Adsorption of Congo red dye in water by orange peel biochar modified with CTAB

Synthesis and Characterization of N-Doped Seaweed Biochar and Removal of Cationic Dyes

The development of functional porous carbon materials has attracted great attention in various fields. In this work, N-doped algal biochar (NABc) materials were successfully prepared by an impregnation and calcination methods using Dicyandiamide as a modifier. The specific surface area, average pore volume, and average pore diameter of NABc1%, were 693.92 m2·g-1, 0.162 cm3·g-1 and 6.76 nm, respectively. The high efficiency of NABc1% in adsorbing the cationic dyes rhodamine B and methylene blue from water may be attributed to the rich pore structure of NABc1%. The adsorption experiments show that the removal rates of rhodamine B and methylene blue by NABc1% in 90 min are 99.4 and 96.2%, respectively, which are obviously higher than those before modification. The experimental results of adsorption kinetics show that the adsorption process is more consistent with the quasi-second-order kinetic fitting equation (R 2 = 0.961, 0.998). The results of isothermal adsorption experiments show that the adsorption process is more consistent with the Langmuir equation (R 2 = 0.919, 0.916), indicating that the adsorption of rhodamine B and methylene blue by NABc1% is dominated by a monolayer adsorption process. In addition, the fitting of the intraparticle diffusion model shows that internal diffusion is not the only rate-limiting step. Hence, NABc1% has great potential for practical application as an efficient adsorbent in the field of cationic dye wastewater treatment.

Regenerable chitosan-biochar-TiO2 composite sponges for hazardous pollutants removal from water: The case of carbamazepine

Water pollution is a significant worldwide problem, and research studies in this field are still in progress to find strategies for removing pollutants from water. Among the others, adsorption process seems to exhibit several advantages, especially when biomasses are in use. This work proposes biochar from olive pomace pyrolysis for adsorbing contaminants from water, in synergistic combination with TiO2, for constituting water-stable and recyclable composite chitosan-based sponges. The photocatalyst and the biochar were embedded into the polymeric chitosan foam network. So, the employed materials were characterized from a physical and chemical point of view, revealing the nature of porous adsorbent substrates having irregular surfaces useful for sequestrating pollutants. UV-Vis spectroscopy was used to monitor the amount of pollutants in water, and the maximum adsorption capacities were calculated. Carbamazepine, was selected as a model contaminant to study the process features under different working conditions. A comparison with the removal of a textile dye was also performed to unveil the mechanism of adsorption. After the pollutant adsorption, its complete desorption was obtained, proposing a way to reuse the adsorbent material, lowering the environmental impact. An alternative to regenerate the adsorbent was also studied by exploiting the photocatalytic role of TiO2.

A critical review on biochar for the removal of toxic pollutants from water environment

As an effort to tackle some of the most pressing ecological issues we are currently experiencing, there has been an increasing interest in employing biomass-derived char products in various disciplines. Thermal combustion of biomass results in biochar production, which is a remarkably rich source of carbon. Not only does the biochar obtained by the thermochemical breakdown of biomass lower the quantity of carbon released into the environment, but it also serves as an eco-friendly substitute for activated carbon (AC) and further carbon-containing products. An overview of using biochar to remove toxic pollutants is the main subject of this article. Several techniques for producing biochar have been explored. The most popular processes for producing biochar are hydrothermal carbonization, gasification and pyrolysis. Carbonaceous materials, alkali, acid and steam are all capable of altering biochar. Depending on the environmental domains of applications, several modification techniques are chosen. The current findings on characterization and potential applications of biochar are compiled in this survey. Comprehensive discussion is given on the fundamentals regarding the formation of biochar. Process variables influencing the yield of biochar have been summarized. Several biochars' adsorption capabilities for expulsion pollutants under various operating circumstances are compiled. In the domain of developing biochar, a few suggestions for future study have been given.

Nano round polycrystalline adsorbent of chicken bones origin for Congo red dye adsorption

Nano round polycrystalline adsorbent (NRPA) of chicken bones origin was utilize as effective adsorbent in Congo red dye removal via aqueous media. The NRPA adsorbent was prepared via thermal decomposition and its structure was investigated with the aids of Transmission Electron Microscopy, Fourier Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy, Energy Dispersive X-ray Analysis (EDX), and X-ray Diffractometer (XRD). A monophasic apatite phase was confirmed from XRD investigation, while functional groups analysis showed that NRPA possessed CO32-, PO43- and OH- absorption bands. The maximum adsorption capacities derived from Langmuir isotherm is 98.216 mg g-1. From the combined values of n from Freundlich and separation factor (RL) of Langmuir models, the adsorption of CR by NRPA is favourable. Thermodynamic values of 5.280 kJ mol-1 and 16.403 kJ mol-1 K-1 were found for ΔH° and ΔS° respectively. The entire values of ΔG° which ranges from - 35.248 to - 459.68 kJ mol-1 were all negative at different temperatures. Thus, nano polycrystalline adsorbent of chicken bone origin can serve as excellent adsorbent in Congo red dye removal from waste water.

Comparison of Oil-Seed Shell Biomass-Based Biochar for the Removal of Anionic Dyes-Characterization and Adsorption Efficiency Studies

This research investigated the synthesis of biochar through the direct pyrolysis of pre-roasted sunflower seed shells (SFS) and peanut shells (PNS) and compared their application for the effective removal of textile dyes from wastewater. Biochar prepared at 900 °C (SFS900 and PNS900) showed the highest adsorption capacity, which can be attributed to the presence of higher nitrogen content and graphite-like structures. CHNS analysis revealed that PNS900 exhibited an 11.4% higher carbon content than SFS900, which enhanced the environmental stability of PNS biochar. Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses of the produced biochar indicated the degradation of cellulosic and lignin moieties. X-ray photoelectron spectroscopy (XPS) revealed a 13.8% and 22.6% increase in C-C/C=C mass concentrations in the SFS900 and PNS900, respectively, and could be attributed to the condensation of polyaromatic structures. Batch experiments for dye removal demonstrated that irrespective of dye species, PNS900 exhibited superior dye removal efficiency compared to SFS900 at similar dosages. In addition to H-bonding and electrostatic interactions, the presence of pyridinic-N and graphitic-N can play a vital role in enhancing Lewis acid-base and π-π EDA interactions. The results can provide valuable insights into the biochar-dye interaction mechanisms.