Abstract
The renewable pine needles was used as an adsorbent to remove phosphorus from aqueous solutions. Using batch experiments, pine needles pretreated with alkali-isopropanol (AI) failed to effectively remove phosphorus, while pine needles modified with lanthanum hydroxide (LH) showed relatively high removal efficiency. LH pine needles were effective at a wide pH ranges, with the highest removal efficiency reaching approximately 85% at a pH of 3. The removal efficiency was kept above 65% using 10 mg/L phosphorus solutions at desired pH values. There was no apparent significant competitive behavior between co-existing anions of sulfate, nitrate, and chloride (SO4 2-, NO3 - and Cl-); however, CO3 2- exhibited increased interfering behavior as concentrations increased. An intraparticle diffusion model showed that the adsorption process occurred in three phases, suggesting that a boundary layer adsorption phenomena slightly affected the adsorption process, and that intraparticle diffusion was dominant. The adsorption process was thermodynamically unfavorable and non-spontaneous; temperature increases improved phosphorus removal. Total organic carbon (TOC) assays indicated that chemical modification reduced the release of soluble organic compounds from 135.6 mg/L to 7.76 mg/L. This new information about adsorption performances provides valuable information, and can inform future technological applications designed to remove phosphorus from aqueous solutions.
Highlights
Phosphorus plays a critical role in the development of ecosystems, agriculture, and industry, and becomes a pollutant in water bodies [1, 2]
White fine spots were observed on the interior of lanthanum hydroxide (LH) pine needlesand these spots were confirmed as lanthanum oxide according to EDAX spectrum, and 11.84% of La was apparent in LH pine needles, (S1 Fig, seen in the supporting information)
SEM photographs and EDAX analysis clearly showed that chemical treatment and LH precipitation resulted in many pores and adsorption site production
Summary
Phosphorus plays a critical role in the development of ecosystems, agriculture, and industry, and becomes a pollutant in water bodies [1, 2]. To meet increasing demands for phosphorus, more and more phosphate ore reserves are being exploited. Current reserves will be depleted in 50–100 years [3,4,5], highlighting the important need to identify new ways to recycle and reuse phosphorus [6]. Biosorbents are important tools for chemical recover and recycling. They are environmentally friendly, cost-effective, and available from industrial, agricultural, and other types of PLOS ONE | DOI:10.1371/journal.pone.0142700. They are environmentally friendly, cost-effective, and available from industrial, agricultural, and other types of PLOS ONE | DOI:10.1371/journal.pone.0142700 December 2, 2015
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