Adsorption of Copper (II) Ions onto Surfactant-Modified Oil Palm Leaf Powder

Adsorption of chromium, copper, lead and mercury ions from aqueous solution using bio and nano adsorbents: A review of recent trends in the application of AC, BC, nZVI and MXene

Recent trends in adsorption of Chromium (Cr), Copper (Cu), Lead (Pb) and Mercury (Hg) in wastewater using (i) carbonaceous materials including activated carbon (AC) and biochar (BC), and (ii) nanomaterials including nano zero-valent iron (nZVI) and MXenes have been discussed in this paper. It has been found that adsorption capacity depends largely on the adsorbent modification technique, initial pH of wastewater, dosage of adsorbent, contact time and initial concentration of the pollutants. The pH value ranges for maximum removal of Cr, Cu, Pb and Hg have been reported as 2-4, 5-6, 5-8 and 3-8, respectively. Up to 99% removal of metals has been reported using AC, BC, nZVI and MXene. The mechanism involves the reduction and chemical adsorption of metals. AC and BC have a higher surface area (up to 5000 m²/g) compared to nZVI (up to 500 m²/g) and MXene (up to 67.66 m²/g). However, the higher reactivity and regeneration capacity of nZVI and MXene make them suitable adsorbents. From a practical point of view the application of adsorbents for real effluents, cost analysis, regeneration capability and reuse of heavy metals are some aspects that need attention in future studies. The removal efficiencies of AC and BC are comparable to the nZVI and MXene. The cost analysis may be an attractive aspect to decide the future application of these adsorbents at large scale.

Kinetics, Thermodynamics, and Isotherms of Methylene Blue Adsorption Study onto Cassava Stem Activated Carbon

Water treatment using activated carbon is widely accepted, despite its high production cost. Therefore, this study was aimed to investigate the potential of cassava stem in activated carbon form for methylene blue (MB) dye uptake from water. Raw cassava stem (RCS) was also utilized to evaluate the difference between cassava stem in its raw form and after being converted to the activated carbon (ACS). The MB adsorption from water using the RCS and ACS was done in this study. The batch adsorption study showed fast MB uptake by ACS at 60 min contact time, while higher adsorbent dosage and higher pH contributed to higher adsorption percentage. The thermodynamic study showed positive values of ∆H° of ACS, indicating that the adsorption process of MB was endothermic. Meanwhile, the negative value of ∆G° showed that the adsorption processes of MB were spontaneous. The thermodynamic study showed higher fitting to Langmuir isotherm, with data from the kinetic study showing better pseudo-second-order equation fitting, which suggests the chemisorption process had happened. The highest adsorption recorded by ACS was 384.61 mg/g, indicating the possibility of cassava stem as the lower cost raw material for activated carbon production with excellent adsorption characteristics.

Restoration of heavy metal-contaminated soil and water through biosorbents: A review of current understanding and future challenges

Heavy metal pollution in soil and water is a potential threat to human health as it renders food quality substandard. Different biosorbents such as microbial and agricultural biomass have been exploited for heavy metal immobilization in soil and sorptive removal in waters. Biosorption is an effective and sustainable method for heavy metal removal in soil and water, but the inherent challenges are to find cheap, selective, robust, and cost-effective bioadsorbents. Microbial and agricultural biomass and their modified forms such as nanocomposites and carbonaceous materials (viz., biochar, nanobiochar, biocarbon), might be useful for sequestration of heavy metals in soil via adsorption, ion exchange, complexation, precipitation, and enzymatic transformation mechanisms. In this review, potential biosorbents and their metal removal capacity in soil and water are discussed. The microbial adsorbents and modified composites of agricultural biomasses show improved performance, stability, reusability, and effectively immobilize heavy metals from soil and water. In the future, researchers may consider the modified composites, encapsulated biosorbents for soil and water remediation.