Removal of Rhodamine B from water by cedar cone: Effect of calcinations and chemical activation

Highlights

• Calcinations were carried out at temperatures between 300 and 600 °C.

• Calcinations duration times were from 30 to 5.00 h 30 min.

• Activation was carried using H₃PO₄, H₂SO₄, HNO₃, NaOH, Na₂SO₄ and Na₂CO₃, at 0.1 mol/L.

• The sorption kinetics' was found to follow the pseudo-second-order model.

• Maximum dye removal was obtained calcined cedar cone at 500 °C.

Abstract

The aim of this work is to obtain optimal preparation conditions of cedar cone (CC) using calcinations and the chemical activation. For the calcinations treatment, the temperature was varied from 300 to 600 °C at different calcinations durations (30 min–5.00 h 30 min), while the chemical activation was carried on using bases and acids reagents such as: H₃PO₄, H₂SO₄, HNO₃ for the acid reagents and NaOH, Na₂SO₄, Na₂CO₃ for bases ones successively, at the same concentration of 0.1 mol/L. Furthermore other chemical activation parameters were tested such as acids concentration and impregnation ratio. The efficiency of the treated cedar cone was tested by basic dye Rhodamine B (RhB) sorption from aqueous solutions in a batch system. The results show that the maximum dye removal was obtained for the case of calcined cedar cone at a temperature of 500 °C with a 4 h30 min time duration and for the case of HNO₃ activated cedar cone at a concentration of 2 mol/L with an impregnation ratio of 20.

The kinetic data were fitted to pseudo-first-order, pseudo-second-order, intra-particulate diffusion and Boyd models. The sorption kinetics' was found to follow the pseudo-second-order model.

Introduction

Contamination of water resources is becoming an acute problem nowadays, as a result of organic and inorganic pollutants originating from agricultural, urban and industrial activities. Dyes are broadly used in many industries such as food, paper, plastics, cosmetics and textile; in fact, textile industry ranks first in dyes usage. They represent a contaminant of concern for water resources, because of their poor biodegradability [1] and their high diffusion in aquatic environment. Their tinturial value is very high where less than 1 ppm of a dye produces obvious coloration [2]. Under these conditions, they can harm both wildlife and flora.

Among chemical and physical treatment methods, adsorption became one of the most effective methods for the removal of dyes from aqueous solutions, because of its efficiency and simplicity. Even though, activated carbon is very efficient as a sorbent, it is, however, still very expensive. Consequently, the attention was focused to search for cheaper materials. The use of non-conventional sorbent became interesting, especially when chemical or physical activation is possible. Chemical activation is a single step method of preparation of sorbents in the presence of chemical agents while physical activation involves carbonization of carbonaceous materials followed by activation of the resulting char in the presence of activating agents such as CO₂ or steam as mentioned in Ref. [3].

In this study, cedar cone, a natural material, abundant in large quantities in the forest of Chelia region, Wilaya of Khenchela, Algeria; was used as a sorbent because of its promising efficiency in the removal of a cationic dye, Rhodamine B (RhB), in a batch system as shown in a previous study [4], [5]. In order to asses the improvement of the sorption capacity of cedar cone. Calcinations and chemical activation treatment with different preparation conditions were used. The most efficient treatment is defined as the one which results in the maximal dye removal at a minimal contact time (equilibrium time). The tests of chemical activation were optimized by using different acids and bases. Since the preparation of the chemical activated sorbent can be influenced by different factors, among which reagent concentration and impregnation ratio (solid–liquid ratio). It was, therefore, necessary to evaluate the effect of these two factors in order to determine the optimal sorbent chemically activated conditions. Moreover, the study of calcinations treatment was focused on the determination of optimal temperature and calcinations duration giving the maximum dye removal percentage.