Central Composite Design Optimization of Zinc Removal from Contaminated Soil, Using Citric Acid as Biodegradable Chelant

Abstract

Citric acid (CA) was evaluated in terms of its efficiency as a biodegradable chelating agent, in removing zinc (Zn) from heavily contaminated soil, using a soil washing process. To determine preliminary ranges of variables in the washing process, single factor experiments were carried out with different CA concentrations, pH levels and washing times. Optimization of batch washing conditions followed using a response surface methodology (RSM) based central composite design (CCD) approach. CCD predicted values and experimental results showed strong agreement, with an R2 value of 0.966. Maximum removal of 92.8% occurred with a CA concentration of 167.6 mM, pH of 4.43, and washing time of 30 min as optimal variable values. A leaching column experiment followed, to examine the efficiency of the optimum conditions established by the CCD model. A comparison of two soil washing techniques indicated that the removal efficiency rate of the column experiment (85.8%) closely matching that of the batch experiment (92.8%). The methodology supporting the research experimentation for optimizing Zn removal may be useful in the design of protocols for practical engineering soil decontamination applications

Optimization of aeration enhanced surfactant soil washing for remediation of diesel-contaminated soils using response surface methodology

“…Air sparging is commonly used for in situ soil remediation to remove volatile hydrocarbons (Mousset et al, 2014a), but there is no reported work on using it in ex situ surfactant enhanced soil washing. In addition, we optimize and validate the soil washing conditions by using response surface methodology (RSM) with central composite design (CCD), which is necessary to scale up the lab-based soil washing tests, reduce cost and improve the efficiency of contaminant removal (Asadzadeh et al, 2018).…”

Optimizing adsorptive removal of malachite green and methyl orange dyes from simulated wastewater by Mn‐doped CuO‐Nanoparticles loaded on activated carbon using CCD‐RSM: Mechanism, regeneration, isotherm, kinetic, and thermodynamic studies

“…Optimum conditions play a key role in adsorption process, especially in scaled‐up applications, in order to minimize costs and maximize pollutant removal efficiency . In classical optimization, only one factor is changed at a time to measure its effect; hence, it is time‐consuming, requires many experiments and practically fails to detect the interaction effects between individual components . Response surface methodology (RSM) is a statistical technique utilized by researchers to assess simultaneously the effects of different independent factors and to attain the most suitable operating parameters for use in the adsorption process.…”

Feasibility of Chinese cabbage (Brassica bara) and lettuce (Lactuca sativa) cultivation in heavily metals−contaminated soil after washing with biodegradable chelators

“…The chelators ISA, GLDA, PASP, and GCA are biodegradable and are not toxic or are poorly toxic (Pinto et al, 2014;Jani and Hogland, 2018), but this is not the case for EDTA (Asadzadeh et al, 2018;Golmaei et al, 2018). Consequently, the formation of metalechelator complex residues in washed soils and the transformation of metals into more unstable forms could cause plants to take up metals more easily.…”

“…Soil washing with chelators (Beiyuan et al, 2018;Lestan, 2017), among the remediation techniques, is one of the few available treatments for permanently removing metals from polluted soil that has recently been highly recommended as a feasible strategy. The simplicity of this technology, its short operation time and high efficiency, make it a practical option for PTEs removal (Asadzadeh et al, 2018;Tang et al, 2017). Selecting a suitable chelator is critical to the efficiency of the washing process (Asadzadeh et al, 2018).…”

“…The simplicity of this technology, its short operation time and high efficiency, make it a practical option for PTEs removal (Asadzadeh et al, 2018;Tang et al, 2017). Selecting a suitable chelator is critical to the efficiency of the washing process (Asadzadeh et al, 2018). One of the most prevalent chelators is ethylenediaminetetraacetic acid (EDTA).…”