Soil contamination and human health: recent contributions

Chromium removal from aqueous solution using bimetallic Bi0/Cu0-based nanocomposite biochar

Chromium (Cr), due to its greater contamination in aquifers and distinct eco-toxic impacts, is of greater environmental concern. This study aimed to synthesize nanocomposites of almond shells biochar (BC) with zerovalent bismuth and/or copper (Bi0/BC, Cu0/BC, and Bi0-Cu0/BC) for the removal of Cr from aqueous solution. The synthesized nanocomposites were investigated using various characterization techniques such as XRD, FTIR spectroscopy, SEM, and EDX. The Cr removal potential by the nanocomposites was explored under different Cr concentrations (25-100 mg/L), adsorbent doses (0.5-2.0 g/L), solution pH (2-8), and contact time (10-160 min). The above-mentioned advanced techniques verified successful formation of Bi0/Cu0 and their composite with BC. The synthesized nanocomposites were highly effective in the removal of Cr. The Bi0-Cu0/BC nano-biocomposites showed higher Cr removal efficiency (92%) compared to Cu0/BC (85%), Bi0/BC (76%), and BC (67%). The prepared nanocomposites led to effective Cr removal at lower Cr concentrations (25 mg/L) and acidic pH (4.0). The Cr solubility changes with pH, resulting in different degrees of Cr removal by Bi0-Cu0/BC, with Cr(VI) being more soluble and easier to adsorb at low pH levels and Cr(III) being less soluble and more difficult to adsorb at high pH levels. The experimental Cr adsorption well fitted with the Freundlich adsorption isotherm model (R2 > 0.99) and pseudo-second-order kinetic model. Among the prepared nanocomposites, the Bi0-Cu0/BC showed greater stability and reusability. It was established that the as-synthesized Bi0-Cu0/BC nano-biocomposite showed excellent adsorption potential for practical Cr removal from contaminated water.

A meta-analysis on the heavy metal uptake in Amaranthus species

Metals can accumulate in different parts of plant species in high concentrations, which gives the basis for the plant-based technology called phytoremediation. Among annual species, Amaranthus is a well-studied, potential metal accumulator genus; however, some conflicts are found among published results. Thus, we studied the metal (Cd, Cu, Fe, Ni, Pb, and Zn) accumulation potential of Amaranthus plant parts (root, stem, and leaf) by meta-analysis, furthermore, by calculation of bioaccumulation factor (BAF) values. After the extensive literature search and the calculation of relative interaction intensity (RII) values, we found significant accumulation for each metal by Amaranthus individuals growing on contaminated soils compared to plants collected from uncontaminated ones. Differences among plant parts were significant for Cu and Fe, minor for Ni, Pb, and Zn, and negligible for Cd. The BAF values indicated high accumulation in the leaf, moderate in root and stem for Cd, moderate in each plant part for Pb, and very low in each plant part for Fe, Ni, and Zn. We highlight that Amaranthus species are good prospects for metal phytoremediation projects, although, due to specific plant part-metal patterns, special attention should be paid to the harvesting practice.