Novel citric acid-functionalized brown algae with a high removal efficiency of crystal violet dye from colored wastewaters: insights into equilibrium, adsorption mechanism, and reusability.

Synthetic dye waste is one of the world's key ecological concerns. The algal biomass has emerged as a promising alternative adsorbent for wastewater treatment. The present study deals with the functionalization of brown algae (BA) by citric acid in order to improve its adsorption ability for textile dye removal in aqueous solutions. The morphological texture (SEM and BET) and surface chemistry (FTIR, EDS-mapping, and PZC) of the novel functionalized brown algae (designated as BA-CA) were analyzed. The performance of BA-CA for crystal violet (CV) dye removal from wastewater was investigated. The isotherm and kinetic adsorption modeling indicate the good fit of Langmuir isotherm and pseudo-second-order models. Optimum monolayer uptake capacity was 279.14 mg/g for BA-CA, which was about two times higher than that of unmodified BA. The thermodynamic parameters clearly indicated that CV removal process was physiosorption, exothermic, and spontaneous in nature. The regeneration study showed excellent reusability of the BA-CA up to five cycles. Overall, the experimental findings lead us to conclude that the BA-CA can be used as an eco-friendly, cost-effective and easily regenerated adsorbent for the purification of textile effluents.

Elaboration of novel polyaniline@Almond shell biocomposite for effective removal of hexavalent chromium ions and Orange G dye from aqueous solutions.

A novel polyaniline@Almond shell (PANI@AS) biocomposite was synthesized via facile in situ chemical polymerization method. The as-synthesized adsorbent was characterized using various analytical techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and potentiometric titration. A batch adsorption system was applied with the aim of investigating as-synthesized adsorbent ability to remove Cr(VI) ions and Orange G (OG) textile dye from aqueous solutions. Obtained results revealed that adsorption process was strongly depended upon the physicochemical parameters. The adsorption of Cr(VI) and OG dye onto PANI@AS was better described by the pseudo second-order-kinetic model and followed the Freundlich isotherm model. The maximum uptakes were 335.25 for Cr(VI) and 190.98 mg g-1 for OG dye. We further evaluated that PANI@AS biocomposite could be regenerated easily with NaOH solution and efficiently reused for Cr(VI) and OG dye removal from aqueous media. Thus, these results indicated the potential practical application of PANI@AS biocomposite for wastewater treatment.

Efficient removal of p-nitrophenol from water using montmorillonite clay: insights into the adsorption mechanism, process optimization, and regeneration.

The present research highlights the use of a montmorillonite clay to remove p-nitrophenol (PNP) from aqueous solution. The montmorillonite clay was characterized using powder X-ray diffraction, Fourier-transformed infrared spectroscopy, scanning electron microscopy, X-ray fluorescence, Brunauer-Emmett-Teller analyses, and zero point charge in order to establish the adsorption behavior-properties relationship. The physiochemical parameters like pH, initial PNP concentration, and adsorbent dose as well as their binary interaction effects on the PNP adsorption yield were statistically optimized using response surface methodology. As a result, 99.5% removal of PNP was obtained under the optimal conditions of pH 2, adsorbent dose of 2 g/l, and PNP concentration of 20 mg/l. The interaction between adsorbent dose and initial concentration was the most influencing interaction on the PNP removal efficiency. The mass transfer of PNP at the solution/adsorbent interface was described using pseudo-first-order and intraparticle diffusion. Langmuir isotherm well fitted the experimental equilibrium data with a satisfactory maximum adsorption capacity of 122.09 mg/g. The PNP adsorption process was thermodynamically spontaneous and endothermic. The regeneration study showed that the montmorillonite clay exhibited an excellent recycling capability. Overall, the montmorillonite clay is very attractive as an efficient, low-cost, eco-friendly, and recyclable adsorbent for the remediation of hazardous phenolic compounds in industrial effluents.