Adsorption behavior of arsenic onto lignin-based biochar decorated with zinc

Arsenic and antimony desorption in water treatment processes: Scaling up challenges with emerging adsorbents

The metalloids arsenic (As) and antimony (Sb) belong to the pnictogen group of the periodic table; they share many characteristics, including their toxic and carcinogenic properties; and rank as high-priority pollutants in the United States and the European Union. Adsorption is one of the most effective techniques for removing both elements and desorption, for further reuse, is a part of the process to make adsorption more sustainable and feasible. This review presents the current state of knowledge on arsenic and antimony desorption from exhausted adsorbents previously used in water treatment, that has been reported in the literature. The application of different types of eluents to desorb As and Sb and their desorption performance are described. The regeneration of saturated adsorbents and adsorbate recovery techniques are outlined, including the fate of spent media and possible alternatives for waste disposal of exhausted materials. Future research directions are discussed, as well as current issues including the lack of environmental impact analysis of emerging adsorbents.

Effective adsorption of As(V) from aqueous solution by quaternary ammonium and Zn2+ decorated lignin-based sorbent

Arsenic poses a serious harm to the natural environment and human health. Lignin decorated with quaternary ammonium and metal ion can effectively adsorb arsenic from aqueous solution. Zn2+/quaternary ammonium lignin was synthesized by quaternization and metallization from lignin with 3-Chloro-2-hydroxypropyl trimethylammonium chloride and ZnCl2. The morphology, functional groups and chemical compositions of adsorbent were identified by SEM-EDS, FTIR and XRD. The effects such as pH, initial As(V) concentration, contact time and adsorbent dosage on the adsorption capacity were investigated in batch system. The adsorption mechanism was explored by SEM-EDS, FTIR and XPS. It was shown that the adsorbent was rough and contained a large amount of quaternary ammonium and Zn2+. Zn2+/quaternary ammonium lignin exhibited much strong affinity towards As(V) with the maximum adsorption capacity of 70.38 mg·g-1 at 25 °C, oscillation rate of 180 r·min-1, pH of 5, initial As(V) concentration of 100 mg·L-1, contact time of 30 min and 1 g·L-1 Zn2+/quaternary ammonium lignin. The adsorption could be well described by Langmuir model and quasi-second-order kinetic model, indicating the monolayer homogeneous chemisorption nature. As(V) was adsorbed through electrostatic attraction of Zn2+ and ion exchange between H2AsO4- and Cl-.

High efficient adsorption of W(VI) with a novel lignin-based biosorbent functionalized with Zn2+ and polyamine

Functionalized lignin-based biosorbent has become popular in wastewater treatment and extraction of valuable metals. Amination and metallization modification can effectively improve the adsorption performance of adsorbent. Zn2+/polyamine lignin for adsorption of W(VI) was synthesized by quaternization, amination and metallization from lignin with 3-chloro-2-hydroxypropyl trimethylammonium chloride, tetraethylenepentamine and ZnCl2. The adsorbent was characterized by SEM-EDS, FTIR and XRD. The adsorption performance of Zn2+/polyamine lignin for W(VI) was investigated in batch system. The adsorption mechanism was revealed by zeta potential, SEM-EDS and FTIR and XPS. It was shown that Zn2+/polyamine lignin exhibited great adsorption capacity at pH of 2, 25 °C, oscillation rate of 400 r/min, initial tungsten concentration of 700 mg·L-1 and adsorption time of 720 min. The maximum adsorption capacity of 0.5 g·L-1 Zn2+/polyamine lignin for W(VI) reached 488.28 mg·g-1. The adsorption followed Langmuir model and quasi-second-order kinetic model, indicating that the adsorption was monolayer homogeneous chemisorption. W(VI) was adsorbed through electrostatic attraction of hydrogen bond and Zn2+, ion exchange with Cl- and coordination with -NH2. The adsorption capacity reduced by only 6.47 % after seven cycles of adsorption-desorption, which indicated that Zn2+/polyamine lignin had a great application prospect.

Emerging Modification Technologies of Lignin-based Activated Carbon toward Advanced Applications

Lignin-based activated carbon (LAC) is a promising high-quality functional material due to high surface area, abundant porous structure, and various functional groups. Modification is the most important step to functionalize LAC by altering its porous and chemical properties. This Review summarizes the state-of-the-art modification technologies of LAC toward advanced applications. Promising modification approaches are reviewed to display their effects on the preparation of LAC. The multiscale changes in the porosity and the surface chemistry of LAC are fully discussed. Advanced applications are then introduced to show the potential of LAC for supercapacitor electrode, catalyst support, hydrogen storage, and carbon dioxide capture. Finally, the mechanistic structure-function relationships of LAC are elaborated. These results highlight that modification technologies play a special role in altering the properties and defining the functionalities of LAC, which could be a promising porous carbon material toward industrial applications.

Adsorption of Arsenic on Fe-Modified Biochar and Monitoring Using Spectral Induced Polarization

This work demonstrates the potential of Fe-modified biochar for the treatment of arsenic (As) simulated wastewater and the monitoring of adsorption in real-time. Specifically, we propose the utilization of date-palm leaves for the production of biochar, further modified with Fe in order to improve its adsorption function against inorganic pollutants, such as As. Both the original biochar and the Fe-modified biochar were used for adsorption of As in laboratory batch and column experiments. The monitoring of the biochar(s) performance and As treatment was also enhanced by using the spectral induced polarization (SIP) method, offering real-time monitoring, in addition to standard chemical monitoring. Both the original and the Fe-modified biochar achieved high removal rates with Fe-modified biochar achieving up to 98% removal of As compared to the 17% by sand only (control). In addition, a correlation was found between post-adsorption measurements and SIP measurements.