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.

Eco-Efficient Green Seaweed Codium decorticatum Biosorbent for Textile Dyes: Characterization, Mechanism, Recyclability, and RSM Optimization.

Biosorption using natural waste has emerged as a potential and promising strategy for removal of toxic dyes from wastewaters in comparison to conventional ones. Herein, the Codium decorticatum alga (CDA) was biologically identified and used as a biosorbent for anionic and cationic dyes from aqueous solutions. SEM analysis showed a rough surface with an irregular edge and shape while hydroxyl, amine, sulfur and carboxyl functional groups were identified using FTIR analysis. TGA/DTG confirmed the stability of CDA and the adsorption process. Batch studies were conducted to investigate the effect of operational factors such as initial pH, biosorbent dosage, temperature, initial concentration, and solid/liquid contact time on the biosorption of crystal violet (CV) and Congo red (CR) dyes. For both CV and CR dyes, the biosorption kinetics was accurately described by the pseudo-second-order model and the Langmuir isotherm was found to be best fitted for equilibrium data. Maximum uptake capacities have attained up to 278.46 mg/g for CV and 191.01 mg/g for CR. The CV and CR dye biosorption mechanism was ultimately manifested through the electrostatic interactions. The regeneration study showed that the CDA presents excellent reuse performance up to four consecutive cycles. The process optimization was performed using the response surface methodology based on Box-Behnken design (RSM-BDD). Accordingly, the optimum predicted removal efficiencies using RSM-BBD for CV and CR were obtained, respectively, at 96.9 and 89.8% using a CDA dose of 1.5 g/L, dye concentration of 20 mg/L, pH of 10 for CV, and pH of 4 for CR. Overall, CDA behaves as an efficient, recyclable, cheap, and eco-friendly adsorbent for cleaning-up of dyed effluents.

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.