Performance evaluation of surfactant modified kaolin clay in As(III) and As(V) adsorption from groundwater: adsorption kinetics, isotherms and thermodynamics

Rabelani Mudzielwana; Mugera Wilson Gitari; Patrick Ndungu

doi:10.1016/j.heliyon.2019.e02756

Performance evaluation of surfactant modified kaolin clay in As(III) and As(V) adsorption from groundwater: adsorption kinetics, isotherms and thermodynamics

Heliyon. 2019 Nov 19;5(11):e02756. doi: 10.1016/j.heliyon.2019.e02756. eCollection 2019 Nov.

Authors

Rabelani Mudzielwana¹, Mugera Wilson Gitari¹, Patrick Ndungu²

Affiliations

¹ Environmental Remediation and Nano Science Research Group, Department of Ecology and Resource Management, Thohoyandou, South Africa.
² Department of Applied Chemistry, University of Johannesburg, South Africa.

Abstract

In this paper surfactant modified kaolin clay for As(III) and As(V) was prepared by intercalating hexadecyltrimethylamonium bromide (HDTMA-Br) cationic surfactant onto the clay interlayers. Batch experiments were used to evaluate the effectiveness of surfactant modified kaolin clay towards As(III) and As(V) removal. The results revealed that adsorption of As(III) and As(V) is optimum at pH range 4-8. The maximum As(III) and As(V) adsorption capacities were found 2.33 and 2.88 mg/g, respectively after 60 min contact time. The data for adsorption of As(III) showed a better fit too pseudo first order model of reaction kinetics while the data for As(V) fitted better to pseudo second order model. The adsorption isotherm data for As(III) and As(V) fitted well to Langmuir model indicating that adsorption of both species occurred on a mono-layered surface. Adsorption thermodynamics model revealed that adsorption of As(III) and As(V) was spontaneous and exothermic. The presence of Mg²⁺ and Ca²⁺ increased As(III) and As(V) adsorption efficiency. The regeneration study showed that synthesized adsorbent can be used for up to 5 times with maximum As(III) and As(V) percentage removal of 54.2% and 62.33%, respectively achieved after 5^th cycle. Surfactant modified kaolin clay mineral showed higher adsorption capacity towards As(III) and As(V) as compared to unmodified kaolin clay mineral and competitive with other adsorbent in the literature. The results obtained from this study revealed that surfactant modified kaolin mineral is a candidate material for arsenic remediation from groundwater.

Keywords: Adsorption; Isotherms; Kaolin clay mineral; Kinetics; Physical chemistry; Surfactant; Thermodynamics.