Revealing the role of oxygen-containing functional groups on graphene oxide for the highly efficient adsorption of thorium ions

Effect of oxygen-containing functional group contents on sorption of lead ions by acrylate-functionalized hydrochar

The surface functional groups of hydrochar are crucial to its surface properties, and their contents are strongly positively correlated with the adsorption performance. In this study, acrylate-functionalized hydrochar (AHC) with varying contents of O-containing functional groups (OFGs) was synthesized via hydrothermal carbonization (HTC) of bamboo, acrylic acid and an initiator, and then deprotonated with NaOH. The AHCs were analyzed by various characterization techniques. During HTC, the higher amount of acrylic acid added led to higher carbon, oxygen and carboxyl contents, and to the larger specific surface area and pore volume of AHC. The adsorption kinetics, isotherms, thermodynamic, ionic strength and pH effects of Pb(II) on AHC were studied. Adsorption isotherms and kinetics obeyed Langmuir and pseudo-second-order models, respectively, indicating adsorption is monolayer chemical process. The adsorptive ability was well linearly related to the OFG contents of AHC. When acrylic acid was added to 25 mL during HTC, the adsorbing ability of AHC over Pb(II) reached 193.90 mg g-1. Hence, direct HTC of acrylic acid, biomass and an initiator can prepare hydrochar with controllable OFG contents, which is a prospective adsorbent for treating metal cations.

Insights into the Mechanism of Selective Removal of Heavy Metal Ions by the Pulsed/Direct Current Electrochemical Method

Heavy metal pollution treatment in industrial wastewater is crucial for protecting biological and environmental safety. However, the highly efficient and selective removal of heavy metal ions from multiple cations in wastewater is a significant challenge. This work proposed a pulse electrochemical method with a low-/high-voltage periodic appearance to selectively recover heavy metal ions from complex wastewater. It exhibited a higher recovery efficiency for heavy metal ions (100% for Pb2+ and Cd2+, >98% for Mn2+) than other alkali and alkaline earth metal ions (Na+, Ca2+, and Mg2+ were kept below 3.6, 1.3, and 2.6%, respectively) in the multicomponent solution. The energy consumption was only 34-77% of that of the direct current electrodeposition method. The results of characterization and experiment unveil the mechanism that the low-/high-voltage periodic appearance can significantly suppress the water-splitting reaction and break the mass-transfer limitation between heavy metal ions and electrodes. In addition, the plant study demonstrates the feasibility of treated wastewater for agricultural use, further proving the high sustainability of the method. Therefore, it provides new insights into the selective recovery of heavy metals from industrial wastewater.

Oxygen vacancy healing boosts the piezoelectricity of bone scaffolds

Although barium titanate (BaTiO3) presented tremendous potential in achieving self-powered stimulation to accelerate bone repair, pervasive oxygen vacancies restricted the full play of its piezoelectric performance. Herein, BaTiO3-GO nanoparticles were synthesized by the in situ growth of BaTiO3 on graphene oxide (GO), and subsequently introduced into poly-L-lactic acid (PLLA) powders to prepare PLLA/BaTiO3-GO scaffolds by laser additive manufacturing. During the synthesis process, CO and C-OH in GO would respectively undergo cleavage and dehydrogenation at high temperature to form negatively charged oxygen groups, which were expected to occupy positively charged oxygen vacancies in BaTiO3 and thereby inhibit the formation of oxygen vacancies. Moreover, GO could be partially reduced to reduced graphene oxide, which could act as a conductive phase to facilitate polarization charge transfer, thus further improving the piezoelectric performance. The results showed that the oxygen peak at the specific electron binding energy in O 1s declined from 54.4% to 14.6% and the Ti3+ peak that was positively correlated with oxygen vacancies apparently weakened for BaTiO3-GO, illustrating that the introduced GO significantly decreased the oxygen vacancy. As a consequence, the piezoelectric current of PLLA/BaTiO3-GO increased from 80 to 147.3 nA compared with that of PLLA/BaTiO3. The enhanced piezoelectric current effectively accelerated cell differentiation by upregulating alkaline phosphatase expression, calcium salt deposition and calcium influx. This work provides a novel insight for the design of self-powered stimulation scaffolds for bone regeneration.

CuCo2S4 Nanoparticles Embedded in Carbon Nanotube Networks as Sulfur Hosts for High Performance Lithium-Sulfur Batteries

Rational design of sulfur hosts for lithium-sulfur (Li-S) batteries is essential to address the shuttle effect and accelerate reaction kinetics. Herein, the composites of bimetallic sulfide CuCo₂S₄ loaded on carbon nanotubes (CNTs) are prepared by hydrothermal method. By regulating the loading of CuCo₂S₄ nanoparticles, it is found that when Cu²⁺ and CNT are prepared in a 10:1 ratio, the CuCo₂S₄ nanoparticles loaded on the CNT are relatively uniformly distributed, avoiding the occurrence of agglomeration, which improves the electrical conductivity and number of active sites. Through a series of electrochemical performance tests, the S/CuCo₂S₄-1/CNT presents a discharge specific capacity of 1021 mAh g^-1 at 0.2 C after 100 cycles, showing good cycling stability. Even at 1 C, the S/CuCo₂S₄-1/CNT cathode delivers a discharge capacity of 627 mAh g^-1 after 500 cycles. This study offers a promising strategy for the design of bimetallic sulfide-based sulfur hosts in Li-S batteries.