Simultaneous adsorption of toxic metals in binary systems using peanut and sheanut shells biochars

Effect of biochar and iron ore tailing waste amendments on cadmium bioavailability in a soil and peanut seedling system

Biochar and iron ore tailing waste have been widely separately applied for remediation of various contaminants, but the remediation effect of their combination on cadmium (Cd) pollution is unclear. In this study, the peanut biochar (BC), thermally activated iron ore tailing waste (TS), and the products of the co-pyrolysis of peanut shell and iron ore tailing waste (TSBC) were prepared for stabilizing Cd and reducing its bio-accessibility in soil and peanut seedling system. Present amendments enhanced soil pH, cation exchange capacity, electrical conductivity, and organic carbon content. The application of BC, TS, and TSBC led to decreases in acid-extractable Cd proportion of 2.2-8.81%, 2.43-7.20%, and 7.84-11.57%, respectively, and increases in the residual Cd proportion of 3.48-8.33%, 3.27-11.50%, and 9.02-13.45%, respectively. There were no significant differences in Cd accumulation in peanut roots due to three amendments treatments, especially at low Cd concentrations (i.e., Cd concentration of 0, 1, and 2 mg·kg-1), and with a relatively small reduction (2.16-9.05%) in root Cd accumulation under the high Cd treatments of 5 and 10 mg·kg-1. The Cd concentrations in seedling roots were significantly positively related to the acid-extractable Cd fraction, with a Pearson correlation coefficient of r = 0.999. The maximum toxicity mitigating effects were found in TSBC treatment, with increases in the ranges of 9.80-17.58% for fresh weight, 5.59-14.99% for dry weight, 5.16-10.17% for plant height, 5.96-10.34% for root length, 5.43-21.67% for chlorophyll a content, 17.17-71.28% for chlorophyll b content, and 13.11-39.60% for carotenoid content in peanut seedlings. Therefore, TSBC is a promising amendment for minimizing Cd contamination in peanut crops and utilizing industrial solid waste materials efficiently.

Preparation of a biochar-lignosulfonate composite material and its adsorption performance for Cu2

Biochar was prepared using peanut shells as raw materials, and then composite amino-functionalized lignosulfonate was used to prepare a biochar/lignosulfonate adsorbent (BC-CLS). The morphology and structure of BC-CLS were characterized using FT-IR, SEM, zeta potential, and XPS. The adsorption performance of BC-CLS was evaluated by batch adsorption experiments and dynamic adsorption experiments (adsorption column flow adsorption). The results showed that BC-CLS adsorbent exhibited significant adsorption performance for Cu2+, including a short equilibrium time (50 min), fast adsorption rate (11 mg g-1 min-1), and high static saturation adsorption capacity (354 mg g-1). Dynamic adsorption experiments indicated that the maximum adsorption capacity of BC-CLS adsorbent was approximately 280 mg g-1, with a removal rate of over 99% after five cycles, meeting the wastewater discharge standard (less than 1 mg L-1). The results demonstrated that the adsorption capacity of BC-CLS adsorbent for Cu2+ was controlled by multiple adsorption mechanisms, including electrostatic attraction, precipitation, and metal ion complexation. Additionally, under pH = 5 conditions, using a 40 mg per L Cu2+ solution, the adsorption performance of BC-CLS adsorbent remained above 60% after five adsorption-desorption experiments, indicating good cycling stability of BC-CLS adsorbent.

Effective adsorption of cadmium and nickel ions in mono and bicomponent systems using eco-friendly adsorbents prepared from peanut shells

The work investigates the potential of peanut shells, an abundant agro-industrial waste, to serve as an adsorbent precursor for the effective and simple treatment of effluents loaded with cadmium and nickel ions. Among the adsorbents prepared, carbonized peanut shell (CCarb), due to its higher adsorption capacity, proved to be the most effective compared to carbonized and activated peanut shell (CATQ). The carbonization process led to structural changes, which resulted in an increase in surface area (around 6 times more in CATQ) and pore volume (around 3 times more in CATQ). Even so, the amount of H+ acid sites due to acid activation produced unfavorable effects for adsorption. Hydroxyl, carboxyl and carbonyl groups were identified on the adsorbent surface which presented favorable charges for metal adsorption. This improvement propels the carbonized variant to the forefront, demonstrating the highest adsorption capacity and reaching equilibrium in less than 90 and 60 min for cadmium and nickel ions, respectively. In both monocomponent and bicomponent systems concentrations greater than 40 ppm signify an increase in adsorption capacity for Ni2+. The experimental data best fit the Freundlich model, showing maximum adsorption capacities of 17.04 mg g-1 for cadmium and 31.28 mg g-1 for nickel. Despite the antagonistic effect observed in the bicomponent system, this study concludes by underlining the promise of activated carbon from peanut shells to harmonize technical and environmental concerns.

A Review on Remediation of Iron Ore Mine Tailings via Organic Amendments Coupled with Phytoremediation

Mining operations degrade natural ecosystems by generating a large quantity of mine tailings. Mine tailings remain in dams/open ponds without further treatment after valuable metals such as iron ore have been extracted. Therefore, rehabilitation of tailings to mitigate the negative environmental impacts is of the utmost necessity. This review compares existing physical, chemical and amendment-assisted phytoremediation methods in the rehabilitation of mine tailings from the perspective of cost, reliability and durability. After review and discussion, it is concluded that amendment-assisted phytoremediation has received comparatively great attention; however, the selection of an appropriate phytoremediator is the critical step in the process. Moreover, the efficiency of phytoremediation is solely dependent on the amendment type and rate. Further, the application of advanced plant improvement technologies, such as genetically engineered plants produced for this purpose, would be an alternative solution. Further research is needed to determine the suitability of this method for the particular environment.