Surface functionalized carbon microspheres for the recovery of copper ion from refinery wastewater

Preparation of molecularly imprinted polymer for the specific adsorption and selective extraction of alkylresorcinols from whole wheat flour

Alkylresorcinols are important biomarkers for evaluating whole wheat foods. However, their structures encompass a broad spectrum of homologs, making isolating and analyzing individual alkylresorcinol notably challenging. Herein, we synthesized highly selective molecularly imprinted polymers (MIPs) utilizing a facile and cost-effective precipitation polymerization method and 5-heneicosylresorcinol (ARC21:0) as the template molecule. Various crucial preparation parameters were systematically optimized, such as different porogens, functional monomers, imprinting ratios, and polymerization time. The polymers were characterized through scanning electron microscopy and Fourier transform infrared spectroscopy, and their adsorption performances were thoroughly evaluated. MIPs exhibited a notably enhanced adsorption capacity compared with that of non-imprinted polymers, reaching an optimal adsorption amount of 71.75 mg·mL-1 and imprinting factor of 2.02. Altogether, the synthesized MIPs showed superior affinity and selectivity for ARC21:0, as confirmed by their selective extraction, suggesting their potential applications in the analysis, separation, and monitoring of ARC21:0 in whole wheat foods.

Synthesis and characterization of activated carbon from sugar beet residue for the adsorption of hexavalent chromium in aqueous solutions

A series of micro–mesoporous activated carbons (ACs) were prepared from sugar beet residue by a two-step method including KOH chemical activation and were used for Cr(vi) removal from aqueous solutions. Several characterization techniques, including SEM, TEM, N₂ adsorption, XRD, FTIR, and Raman spectroscopy, were used to determine the chemical and physical characteristics of the ACs, and the adsorption properties of the ACs were tested. The results indicated that the high specific surface area of the ACs reached 2002.9 m² g⁻¹, and the micropore surface area accounts for 85% of the total area. The optimal conditions for achieving the maximum Cr(vi) adsorption capacity of 163.7 mg g⁻¹ by the ACs were activation with a KOH/carbon ratio of 3.0, an initial Cr(vi) concentration of 400 mg L⁻¹, an adsorbent dose of 2.0 g L⁻¹ and pH of 4.5. Therefore, the ACs exhibit excellent adsorption performance for removing Cr(vi) from aqueous solutions. According to an investigation of the adsorption process, the adsorption isotherm is most consistent with the Langmuir isotherm model, and the adsorption kinetics were well described by the pseudo-second-order model.

A series of micro–mesoporous activated carbons (ACs) were prepared from sugar beet residue by a two-step method including KOH chemical activation and were used for Cr(vi) removal from aqueous solutions.

Batch and continuous studies on the removal of heavy metals from aqueous solution using biosynthesised melanin-coated PVDF membranes

Heavy metals like mercury, chromium, lead and copper present in groundwater at lower concentrations cause severe health issues and can even be fatal when consumed. The biopigment/biopolymer melanin can be reaped from different sources like bacterium, fungus, and human hair. It has excellent heavy metal ion scavenging property and can be exploited for non-biological applications, substantially including water purification. In this work, melanin nanoparticles were derived from the marine bacterium Pseudomonas stutzeri and were coated onto hydrophobic polyvinylidene fluoride (PVDF) membrane as a support, for batch and continuous removal of heavy metal studies. Batch studies on the effect of pH, temperature and adsorbate dose and continuous adsorption studies on the effect of flow rate, adsorbate and adsorbent mass loadings were carried out by using biosynthesised melanin-coated PVDF membranes for the removal of Hg(II), Cr(VI), Pb(II) and Cu(II). Scanning electron microscope (SEM) images revealed the surface morphology, Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDS) deciphered the chemical characteristics of melanin-coated PVDF membranes before and after adsorption. Contact angle measurement confirmed the improvement in hydrophilicity of PVDF membrane upon coating with melanin. The maximum removal percentages of heavy metals achieved by melanin-coated PVDF membranes under batch mode operation were 87.6%, 88.45%, 91.8% and 95.8% for mercury, chromium, lead and copper, respectively optimised at 318 K and pH of 3 for chromium and 5 for other metals. However, the continuous mode of operation with a flow rate of 0.5 mL/min having 1 mg/L of heavy metal solution concentration exposed to 50 mg of melanin loading with a working volume of 200 mL showed better removal efficiencies compared with batch mode. The dynamic studies using Thomas and Yoon-Nelson models described the transient stage of the breakthrough curve and the model constants were calculated for column design and scale-up.

Activated Carbon Microsphere from Sodium Lignosulfonate for Cr(VI) Adsorption Evaluation in Wastewater Treatment

In this study, activated carbon microsphere (SLACM) was prepared from powdered sodium lignosulfonate (SL) and polystyrene by the Mannich reaction and ZnCl₂ activation, which can be used to remove Cr(VI) from the aqueous solution without adding any binder. The SLACM was characterized and the batch experiments were conducted under different initial pH values, initial concentrations, contact time durations and temperatures to investigate the adsorption performance of Cr(VI) onto SLACM. The results indicated that the SLACM surface area and average pore size were 769.37 m²/g and 2.46 nm (the mesoporous material), respectively. It was found that the reduced initial pH value, the increased temperature and initial Cr(VI) concentration were beneficial to Cr(VI) adsorption. The maximum adsorption capacity of Cr(VI) on SLACM was 227.7 mg/g at an initial pH value of 2 and the temperature of 40 °C. The adsorption of SLACM for Cr(VI) mainly occurred during the initial stages of the adsorption process. The adsorption kinetic and isotherm experimental data were thoroughly described by Elovich and Langmuir models, respectively. SL could be considered as a potential raw material for the production of activated carbon, which had a considerable potential for the Cr(VI) removal from wastewater.

Removal of chromium (VI) from water by porous carbon derived from corn straw: Influencing factors, regeneration and mechanism

Porous carbon is one of the most widely used materials to remove Cr(VI) from polluted water. Here we reported one efficient porous carbon material prepared from corn straw. The results of Fourier transform infrared spectroscopy (FTIR), Energy dispersion spectrum (EDS), and X-ray photoelectron spectroscopy (XPS) indicated that the porous carbon surface had functional groups such as COOH, OH and COC, etc, which could be acted as active sites during the adsorption process. Brunauer-Emmett-Teller (BET) results showed that the surface area and total pore volume of the adsorbent were 2131.181 m²/g and 1.128 cm³/g, respectively. The percentages of micropore surface area and micropore volume achieved 91.93% and 80.43%, respectively. The maximum adsorption capacity of Cr(VI) was 175.44 mg/g at 25 °C with the well-developed microporous structure and abundant oxygen-containing functional groups of porous carbon. The adsorption process was well described by the pseudo-second order model and Langmuir adsorption isotherm model. It was mainly based on chemical adsorption of a single molecular layer, accompanied by ion exchange reaction, Cr(VI) reduction, and complexation, etc. The adsorbent exhibited excellent removal performance of Cr(VI) in the co-existing ions wastewater and electroplating wastewater, and could remain high removal performance for four adsorption-desorption cycles.