Experimental Studies on the Removal of Aluminium Ions from Synthetic Aqueous Solution by Hydroxyapatites.

Doina Humelnicu,Maria Ignat,Inga Zinicovscaia,Ionel Humelnicu

doi:10.17344/acsi.2021.6830

Abstract

In this work we have presented the results obtained in the adsorption behavior of hydroxyapatite with different treatment towards aluminium ions from synthetic wastewaters. Experiments were performed in batch technique at different pH values, temperatures, sorbent dosage, contact time and initial aluminium concentration. The thermodynamic studies on the adsorption process of aluminium onto hydroxyapatite indicated that the process is spontaneous and endothermic. The Langmuir, Freundlich, Flory-Huggins, Dubinin-Radushkevich and Temkin equilibrium models were applied to the description of experimental data. The adsorption of aluminium follows the Langmuir adsorption isotherm. The kinetics of adsorption was evaluated using the pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models. The rate of aluminium adsorption was successfully described by a pseudo-second-order kinetic model. The obtained results indicated that hydroxyapatite treated with Pluronic P123 surfactant has a higher sorption capacity toward aluminium ions (117.65 mg g-1) than hydroxyapatite treated with Pluronic F127 surfactant (109.89 mg g-1) while untreated hydroxyapatite exhibited the lowest one (104.17 mg g-1).

Highlights

Wastewaters that contain metals are considered to be dangerous to both human and the environment due to their acute toxicity and non-biodegradability, even when the metals are present at very low concentrations
The results show that the Langmuir isotherm is the one that best describes the adsorption process of aluminium ions on the three sorbents, with a maximum adsorption capacity of 104.17 mg g–1 for simple hydroxyapatite, 109.89 mg g–1 for hydroxyapatite synthesized in the presence of Pluronic F127 and 117.65 mg g–1 for hydroxyapatite synthesized in the presence of Pluronic P123
The sorption of aluminium (III) ions from synthetic wastewaters onto different type of hydroxyapatite has been studied as a function of contact time, the initial metal ion concentration, sorbent mass, pH, sorbent dose and temperature

Summary

Introduction

Wastewaters that contain metals are considered to be dangerous to both human and the environment due to their acute toxicity and non-biodegradability, even when the metals are present at very low concentrations. Aluminium is usually present in alum treated water, effluents from aluminium based industries and due to the salts of aluminum added to many processed foods and medicine. The main factors of the presence of aluminium in water are the industrial processes. Acid rains are the other important source for aluminium contamination of natural waters.[1,2,3]. The sources of aluminium contamination is attributed to the presence of ‘residual aluminium’ present in alum treated waters,[4,5] effluents from aluminium based industries and due to the salts of aluminium being to human health.[1,2,3,4,5] Aluminium is a neurotoxin when is added to many processed foods and medicine.[6]

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