Adsorption–Desorption Behavior of Arsenate Using Single and Binary Iron-Modified Biochars: Thermodynamics and Redox Transformation

Abstract

Arsenic (As) is a dangerous contaminant in drinking water which displays cogent health risks to humans. Effective clean-up approaches must be developed. However, the knowledge of adsorption–desorption behavior of As on modified biochars is limited. In this study, the adsorption–desorption behavior of arsenate (As V ) by single iron (Fe) and binary zirconium–iron (Zr–Fe)-modified biosolid biochars (BSBC) was investigated. For this purpose, BSBC was modified using Fe-chips (FeBSBC), Fe-salt (FeCl 3 BSBC), and Zr–Fe-salt (Zr–FeCl 3 BSBC) to determine the adsorption–desorption behavior of As V using a range of techniques. X-ray photoelectron spectroscopy results revealed the partial reduction of pentavalent As V to the more toxic trivalent As III form by FeCl 3 BSBC and Zr–FeCl 3 BSBC, which was not observed with FeBSBC. The Langmuir maximum As V adsorption capacities were achieved as 27.4, 29.77, and 67.28 mg/g when treated with FeBSBC (at pH 5), FeCl 3 BSBC (at pH 5), and Zr–FeCl 3 BSBC (at pH 6), respectively, using 2 g/L biochar density and 22 ± 0.5 °C. Co-existing anions reduced the As V removal efficiency in the order PO 4 3– > CO 3 2– > SO 4 2– > Cl – > NO 3 – , although no significant inhibitory effects were observed with cations like Na + , K + , Mg 2+ , Ca 2+ , and Al 3+ . The positive correlation of As V adsorption capacity with temperature demonstrated that the endothermic process and the negative value of Gibbs free energy increased (−14.95 to −12.47 kJ/mol) with increasing temperature (277 to 313 K), indicating spontaneous reactions. Desorption and regeneration showed that recycled Fe-chips, Fe-salt, and Zr–Fe-salt-coated biochars can be utilized for the effective removal of As V up to six-repeated cycles.

The efficacy of Pb, As(v) and Sb(iii) removal by biochar is determined by solution chemistry

“…In highly P rich systems, where As( v ) to P molar ratios are lower than our current value of 1 : 29, competition effects can be more drastic. 58,59 Lack of competition effects could also be ascribed to P precipitation as Ca–P phases (such as hydroxyapatite and calcium phosphate) 60 at the high pH of BCD solutions (∼9.5–9.8) that drove P depletion from solution independently. The density of P on BCD at high Ca concentrations was higher than at low Ca concentrations (Fig.…”

A review of mechanism and adsorption capacities of biochar-based engineered composites for removing aquatic pollutants from contaminated water

“…After four consecutive cycles, the composite still exhibited a 90% sulfamethoxazole adsorption efficiency compared with its worth for pristine adsorbent (Heo et al, 2019). Sun et al (2022) reported that the FeCl 3 -BC composite showed higher adsorption capacities for sulfamethoxazole, sulfamethazine, and sulfadiazine as 454, 400, and 294 mg g −1 , respectively, compared to the unmodified adsorbent. This could be attributed to the higher surface area of composite, H-bonding between -COOH/-OH groups in adsorbent and antibiotics molecules.…”

“…Details of various pyrolysis mechanism conditions and product yield. TABLE 2 Published reviews based on the biochar application in the removal of various types of pollutants in water(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020)(2021)(2022).…”

Metal‐Loaded Biochar for the Removal of Arsenic from Water: A Critical Review on Overall Effectiveness, Governing Mechanisms, and Influential Factors

“…Saccharum spontaneum Kans grass straw 13.5 Fe 3 O 4 2.0 mg g À 1 3.1 mg g À 1 Baig et al [137] 16. Rahman et al [138] ChemistrySelect maximum adsorption of 33.7 g kg À 1 for peanut straw and 27.0 g kg À 1 for rice straw biochars modified with Fe(III) at pH 5.…”