A New Type of Adsorbent Based on the Immobilization of Humic Acid on Chitin and Its Application to Adsorb Cu(II)

Abstract

Synthesis of a new type of adsorbent has been conducted by immobilizing peat soil humic acid (HA) on chitin isolated from crab shell waste. The adsorbent was then applied to adsorb Cu(II) in aqueous medium. The HA was extracted from peat soil of Gambut District, South Kalimantan, Indonesia; while the chitin was isolated from marine crab shell waste of seafood restaurants. The extraction of HA was performed by the commonly used alkaline extraction in NaOH 0.1 M solution, and the isolation of chitin was conducted through deproteination using NaOH 3.5%(w/v) and followed by removal of inorganic impurities using HCl 1 M. The extracted HA and the isolated chitin were characterized by Fourier Transform Infra Red (FT-IR) spectroscopy. Parameters investigated in this study consisted of method of HA immobilization on chitin, stability test of the immobilized HA, as well as rate, capacity, and energy of adsorption. The FT-IR spectra revealed the presence of main functional groups of COOH and OH (phenolic-and alcoholic-OH) in HA, and those of NH, C=O, CH3, and OH groups in chitin. The immobilization of HA on chitin was successfully done by reacting gelatinous chitin (40 g) in 250 mL of HCl 0.5 M and solution of HA (4 g) in 500 mL of NaOH 0.5 M. This immobilization produced an adsorbent of humic acid immobilized on chitin (Chitin-HA) with the content of HA was 1.98%(w/w). The HA immobilized was stable in the acidity range of pH 3.0 to 11.0. At the acidity giving maximum adsorption, i.e. pH 4, the first order rate constant, capacity, and energy of adsorption of Cu(II) on the HAC were 4.6 × 10 −4 min-1, 0.282 mmol/g, and 20.35 kJ/mol, respectively. Compared to the adsorption of Cu(II) on chitin, the first order rate constant and capacity of adsorption of Cu(II) on the Chitin-HA were, respectively, 1.24 and 1.42 time higher; while the adsorption energy was 0.90 time smaller.

Chitin–humic acid hybrid as adsorbent for Cr(III) in effluent of tannery wastewater treatment

“…The mixture was stirred continuously for 24 h and then aged for 6 h. The mixed solution was filtered, and the precipitation was washed and dried in oven at 50-60 8C. Procedure in detail has already described in our previous paper [15].…”

“…Our previous study has successfully immobilized humic acid (HA) on chitin and compared to chitin, this chitin-HA hybrid has better performance in removing Cu(II) [15], Ni(II) [16], and Cr(III) [17] from aqueous solution. In this study, the performance of chitin-HA hybrid is further evaluated to remove Cr(III) in real effluent of tannery wastewater treatment after performing rigorous optimation using synthetic effluent sample.…”

The Role of Carboxyl and Hydroxyl Groups of Humic Acid in Removing AuCl₄^- from Aqueous Solution

“…It should be noted that the purified HA was obtained from the crude HA after repeated purifications with a mixed solution of HCl and HF, followed by intensive washing with water until the supernatant was neutral. Under neutral conditions, nearly all the -COOH groups of the purified HA should be deprotonated to -COO− groups [16,[33][34]. On the other hand, utilization of the purified HA as an adsorbent was undertaken at low pH and hence all the -COO− groups had been converted to -COOH groups.…”

“…Humic acid (HA) comprises the fraction that is insoluble at low pH, fulvic acid (FA) is the fraction that is soluble over a wide pH range, and humin is the fraction that is insoluble at any pH value [9]. For the HA extracted from peat soil, its excellent performance as an adsorbent has been confirmed for a variety of metals, such as Ag(I) [10], Al(III) [11], Cd(II) [12][13], Cr(III) [14][15], Cu(II) [16][17], Fe(III) [18], Mn(II) [19] and Ni(II) [20]. This performance is even higher after immobilizing the HA on silica gel [21], chitin [15,20], chitosan [12,22] and bentonite [23].…”

Immobilization of Humic Acid Onto Chitosan Using Tosylation Method With 1,4-Butanediol as a Spacer Arm

“…Several approaches for immobilization of HA have been suggested [22][23][24][25][26]. Unfortunately, these immobilization methods gave an implication on reducing the most active sorption site of HA because of reducing the number of carboxylic group as the most active sorption site during immobilization process.…”