Recycling of Spent Reverse Osmosis Membranes for Second Use in the Clarification of Wet-Process Phosphoric Acid

Khaoula Khaless,Rachid Boulif,Rachid Benhida,Brahim Achiou

doi:10.3390/min11060637

Khaoula Khaless, Rachid Boulif + Show 2 more

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https://doi.org/10.3390/min11060637

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Abstract

Various techniques have been used to “clean-up” wet-process phosphoric acid such as precipitation, flotation and adsorption. To address the potential of membrane processes in the phosphoric acid clarification process, this study explores the benefits of membrane techniques as a green separation technique for phosphoric acid clarification in an eco-efficient way through the use of recycling spent reverse osmosis membrane. Regenerated membrane was used to study the phosphoric acid clarification at a laboratory scale. They were immersed in an oxidizer for at most seven days. The samples were characterized systematically before immersion in an oxidant media. In this study, the potential to regenerate spent membranes and application of this media to clarify the 29% P2O5 phosphoric acid was demonstrated. This study shows, through experiments, that the reverse osmosis (RO) membranes could achieve a rejection of 70% and 61% for suspended solid and organic matter, respectively. These promising results will pave the way for implementation of these membranes in phosphoric acid treatment. Moreover, besides being economically advantageous, the use of the spent membrane is likely an environmentally friendly route (no waste, no organic solvent and effluent to be regenerated later on).

Highlights

Desalination of seawater using reverse osmosis (RO) is widely considered to be the most efficient and profitable way to produce of fresh water for populations and to treat water for industrial uses [1]
It is worth noting that no cracks and/or any other physical damage were detected, indicating that the spent membranes could likely support the hydraulic pressure during the filtration application
The experimental results showed that spent RO membrane was effectively transformed to MF membrane using NaOH, KMnO4, and KMnO4 /NaOH strippers

Summary

Introduction

Desalination of seawater using reverse osmosis (RO) is widely considered to be the most efficient and profitable way to produce of fresh water for populations and to treat water for industrial uses [1]. The spent membranes are commonly disposed to landfill in the classical waste management approach [3]. Sustainable management of end-of-life membranes is a challenge for desalination industries. Coutinho de Paula et al evaluated an environmental and economic evaluation of the benefits of recycling end-of-life RO membranes based on chemical oxidation of an aromatic polyamide-based active layer using sodium hypochlorite (NaClO, 10–12%) [3]. They showed that the recycled membrane has the features and performance of an ultrafiltration (UF) membrane. The recycled membrane was used for treating natural brackish water at the pilot scale and it is shown that the nanofiltration membrane has kept their performances during the four months of filtration

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