Adsorption capability of brewed tea waste in waters containing toxic lead(II), cadmium (II), nickel (II), and zinc(II) heavy metal ions

Hakan Çelebi,Gülden Gök,Oğuzhan Gök

doi:10.1038/s41598-020-74553-4

Abstract

Recently, the search for low-cost eco-friendly adsorbents has become one of the main objectives of researchers. The aim of this study was to test the removal of four heavy metals, namely lead (Pb), zinc (Zn), nickel (Ni) and cadmium (Cd), from a simulated watery solution using brewed tea waste as a potentially suitable adsorbent. The effects of pH levels (2.0–6.0), adsorbent amount (0.1–5.0 g), contact times (1–150 min.) were examined throughout the adsorption process. The results of the experiments showed that the heavy metals elimination yields had an inverse relationship with pH and a linear relationship between the other parameters. The optimum pH for the removal of the heavy metals was between 4.0 and 5.0 in the case of the brewed tea waste. Equilibrium times of 2, 10, 30 and 5 min were required for the adsorption of Pb, Zn, Ni, Cd onto Camellia sinensis, respectively. Based on the results of this study it can be said that brewed tea waste has a high potential to remove heavy metals from aqueous solutions. The maximum adsorption capacities were calculated as 1.197, 1.457, 1.163 and 2.468 mg/g, for Pb, Zn, Ni and Cd, respectively, by fitting the equilibrium data to the Langmuir isotherm model.

Highlights

The discharge of heavy metals and other toxic pollutants into waterways is one of the most significant and frequent detrimental effects of industrial activities that causes water pollution[1]
As the Brewed tea waste (BTW) was used as an adsorbent, its adsorption capacity was negatively affected by the structure of its surface in addition to other mechanisms that played important roles in the rate of adsorption
The values of the Langmuir isotherm in this study indicated a positive interaction between the adsorbate and the BTW, which is valid proof of an ion-exchange mechanism taking place throughout the adsorption process (Table 4)

Summary

Introduction

The discharge of heavy metals and other toxic pollutants into waterways is one of the most significant and frequent detrimental effects of industrial activities that causes water pollution[1]. As a result of the development of important sectors such as agriculture, battery production, metal plating the discharge of heavy metals into the environment has increased both directly and indirectly Hazardous heavy metals such as Cd, Pb, Zn and Ni in particular are used extensively in these sectors and cause significant problems in water and other receiving environments. The removal of heavy metal ions from waters using tea waste is essentially a threestep process: (i) adsorption, (ii) surface precipitation, and (iii) fixation[24]. The main species present at pH ≤ 6 are Pb2+, Ni2+-Ni2H, Zn2+, Cd2+-CdOH+, while at pH ≥ 7 they are Pb(OH)2-PbO2, NiOH+, Zn(OH)2-ZnO22−, and Cd(OH)2-CdO22–18,21–26 The occurrence of these surface complexes, creating a three-dimensional phase during the removal of heavy metals from a medium by using tea wastes, can be described as surface precipitation. The main purpose of this study was to help scientists select suitable adsorbents for the removal of target heavy metals and facilitate the development of new adsorbents

Objectives

Methods

Results

Conclusion