Effects of High Salinity on Alginate Fouling during Ultrafiltration of High-Salinity Organic Synthetic Wastewater.

Weiwei Cai,Jingyu Zhang,Jingwei Wang,Qiuying Chen,Yan Li,Wenwen Xie

doi:10.3390/membranes11080590

Weiwei Cai, Jingyu Zhang + Show 4 more

Open Access

https://doi.org/10.3390/membranes11080590

Copy DOI

Abstract

Ultrafiltration is widely employed in treating high-salinity organic wastewater for the purpose of retaining particulates, microbes and macromolecules etc. In general, high-salinity wastewater contains diverse types of saline ions at fairly high concentration, which may significantly change foulant properties and subsequent fouling propensity during ultrafiltration. This study filled a knowledge gap by investigating polysaccharide fouling formation affected by various high saline environments, where 2 mol/L Na+ and 0.5–1.0 mol/L Ca2+/Al3+ were employed and the synergistic influences of Na+-Ca2+ and Na+-Al3+ were further unveiled. The results demonstrated that the synergistic influence of Na+-Ca2+ strikingly enlarged the alginate size due to the bridging effects of Ca2+ via binding with carboxyl groups in alginate chains. As compared with pure alginate, the involvement of Na+ aggravated alginate fouling formation, while the subsequent addition of Ca2+ or Al3+ on the basis of Na+ mitigated fouling development. The coexistence of Na+-Ca2+ led to alginate fouling formed mostly in a loose and reversible pattern, accompanied by significant cracks appearing on the cake layer. In contrast, the fouling layer formed by alginate-Na+-Al3+ seemed to be much denser, leading to severer irreversible fouling formation. Notably, the membrane rejection under various high salinity conditions was seriously weakened. Consequently, the current study offered in-depth insights into the development of polysaccharide-associated fouling during ultrafiltration of high-salinity organic wastewater.

Highlights

High-salinity organic wastewater, which refers to organic wastewater with salt content higher than 1%, is increasingly produced in recent years, especially from seafood processing, electroplating, petroleum industries, etc. [1,2,3]
The decrease in positive charges induced by Ca2+ probably resulted from the coordination of Ca2+ with carboxyl groups in the alginate chains, strikingly reducing surface potential to around +2.00 mV
The results showed the filtration outcomes of pure alginates and Na+ -Al3+ were best described by the cake filtration model

Summary

Introduction

High-salinity organic wastewater, which refers to organic wastewater with salt content higher than 1%, is increasingly produced in recent years, especially from seafood processing, electroplating, petroleum industries, etc. [1,2,3]. High-salinity organic wastewater, which refers to organic wastewater with salt content higher than 1%, is increasingly produced in recent years, especially from seafood processing, electroplating, petroleum industries, etc. The current effective techniques to treat high-salinity organic wastewater are still limited, as the highly saline environment hinders the biodegradation process and causes the invalidation of adsorption due to the presence of numerous ions [5]. Despite not being appropriate for removing ions, ultrafiltration (UF) and microfiltration (MF) have received increasing attention in current years for decontamination of high-salinity organic wastewater for the purposes of removing microbes, particles and various organics [7,8,9]. Membrane fouling is a great concern which hampers the sustainable operation of a membrane system and increases the cost of treatment [10,11,12,13,14], diverse fouling control methods have been proposed and developed to tackle fouling issues [15,16,17,18,19]

Methods

Results

Conclusion