Evaluation of fluoride and cadmium adsorption modification of corn stalk by aluminum trichloride

Immobilization and retention of caffeine in soil amended with Ulva reticulata biochar.

Fluoride (F-) is one of the essential elements found in soil and water released from geogenic sources and several anthropogenic activities. Fluoride causes fluorosis, dental and skeletal growth problems, teeth mottling, and neurological damage due to prolonged consumption, affecting millions worldwide. Adsorption is an extensively implemented technique in water and wastewater treatment for fluoride, with significant potential due to efficiency, cost-effectiveness, ease of operation, and reusability. This review highlights the current state of knowledge for fluoride adsorption using biochar-based materials and the limitations of biochar for fluoride-contaminated groundwater and industrial wastewater treatment. Biochar materials have shown significant adsorption capacities for fluoride under the influence of low pH, biochar dose, initial concentration, temperature, and co-existing ions. Modified biochar possesses various functional groups (-OH, -CC, -C-O, -CONH, -C-OH, X-OH), in which enhanced hydroxyl (-OH) groups onto the surface plays a significant role in fluoride adsorption via electrostatic attraction and ion exchange. Regeneration and reusability of biochar sorbents need to be performed to a greater extent to improve removal efficiency and reusability in field conditions. Furthermore, the present investigation identifies the limitations of biochar materials in treating fluoride-contaminated drinking groundwater and industrial effluents. The fluoride removal using biochar-based materials at an industrial scale for understanding the practical feasibility is yet to be documented. This review work recommend the feasibility of biochar-based materials in column studies for fluoride remediation in the future. 

State-of-the-art of research progress on adsorptive removal of fluoride-contaminated water environments using biochar-based materials: Practical feasibility through reusability and column transport studies.

The reduction of fluoride concentrations in water is one of many concerns. Adsorption is the most widely used technology for fluoride removal and the center to development of adsorption technology is the improvement of adsorbents. This review classifies the typical fluoride removal adsorbents into four types: metal oxides/hydroxides, biopolymers, carbon-based, and other adsorbents. The exploitation of new materials and the synthesis of composite materials are two ways of developing new adsorbents. In comparison to the discovery of novel adsorbents for fluoride adsorption, research into the composite synthesis of different types of conventional adsorbents has proliferated in recent years. The traditional adsorbents used the earliest, metal oxides, can act as active centers in a wide range of applications for modifying and compounding with other types of adsorbents. This study emphasizes reviewing the research on fluoride removal by composite adsorbents synthesized from different types of metal-modified materials. Seven factors were compared in terms of material characterization, initial fluoride concentration, adsorbent dose, pH, temperature, reaction time, and maximum adsorption capacity. The modification of composite adsorbents is facile and the synergistic effect of the different types of adsorbents significantly improves fluoride adsorption capacity. Metal composite adsorbents are synthesized by facile coprecipitation, hydrothermal, or impregnation modification methods. The adsorption mechanisms involve electrostatic attraction, ion exchange, complexation, and hydrogen bonding. The fluoride adsorption capacity of composite adsorbents has generally improved, indicating that most modifications are successful and have application prospects. However, to achieve significant breakthroughs in practical applications, numerous issues such as cost, separation/regeneration performance, and safety still need to be considered.

Synergistic Fluoride Adsorption by Composite Adsorbents Synthesized From Different Types of Materials—A Review

Cerium alginate cross-linking with biochar beads for fast fluoride removal over a wide pH range

The present work proposes the synthesis of robust biochar from Gracilaria Rhodophyta red weeds for sequential removal of Al(III) and fluoride from wastewater. The sorption experiments have been modeled by preliminary optimization of operational parameters using 24 factorial statistical modeling. The model has estimated an optimum sequential synergetic removal of 44.5 mg/g of Al(III) and 2.1 mg/g of fluoride onto the biochar. FESEM, BET, XRD, EDX, and FTIR established the potentiality of biochar toward synergetic sorption of Al(III) and fluoride. The thermodynamic analysis projected that the adsorption is physisorption in nature. The adsorption of Al(III) and fluoride follows the Langmuir and Freundlich isotherm models, respectively, and the kinetic analysis established the pseudo-second-order deposition of Al(III) and fluoride ions. The synthesized adsorbent is regenerative enough and could achieve synergetic removal of Al(III) and fluoride ions from industrial- and groundwater-contaminated water bodies. PRACTITIONER POINTS: Biochar from seaweeds is explored in the sequential removal of Al(III) and F- ions. Statistical model is developed for % adsorption and tested for reliability by ANOVA. GRBC sorbed 44.5 and 2.1 mg/g of Al(III) and F- ions, respectively, at optimum levels. FESEM, EDX, XRD, and FTIR characterization confirm the potentiality of the GRBC. GRBC sorbed ⁓90% of Al(III) and F- ions from wastewater and is regenerative.

Devarapu Srinivasa Reddy

Papers

Sequential synergetic sorption analysis of Gracilaria Rhodophyta biochar toward aluminum and fluoride: A statistical optimization approach.