Adsorption of Oxy-Anions in the Teaching Laboratory: An Experiment To Study a Fundamental Environmental Engineering Problem

Abstract

Synthesizing and testing bicomposite adsorbents for the removal of environmentally problematic oxy-anions is high on the agenda of research-led universities.Here we present a laboratory module successfully developed at Imperial College London that introduces the advanced undergraduate student in engineering (chemical, civil, earth) and science (chemistry, materials, earth science) to several fundamental principles associated with this research area in a simple, engaging and safe way. This includes (i) the synthesis of inorganic bicomposite sorbents, (ii) the evaluation of the adsorption−removal process, and (iii) the analysis of the sorbate; all underpinned by theory. We devise an experiment using phosphate oxyanions and an iron−titanium oxide bicomposite sorbent, which is simple to synthesize. The adsorption of phosphate solutions of varying concentration is tested and assessed at pH 5 and 9. Phosphate concentrations at equilibrium are analyzed using UV−vis spectroscopy to plot adsorption isotherms and compare the Langmuir and Freundlich models. This topical introduction to environmental engineering is an excellent opportunity to investigate adsorption processes. The complexity of data interpretation can be tailored to a range of abilities, and the topics addressed in the experiment are relevant starting points for further exploration of environmental geochemistry, pollution control, element transport, and adsorption. We present ready-to-use spreadsheets for the students to facilitate data analysis.

Determining the Effect of pH on Iron Oxidation Kinetics in Aquatic Environments: Exploring a Fundamental Chemical Reaction To Grasp the Significant Ecosystem Implications of Iron Bioavailability

“…This experiment has been successfully run and continuously developed at Imperial College London for six years now, and it forms part of the Environmental Geochemistry laboratory course that undergraduate students of Earth Science and Engineering take in their third year. We have presented three units of that course in this Journal . − The laboratory course builds upon a classroom lecture given in year 2 where the students learn the basics of environmental chemistry and use the textbooks of Stumm and Morgan and of Eby as accompanying literature for referencing. The exercise discussed here was originally designed by the group of Professor Laura Sigg at ETH Zurich and, on the basis of the experiments described by Stumm and Lee, was adapted and developed to our laboratory class successfully.…”

How the conditioning and storage of samples for SEM-EDX analysis may influence the interpretation of diffusion mechanisms in the sorption of metals ions by extractant impregnated resins

“…Au(III) solutions were prepared in 0.01 mol L −1 HCl solutions. Conventional procedures for the study of sorption properties have been followed . The sorption experiments at equilibrium were performed by mixing the resin (0.020 g) with Au(III) solutions (0.010 L; 300 mg Au L −1 ) for one week with a solid/liquid ratio (sorbent dosage, SD) fixed to m/V = 2 g L −1 (m: mass of sorbent, g; V: volume of solution, L).…”

Teaching Adsorption Chemistry by Constructing Surface Complexation Models (SCM) in PHREEQC

“…The modeling experiment can be coupled with wet chemistry (as per the undergraduate courses), 35 or taught as a standalone class, if sufficient theory is provided (as per the workshop). An interesting application of this class might be the remote delivery of practical exercises when wet lab facilities are not available.…”

“…32 In their experiment, the adsorbate is a high surface area metal−organic framework (MOF-808), introducing students to designer adsorbents for the removal of emerging contaminants. In some experiments, the adsorbent is first synthesized, 1,35,32 offering opportunities for students to consider the physical and chemical properties that make an effective adsorbent. Students develop analytical chemistry skills, using background subtraction and external calibration curves.…”