Phosphorus Recovery by Liquid-Liquid Extraction
Abstract:It is acknowledged that phosphorus removal is more crucial in comparison with nitrogen removal for preventing algae glooming and eutrophication. Chemical and biological methods are common methods for the P removal. Excessive sludge production and difficulties of recovering phosphorus are concerns in terms of sustainable waste management. A liquid-liquid extraction (LLE) process is thus considered for the study aiming at recovering phosphorus from wastewater in a sustainable way. The results revealed that the best extractant is a mixture of kerosene and benzyl-di-methyl-amine (BDMA) at a volume ratio of 2:1. Under the study conditions, one part of extractant can react with four parts of wastewater to transfer >97% of P to the organic phase. In addition, in the stripping step, a 1:1 ratio of extract to recycled acid can result in 96% recovered P, implying an overall 93% phosphorus recovery efficiency can be achieved by the LLE process. Most importantly, the extractant can be recycled and reused at least 5 times if the residual P concentration should be less than 4 mg/L vs. the original P concentration of 21 mg/L. A complexion between amine groups in BDMA and phosphates and the positive charge of the micelles surface when the extractant (composed of kerosene and BDMA) mixed with P containing wastewater would contribute to the P recovery and this is a novel approach to recover P from wastewater.
Document Type: Research Article
Affiliations: Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey, UK
Publication date: January 1, 2009