Kinetic, Equilibrium and Thermodynamic Studies of Cadmium (II) Adsorption by Modified Agricultural Wastes

Abstract

Agricultural wastes have great potential for the removal of heavy metal ions from aqueous solution. The contamination of water by toxic heavy metals is a worldwide environmental problem. Unlike organic pollutants, the majority of which are susceptible to biological degradation, heavy metals do not degrade into harmless end products. Discharges containing cadmium, in particular, are strictly controlled because of the highly toxic nature of this element and its tendency to accumulate in the tissues of living organisms. This work aims to develop inexpensive, highly available, effective metal ion adsorbents from natural wastes as alternatives to existing commercial adsorbents. In particular, Tamrix articulata wastes were modified chemically by esterification with maleic acid to yield a carboxyl-rich adsorbent. The adsorption behavior of treated Tamrix articulata wastes toward cadmium ions in aqueous solutions in a batch system has been studied as a function of equilibration time, adsorbent dose, temperature and pH. Results showed that the maximum adsorption capacity was 195.5 mg/g in a pH 4 solution at 30 °C with a contact time of 120 min, an initial concentration of 400 mg/L and an adsorbent dose of 0.3 g/L. The kinetic data were analyzed using pseudo-first-order and pseudo-second-order kinetic models. It was shown that the adsorption of cadmium could be described by a pseudo-second-order equation. The experimental data were also analyzed using the Langmuir and Freundlich models of adsorption. Thermodynamic parameters such as ΔGo, ΔHo and ΔSo have been evaluated and it has been found that the sorption process was spontaneous and exothermic in nature. From all of our data, we conclude that the treated Tamrix articulata wastes investigated in this study showed good potential for cadmium removal from aqueous solutions.

Simple and facile synthesis of amino functionalized hollow core–mesoporous shell silica spheres using anionic surfactant for Pb(II), Cd(II), and Zn(II) adsorption and recovery

“…At low concentrations, the ratio of available surface to initial Pb, Cd, and Zn concentration is large, so the removal becomes independent on the initial concentration. However, in the case of higher metal cation concentrations, this ratio becomes lower and the removal percentage depends upon the initial concentration [42,43].…”

Valorization of agricultural waste into activated carbons and its adsorption characteristics for heavy metals

“…Adsorption technology is presented to be one of the most promising methods to this end [4][5][6]. Activated carbons to remove heavy metals are currently produced from a variety of starting materials such as wastes and agricultural residues [7][8][9][10][11], and polymers [12,13] and mixed solid waste [14] and rubber wood sawdust [15]. Nowadays, there is a great interest in finding inexpensive and effective alternatives to the existing commercial activated carbon [16,17].…”

Removal of Cd(II) from Aqueous Solution Using Dried Plant (Azadirachta indica) Biomass

“…Cadmium, well known for its harmful environmental impacts [12], has gained significance due to its persistence and subsequent toxicity in the ecosystem. Sources of cadmium in the environment largely include fertilizers and pesticides, cadmium batteries, smelting processes, electroplating and extensive mining activities [13,14]. Cadmium being toxic, it can be mutagenic, teratogenic as well as carcinogenic in nature [15].…”

“…Industrial effluents carry higher concentrations of heavy metals like cadmium, which can significantly harm the environmental components. Researchers have used several cost-effective/non-conventional materials as biosorbent for the removal of cadmium and other heavy metals viz., maize husk [12], agricultural waste [13], green algal biomass [14], bamboo activated carbon [15] and sugar beet pulp [16]. Neem leaf powder (NLP), a low cost potential adsorbent, has been explored for meal removal elsewhere [4,17,18].…”