Conclusion