Green Sorbent Research Articles

Effectiveness of Aluminum-based Drinking Water Treatment Residuals as a Novel Sorbent to Remove Tetracyclines from Aqueous Medium

Low levels of various veterinary antibiotics (VAs) have been found in water resources across the United States as a result of nonpoint-source pollution. As the first phase of developing a potential green sorbent for tetracycline (TTC) and oxytetracycline (OTC), we examined the effects of solution chemistry, pH, ionic strength (IS), sorbate:sorbent ratio (SSR), and reaction time on TTC and OTC sorption by a waste byproduct of the drinking-water treatment process, namely, Al-based drinking-water treatment residuals (Al-WTR). The sorption of TTC and OTC on Al-WTR increased with increasing pH up to pH 7 and decreased in the pH range of 8 to 11. A concentration of 20 g L was deemed as optimum SSR, where more than 95% of the initially added TTC and OTC were sorbed and equilibrium was reached in 2 h. A pseudo-second-order model ( = 0.99) was used for Al-WTR sorption for TTC and OTC. The data best fit the linearized form of the Freundlich isotherm ( = 0.98). No significant effect ( > 0.05) of IS on sorption of TTC and OTC was observed between 0.05 and 0.5 mmol L. However, at higher initial concentrations (>1 mmol L), IS dependence on TTC and OTC sorption was observed. Surface complexation modeling and Fourier transform infrared spectroscopy analysis indicated the possibility of TTC and OTC forming a mononuclear monodentate surface complex through strong innersphere-type bonds on Al-WTR. The results show promising potential of Al-WTR for use as a "green" and cost-effective sorbent to immobilize and stabilize TTC in soils and waters.

A green sorbent of esterified egg-shell membrane for highly selective uptake of arsenate and speciation of inorganic arsenic

Egg-shell membrane (ESM) is a promising adsorbent for heavy metal uptake. However, carboxylic groups on ESM surface barrier arsenic adsorption. Herein, ESM is modified by esterification and the methyl esterified egg-shell membrane (MESM) possesses positive charge within pH 1–9. As a novel green sorbent material, MESM exhibits 200-fold improvement on sorption capacity of arsenate with respect to bare ESM. It presents an ultra-high selectivity of 256:1 toward arsenate against arsenite. At pH 6, 100% sorption efficiency is achieved for 2μgL−1 As(V) by 10mg MESM, while virtually no adsorption of As(III) is observed. This provides great potential for selective sorption of arsenate in the presence of arsenite. By loading 4.0mL sample within 0.05–5.00μgL−1 As(V) followed by elution with 300μL HCl (1.5molL−1), a detection limit of 15ngL−1 is obtained along with a RSD of 3.5% at 0.5μgL−1. Total inorganic arsenic is achieved by converting As(III) to As(V) and following the same sorption process. This procedure is applied for arsenate determination and inorganic arsenic speciation in Hijiki and water samples. The results are confirmed by graphite furnace atomic absorption spectrometry and spiking recovery.

Selective Adsorption of Cr (VI) in Industrial Waste Water Using Green Sorbent Materials

Selective Adsorption of Cr (VI) in Industrial Waste Water Using Green Sorbent Materials

Uptake and Speciation of Inorganic Arsenic with Cellulose Fibre Coated with Yttrium Hydroxide Layer as a Novel Green Sorbent

AbstractA novel adsorbent was developed by coating yttrium hydroxide precipitate layer on cellulose fibre. This material takes up ca. 98% of 5 µg·L−1 As(III) and As(V) at low pH (pH<7), while a favorable selectivity for As(V) was achieved within pH 11–12. In practice, a mini‐column packed with Y(OH)3 precipitate layer coated cellulose fibre particles was incorporated into a sequential injection system for selective uptake of arsenate at pH 11.5. The retained arsenate was afterwards recovered with 50 µL of 0.8 mol·L−1 NaOH solution as eluent, followed by hydride generation in a reaction medium of 2.0 mol·L−1 HCl and 1.0% NaBH4 solution (W/V, in 0.5% NaOH) after pre‐reduction of arsenate to arsenite by KI‐ascorbic acid (5%, W/V), with detection by atomic fluorescence spectrometry. Total inorganic arsenic was quantitatively taken up at pH 6.0 by following the same procedure and arsenic speciation was performed by difference. With a sample volume of 1.0 mL, an enrichment factor of 16.4 was derived with a detection limit of 17 ng·L−1 within a linear range of 0.05–2.0 µg·L−1. A relative standard deviation (RSD) of 2.6% (0.5 µg·L−1, n=11) was achieved. The procedure was validated by analyzing arsenic in a certified reference material GBW 09101 (human hair), and speciation of inorganic arsenic in natural water samples. The entire process requires no organic solvents, thus Y(OH)3 coated cellulose fibre provides a green adsorbent.