Enhanced removal of Cr(VI) using a modified environment-friendly adsorbent

Chitosan (CS) was modified by Ferric Chloride Hexahydrate (FeCl3·6H2O) and Sodium laurylsulfonate (SLS) to prepare compound adsorbent CS-Fe-SLS. Taking Cr(VI) as the target pollutant, the influence of different factors (solution pH, adsorption time, initial adsorption concentration and coexisting ions) were investigated. The results showed that the optimal pH value for Cr(VI) adsorption by CS-Fe-SLS was 3.0; The adsorption equilibrium of Cr(VI) on CS-Fe-SLS reached at 120 min, both of physical and chemical process impacted on the adsorption process; The maximum adsorption value was 131.91 mg/g, the adsorption was both single-layer adsorption and multilayer adsorption; Common co-ions such as Cl−, NO3− and SO42− had little effect on the adsorption, whereas CO32− greatly involved in the adsorption process. When Cu(II) and Cr(VI) coexisted in the solution, the adsorption strength of the adsorbent on Cr(VI) increased. The characterization results of SEM, FTIR and XRD showed that: CS-Fe-SLS and CS had different morphological characteristics. In constrast with CS, CS-Fe-SLS possessed larger volume and more flakes on the surface. SLS and Fe(III) were successfully loaded on CS. The adsorption Cr(VI) was related to -NH and -OH on the material. Some Cr(VI) were reduced to Cr(III) during the adsorption process. CS-Fe-SLS was significantly lower in crystallinity than that of CS, and was more irregular and amorphous in shape, the experimental results showed that CS-Fe-SLS had better adsorption capacity for Cr(VI).

Response Surface Optimization of Oil Removal Using Synthesized Polypyrrole-Silica Polymer Composite

The severity of oil pollution, brought about by improper management, increases daily with an increase in the exploration and usage of oil, especially with an increase in industrialization. Conventional oil treatment methods are either expensive or time consuming, hence the need for new technologies. The aim of this research is to synthesize polypyrrole-modified silica for the treatment of oily wastewater. Pyrrole was copolymerized with silica in the presence of ferric chloride hexahydrate by adding 23 mL of 117.4 g/dm3 ferric chloride hexahydrate drop wise to a silica-pyrrole mixture (1:2.3). The mixture was stirred for 24 h, filtered and dried at 60 °C for 24 h. The composite was then characterized using FTIR and SEM/EDX. A central composite model was developed in design expert software to describe the efficiency of oil removal using the polypyrrole-modified silica under the influence of initial oil concentration, adsorbent dosage and contact time. The synthesized adsorbent had FTIR bands at 3000–3500 cm−1 (due to the N-H), 1034 cm−1 (attributed to the Si-O of silica), 1607 cm−1 and 1615 cm−1 (due to the stretching vibration of C=C of pyrrole ring). The adsorption capacity values predicted by the central composite model were in good agreement with the actual experimental values, indicating that the model can be used to optimize the removal of oil from oily wastewater in the presence of polypyrrole-modified silica. The adsorbent showed excellent oil uptake when compared with similar materials. The optimum conditions for oil removal were 7091 mg/L oil concentration, 0.004 g adsorbent dosage and contact time of 16 h. Under these conditions, the percentage of oil adsorption was 99.3% and adsorption capacity was 8451 mg/g. As a result of the low optimum dosage and the lack of agitation, the material was found to be applicable in the remediation of field wastewater.

Efficient Hydrolysis of Chitin in a Deep Eutectic Solvent Synergism for Production of Chitin Nanocrystals

A deep eutectic solvent (DES) derived from ferric chloride hexahydrate and betaine chloride (molar ratio of 1:1) was used as hydrolytic media for production of chitin nanocrystals (ChNCs) with a high yield (up to 88.5%). The synergistic effect of Lewis acid and released Brønsted acid from betaine hydrochloride enabled the efficient hydrolysis of chitin for production of ChNCs coupled with ultrasonication with low energy consumption. The obtained ChNCs were with an average diameter of 10 nm and length of 268 nm, and a crystallinity of 89.2% with optimal synthesis conditions (at 100 °C for 1 h with chitin-to-DES mass ratio of 1:20). The ChNCs were further investigated as efficient emulsion stabilizers, and they resulted in stable o/w emulsions even at a high oil content of 50% with a low ChNC dosage of 1 mg/g. Therefore, a potential approach based on a DES on the production of chitin-based nanoparticles as emulsifiers is introduced.

Different Insights into Silicate Rectorite Modification and Its Role in Removal of Heavy Metal Ions from Wastewater

In the field of water management, the separation of metal contaminants from wastewater is very important and challenging. This study systematically investigated the effect and underlying mechanism of silicate rectorite (REC) on the removal of heavy metal ions (Cr(VI) and Pb(II)) from wastewater. The adsorption and removal capacity of REC was further improved by its novel modification with ferric chloride hexahydrate. Compared to natural REC, the modified rectorite (Fe-REC) showed comparatively superior adsorption efficiency for both Cr(VI) and Pb(II) due to the chemisorption of Fe3+ on the REC surface as its oxidation state (Fe–O, Fe–OH, Fe–OOH). Adsorption on Cr(VI) attributed to the reaction between iron hydroxy complexes (FeOH2+, Fe(OH)2+ and Fe(OH)3(aq)) and Cr(VI) species (HCrO4− and CrO42−) in the aqueous solution. This reaction was perfectly consistent with the binding energy shifts in O 1s and Fe 2p species, as reflected by XPS analysis. While, the existence of –Al–OH and –Si–OH in silicate REC slurry reacted with PbOH+ colloids produced from lead ions hydrolysis to promote Pb(II) adsorption. Zeta potential after modification and removal occurred to shift positively or negatively to testify the adsorption of Fe3+ and heavy metal ions. Freundlich and Langmuir isotherms conformed adsorption process for Cr(VI) and Pb(II), respectively.

Solvent-free Synthesis of 5H-dibenzo[b,i]xanthene-tetraones and Aryl-14Hdibenzo[a,j]xanthenes Using Ferric Chloride Hexahydrate as Catalyst

A simple and convenient procedure for the synthesis of 5Hdibenzo[<em>b,i</em>]xanthene-tetraones and aryl-14<em>H</em>-dibenzo[<em>a,j</em>]xanthenes is described through the condensation of aldehydes with 2-naphthol or 2-hydroxy-1, 4-naphthoquinone under solvent-free conditions in the presence of ferric chloride hexahydrate. This method has the advantages of high yields, cleaner reaction, simple work-up and cost efficiency.