Adsorption of heavy metal (Cadmium) in synthetic wastewater by the natural clay as a potential adsorbent (Tangier-Tetouan-Al Hoceima – Morocco region)

Abstract

During the present study, we were able to investigate and eliminate the Cd(II) ions contained in the samples of synthetic wastewater by the adsorption technique by using the natural clay (NC), taken from the Tangier-Tetouan-Al Hoceima-Morocco region. The natural clay was characterized using X-ray diffraction (XRD) and X-ray fluorescence (FRX). Further, the cations exchange capacity (CEC) value obtained by using the natural clay is reach a maximum value of the order of 27.24 meq/100 g. Then, the optimal contact time necessary for the efficient adsorption of Cd (II) using NC is 120 min. The optimal initial concentration of the adsorption capacity is reach a maximum value of the order of 150 ppm. The elimination yield value of the heavy metal Cd(II) by using natural clay investigated is of the order of 92%. Further, the increase in the removal efficiency of Cd(II) and the decrease in the amount adsorbed, owing to the increase in the number of selective sites located at the specific surface of NC studied. Langmuir and Freundlich adsorption models again support our experimental results and NC could be used as a potential adsorbent for the eliminate of the content of Cd(II) ions contained in the synthetic wastewater.

Introduction

The presence of heavy metals in the environment, resulting from discharges of industrial wastewater, owing to considerable damage to the natural balance of the aquatic ecosystem when they exceed certain concentrations [1], [2], [3], [4], [5], [6]. Water is a very important element in nature, such as the use of the quality of water intended for consumption for all living beings [7], [8], [9], [10], [11], [12]. When, all released to the environment, they give a big problem of air, soil and water pollution. The pollution produced by metallic installations and surface treatment industries [13], [14], [15], [16]. These latters are sources of metallic elements and/or heavy metals such as copper, cobalt, zinc, lead, cadmium, mercury, arsenic, nickel, etc. [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29]. These heavy metals have a harmful impact on aquatic fauna and flora and therefore on human health [30], [31], [32], [33], [34]. They requires their elimination and/or reduction before their rejection in the receiving environments by biological treatment techniques (aerobic and anaerobic) [35], [36], physical treatments [37], [38], membrane treatments (microfiltration, ultrafiltration, reverse osmosis and nanofiltration) [39], [40], [41], [42], [43], [44], [45], [46], [47], [48] and chemical treatments (coagulation, flocculation, precipitation, adsorption,…) [49], [50], [51], [52], [53], [54]. Adsorption technique by natural clay is one of the physicochemical separation processes which finds its application with respect to several ranges of heavy metals [55], [56], whose advantage of being simple to implement, its high efficiency and its simplicity of application [57], [58]. Among the adsorbents used, there are organic adsorbents (resins) [54], [59], [60], [61], [62], [63], [64], composites and nanocomposites [65], [66], [67], [68], [69], [70], [71], [72], inorganic (shells, zeolitic, clay, activated carbon, etc.) and mineral (alumina and oxides, etc.) [9], [73], [74], [75]. The objective of our work consist to investigate and study the natural clay as a potential adsorbent to eliminate the cadmium ions contained in the samples of synthetic wastewater. X-ray diffraction and X-ray fluorescence analyzes of natural clay were realized. Further, the mass of the adsorbent, the initial concentration of cadmium, the contact time, the cations exchange capacity and the pH effect were done to evaluate the elimination yield of the heavy metal Cd(II) by using natural clay as an adsorbent in the synthetic wastewater, taken from the Tangier-Tetouan-Al Hoceima-Morocco region. The experimental data were supported by the kinetics of Langmuir and Freundlich adsorption models [76], [77], [78], [79], [80], [81], [82], [83].