A Review of the Distribution Coefficient (<i>K<sub>d</sub></i>) of Some Selected Heavy Metals over the Last Decade (2012-2021)

Abstract

This review synthesizes the methods for estimating the distribution coefficient (K d ) and provides a compilation of K d values for five heavy metals (As, Pb, Cd, Cu, and Zn) based on research published in the last decade (2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020)(2021). We used the PRISMA method to ensure the transparency of the collected data. For mono-metal systems (MS), the K d values ranged from 10 −2 to 10 7 L/kg for Pb, from 10 −2 to 10 6 L/kg for Cd, As, and Zn, and from 10 −2 to 10 5 L/kg for Cu. In competitive systems (CS), the K d values ranged from 10 −2 to 10 5 L/kg for Cu, and 10 −2 to 10 4 L/kg for Pb, Cd, and Zn, while no K d value for As was reported under CS. It was found that the K d values of heavy metals are affected not only by soil chemical and physical properties but also by the nature and characteristics of the metal involved along with experimental conditions. The totals references number of K d data observation per element metal are represented as follows: Cd 35 (50%), Zn 35 (50%), Pb 33 (47.14%), Cu 33 (47.14%), and As 19 (27.14%). Overall, most research was done 1) on MS rather than CS, 2) on sorption rather than desorption, 3) on soil rather than sediments , and 4) most literature have reported the K d values, derived from batch method than on column method. Despite significant progress over the past decade towards a better understanding of the variation in K d values and the effect of factors influencing them to provide important parameters for predicting and controlling toxic metals in soils, additional research is still warranted to the complexity of underlying processes.

Effects of Selected Properties of Semi-Arid Soil of Dutse, Jigawa State on Adsorption of Pb and Cd Ions

“…These positive correlations obtained from the relationships could be due to the formation of complexes (inner and outer) by the heavy metals with organic components in the soil largely due to the chelating effects of its functional groups. The result obtained in this study is consistent with the reports of Elbana et al (2018) and Seidou et al (2022), which found that organic matter in soils showed strong sorption with heavy metals. The R value (0.68) obtained also largely reflected the quantity of organic matter content in the study soil, which was low, as shown in Table 1.…”

Evaluation of the Phytoremediation Potential of the Sinapis alba Plant Using Extractable Metal Concentrations

“…They influence the kinetics of sorption-desorption reactions, the metal concentration in the extraction solution, and the form of soluble or insoluble chemical species [11]. The assessment and prediction of toxic metals in soil requires knowledge of their distribution in the solid-liquid system, expressed by the distribution coefficient Kd [12][13][14][15]. The Kd value of metal indicates the effect of various reactions in the solid and liquid phases.…”