Aniline modified cross-linked starch from commercial rice (oryza sativa) flour : a novel material for arsenic removal from contaminated water

Date

4-2013

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Milagros M. Peralta

Restrictions

Restricted: Not available to the general public. Access is available only after consultation with author/thesis adviser and only to those bound by the confidentiality agreement.

Abstract

Rice (Oryza sativa) starch was isolated from rice flour using standard methods and its molecular weight was determined to be 5.01 107 Da using Canon-Fenske viscometer. This corresponded to a degree of polymerization of 3.09 x 105. The purified rice starch was used to prepare cross-linked starch (CS) and aniline modified cross-linked starch (AMCS). CS was prepared by mercerizing rice starch using 1.2 g NaOH per 5 g dry starch at 80°C for 30 minutes and cross-linking it using 1:3, 1:5 and 1:7 starch: formaldehyde molar ratios at 50°C for 24 hours. AMCS was prepared by reacting rice starch with p-toluenesulfonyl chloride dissolved in 3:2 v/v pyridine: H2O at 85°C for 30 minutes, then converting tosyl starch with starch, aniline and formaldehyde in molar ratios of 1:1:5 and 1:1:7 starch: aniline: formaldehyde at 50°C for 24 hours. The solubility and swelling indices of CS and AMCS were determined at room temperature using different solvent of different pH values. Statistical results showed that the differences in the solubility and swelling indices were found to be significant. The optimum cross-linking ratio for CS (1:5starch: formaldehyde) and AMCS (1:1:7 starch: aniline: formaldehyde) were characterized as being insoluble but having good swelling power. SEM analysis CS (1:5starch: formaldehyde) was found to have the size varying from 51.8 nm to 187 nm while for AMCS, the size varies from 130 nm to 307 nm.Only a part of CS was on the nanoscale level while AMCS was totally not on the nanoscale level. From the potentiometric titration of AMCS, its pKa was found to be 6.71 which was higher than that of the anilinium ion (pKa 4.7). Arsenic (As) removal from contaminated water using CS and AMCS was spectrophotometrically done using the modified ascorbic acid method via simultaneous determination of phosphates and arsenates. The absorbance values for phosphates and arsenates were read at 880 nm and 820 nm, respectively. Correspondingly, the maximum interaction time for the ratio 1 g adsorbent/100 mL of arsenate solution for CS and AMCS were found to be 4 hours (60% removal) and 2 hours (80% removal). Also, the maximum loading capacity of the same amount of CS and AMCS were 60 ppm and 67 ppm, respectively. Increasing the amounts of CS and AMCS resulted to an increase in the amount of As being removed. Using 5 g adsorbent/100 mL of arsenate solution, CS can remove up to 93% while AMCS can remove up to 99% considering 80 ppm of total As content. As applied to deep well water sample having a total of 0.735 ppm As, 97.1% was removed using CS and 99.7% using AMCS, Hence, AMCS was concluded to be a better adsorbent than CS for the removal of As from contaminated water.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2013 C42 /A85

Document Type

Thesis

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