University of Oulu

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Author: Zhang, Ruichi1
Organizations: 1University of Oulu, Faculty of Technology, Environmental Engineering
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.4 MB)
Persistent link: http://urn.fi/URN:NBN:fi:oulu-201710112970
Language: English
Published: Oulu : R. Zhang, 2017
Publish Date: 2017-10-18
Physical Description: 64 p.
Thesis type: Master's thesis (tech)
Tutor: Leiviskä, Tiina
Reviewer: Leiviskä, Tiina
Description:

Abstract

Increasing discharged anionic pollutants discharged into water has been a subject of concern worldwide. Although numerous conventional methods are used to treat these anion contaminated wastewater, most of them have their own limitations such as high investment cost, sensitive operation conditions, and sludge handling problems. Low-cost biosorbents have attracted a lot of attention for anion removal due to their abundance source, high availability, renewability and environmental sustainability. Four type of iron–modified biomaterials: sawdust, CA-sawdust (citric acid modified sawdust), peat and peat moss residue (PMR) were tested in the preliminary experiment for phosphate sorption. PMR was then selected as optimum biomass for phosphate removal based on its good phosphate removal efficiency. The effect of modification conditions: initial Fe(III) concentration (0.067 g Fe³⁺/50 mL, 0.133 g Fe³⁺/50 mL, and 0.201 g Fe³⁺/50 mL) and modification pH (5, 7 and 9) were investigated. Modification pH 5 and initial Fe(III) concentration (0.201 g Fe³⁺/50 mL) was observed to be the optimal condition for PMR modification, and then was selected for further studies. Phosphate sorption tests were carried out at room temperature as a function of solution pH (3–9) and contact time (30 mins, 60 mins, 1 h, 6 h and 24 h) at an initial phosphate (P) concentration of 15 mg/L. The removal efficiency decreased with increasing pH within the range of 3–9 and the maximum removal efficiency (82%) was observed at pH 3 after 24 hours contact time. However, considering low pH is not always practical to be applied in real industrial activities, thus the pH 4 was perceived as optimal pH in this study. The effect of the contact time on phosphate sorption was conducted at pH 4. With the increased contact time, the phosphate removal efficiency increased and reached to 70% at 24 hours contact time. Two batches (batch 1 and batch 2) were used to obtain the maximum capacity of iron-modified PMR at the initial phosphate (P) concentration in the range of 10 to 175 mg/L at pH 4 under the room temperature. Batch 1 was used also for all the sorption tests, while batch 2 was used only for maximum capacity tests. The maximum capacity was 9 mg/g and 13 mg/g for batch 1 and batch 2 at initial phosphate (P) concentration of 104 mg/L and 175 mg/L, respectively. The sorption followed the Langmuir isotherm but the results were opposite for non-linear model. Results showed that iron-modified PMR can be used effectively as a biosorbent for phosphate removal from aqueous solutions. XRD analyses showed that iron compound loaded on the PMR was amorphous iron oxyhydroxide, which was supposed to be two-line ferrihydrite. XPS analyses supported this finding.

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