Clay-activated carbon adsorbent obtained by activation of spent bleaching earth and its application for removing Pb(II) ion

Enhanced improvement of soda saline-alkali soil by in-situ formation of super-stable mineralization structure based on CaFe layered double hydroxide and its large-scale application

In-situ super-stable mineralization technology with mineralizers (CaSO₄, Fe₂(SO₄)₃) and attapulgite (ATP) clay were applied to improve soda saline-alkali soil. The addition of mineralizers and the existence of OH and CO₃^2- in soil resulted in the formation of CaFe-layered double hydroxide (CaFe-LDH) with super-stable mineralization structure (K_sp = 1.512 × 10^-61), which was confirmed by the characterization of physicochemical properties and density functional theory (DFT) calculation. The fixation of OH^- and CO₃^2- during the formation process of CaFe-LDH led to the transformation of the existing forms of OH^- and CO₃^2- in soil from free to stable state, resulting in the permanent decrease of soil pH and CO₃^2- concentration. The effect of ATP clay on the decrease of soluble Na ions in soil through electrostatic attraction and cation exchange was also indicated. Furthermore, mineralizers (1.2 t/ha CaSO₄ and 0.75 t/ha Fe₂(SO₄)₃) and ATP clay (1.2 t/ha) were applied to 1.33 ha soda saline-alkali land, and Rumex patientia L. was seeded meanwhile for the identification of improved performance. After five months of improvement, the physical and chemical properties of soil were improved that pH, electrical conductivity (EC), the concentration of CO₃^2- and soluble Na ions, and soil bulk density decreased significantly. In addition, the emergence rate of Rumex patientia L. increased from 0% to 98.3%. All above indicated that in-situ super-stable mineralization technology with the properties of high efficiency, long-term and cost-effective (234.88 $/ha) displays excellent potential in the improvement of soda saline-alkali soil.

Activated Bledug Kuwu’s Clay as Adsorbent Potential for Synthetic Dye Adsorption: Kinetic and Thermodynamic Studies

Bledug Kuwu is one of the geological phenomena as a mud volcano that occurs in Kuwu, Purwodadi, Grobogan, Central Java, Indonesia. The evaluation of Bledug Kuwu’s clay as one of the adsorbents for synthetic dyes has been carried out. The preparation of the adsorbent started with washing the clay with distilled water, followed by activation with a solution of hydrochloric acid (1 M) under mechanistic stirring for overnight. The C−H and O−H groups found on the clay adsorbent could attract methylene blue by dispersion forces and hydrogen bonding. Hydrocloric acid activation process for clay can increase surface area from 49 to 70 m2.g−1, meanwhile, reducing the average crystal size from 48.3 to 43.4 nm. The dye removal capacity increased from 34 to 40 mg.g−1 in corresponding to the increase of the temperature from 30 to 50 °C. The results showed that the equilibrium adsorption capacity of activated Bledug Kuwu’s clay reached 99% in an adsorption time of 20 min. The kinetic models of methylene blue adsorption onto BKC and ABKC adsorbents follow the pseudo-second order and the adsorption process is spontaneous with free energy (ΔG) as −23.519 kJ.mol−1. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).