Study on the coordination conduct and kinetic insights within the oxo-vanadate and organic reductive nitrogen and sulfur functionalities during the reduction coupled adsorption processes: Implications in practical applications.

Vanadium(V) is arising wastewater contaminant recently. Although bio-reduction of vanadium(V) is effective, the knowledge of electron transfer pathways and coordination nature by cellular organic functionalities is seriously lacking. Herein, the coordination conduct and kinetic modes for the reduction of V(V) by organic nitrogen and sulfur functionalities in working pHs are comprehensively investigated for the first time. The kinetics follow 3 steps; (1) diffusion of V(V) species, (2) reduction of V(V) to V(IV), and (3) adsorption of existing V species. The diffusion of V(V) is controlled by the protonated =NH2+, -SH2+, -CSH+ functional groups and oxo-vanadate speciation. The reduction of V(V) to V(IV) was efficient by -SH than =NH, -NH- , because of the higher oxidation potential of sulfur and which acted as the sole electron donor in the process. The coordination of V(V)/V(IV) species interacted with oxygen, nitrogen and sulfur atoms via parallel orientation and leads to multi-docking or single-ionic interactions, revealing the previously unrecognized track. Hence, the system tested in four types of wastewaters with different pHs and resulted the comprehensive practical applicability of the system. This study proposes a novel tactic to design an efficient V(V) wastewater treatment system by considering its water parameters.

Enhanced degradation of organic compounds through the interfacial transfer of electrons in the presence of phosphate and Nitrogen-cobalt doped graphitic carbon.

Peroxymonosulfate (PMS) has been activated for the generation of reactive oxygen species by nitrogen-doped carbonaceous material. However, the influence of phosphate on the degradation performance has not been reported. In this study, phosphate ions accelerate PMS decomposition and degradation of target organic compounds such as carbamazepine, atrazine, sulfamethoxazole, and benzoic acid. It was revealed that the physical mixture of phosphate with Co and N doped graphitic carbon (GcN/Co) demonstrates the occurrence of P C, P N, and P O - C bonds. Essentially, the graphitic N or graphitic N P increased in the presence of phosphate. This was correlated with the lower electrical transfer resistance, improved electrical conductivity, and higher electron morbidity confirmed by different electrochemical tests. Moreover, due to the strong buffering capacity of phosphate at neutral pH, bicarbonate was used to confirm the negligible influence of pH. The presence of phosphate helps to recover the scavenging effect of Cl- but has no effect on the presence of HCO3- and CO32-. Nevertheless, GcN/Co demonstrates good reusability for three reaction cycles, however, in order to maintain a high catalytic performance phosphate needs to be replenished after each cycle.

Phosphate sequestration by lanthanum-layered rare earth hydroxides through multiple mechanisms while avoiding the attenuation effect from sediment particles in lake water.

Lanthanum-based adsorbents have been used extensively to capture phosphate from wastewater. However, the attenuation effect that arises from the coexistence of sediment and humic acid is the major drawback in practical applications. The Lanthanum-layered rare earth hydroxides (LRHs)-Cl (La-LRH-Cl) was synthesized and achieved high elemental phosphorus (P) adsorption capacity (138.9 mg-P g-1) along with a fast adsorption rate (k2 = 0.0031 g mg-1·min-1) over a wide pH range while avoiding the attenuation effect that arises from the coexistence of sediment and humic acid in lake water. The La-LRH-Cl effectively captured phosphate through multiple interactions, such as the ion exchange of Cl- and phosphate, the memory effect of LRH and the inner-sphere complexation of La-P. Moreover, physical models demonstrated that the adsorption of phosphate onto La-LRH-Cl was a monolayer endothermic process, during which PO43- interacted by multi-docking via parallel orientation at 293 K and multi-ionic interactions through pure non-parallel orientation at 303 K. Hence, 1000 L of 11.08 mg-P L-1 of the acquired lake water was decontaminated by 30 g of La-LRH-Cl to 0.09 mg-P L-1 within 7 days. In addition, over ~12,125 BV of an industrial effluent containing 3.26 mg-P L-1 was treated to below USEPA's discharge limit in fixed-bed tests. It was found that the memory effect of LRH was responsible for the stable performance and reusability. Therefore, more focus should be placed on the collective role of La and LRH layered structure as a means of preventing the attenuation effect in the real water matrix.

Impact of chloride ions on activated persulfates based advanced oxidation process (AOPs): A mini review.

Chloride ion (Cl-) is ever-present in aquatic environments. Different Cl- concentration have been reported in industrial water (760 mM), surface water (<21 mM), seawater (540 mM) and groundwater (<21 mM) which could potentially accumulate into large concentrations in the sea. This mini-review examines more than 200 studies and found that Cl- ions can react with strong oxidants (SO4•-, •OH, and HSO5-) generated from persulfate activation, inducing the formation of chlorine radicals, that can either (1) directly react with organics or (2) generate chlorine radicals that can participate in the conversion of the organic substrate. Although the impact of chloride radicals have been identified as either negligible, positive, or negative (inhibitive) at different Cl- concentrations, only a few studies have considered the possible generation of chlorinated by-products. Another essential detail that is often neglected is the mutagenicity and toxicity of these products, as only a few studies have reported on the biotoxicity, AOX (adsorbable organic halogen) and the degree of mineralization of Cl- containing persulfate activated AOPs (Advanced Oxidation Process). Future studies need to consider the chemical analysis of the degradation products as well as the mutagenicity, toxicity and the biological effects pre and post-oxidation process. This evaluation will address several key issues including the properties, occurrence, and toxicity of the chlorinated products, which can significantly benefit its application in a large-scale environmental application.

Application of layered double hydroxide enriched with electron rich sulfide moieties (S2O42-) for efficient and selective removal of vanadium (V) from diverse aqueous medium.

The preparation of an adsorbent with highest efficiency, selectivity and stability is usually a challenging task. Herein, we prepared a thio functionalized layered double hydroxide (LDH) denoted as S2O4 LDH by intercalating a strong reducing agent (S2O42-) in the interlayers of trimetallic LDH and was applied to capture vanadium (V(V)) oxyanions from aqueous medium of diverse conditions. The successful preparation of the adsorbent was first confirmed using XRD, FTIR, EDX and CHS analyses. The results revealed that the modified LDH showed excellent performance at a wider pH range which can avoid the tedious work of adjusting pH in actual industrial wastewater treatment. The adsorption capacity was increased with temperature and obtained 379.55 mg/g at 323 K comparing to 112.3 mg/g at 293 K. The adsorption isotherm was better fitted to Langmuir model which suggested monolayer adsorption behavior. At lower temperature (293 K), the sorption kinetics were fitted to a pseudo-first order reaction model which implied physisorption reaction while at higher temperatures (303 and 323 K), the reaction order fitted to pseudo-second order reaction model which highlighted the chemisorption reaction mechanism. As confirmed using XRD, FTIR, EDX and XPS instrumental techniques, the dominant removal mechanism of V(V) involved ion-exchange and partial reduction reactions to nontoxic and less soluble V(IV) and V(III) species due to the low valent sulfur group and followed adsorption in S2O4 LDH. The prepared adsorbent showed very good selectivity towards V(V) in the presence of different co-existing ions both in synthetic wastewater and spiked real water samples. This novel adsorbent also exhibited high recyclability and obtained >90.0% removal of V(V) after four consecutive adsorption-desorption cycles due to the unique memory effect of the LDH. We believe that this strategy provides a new direction to find highly efficient and selective materials for capturing vanadium ions from wastewater of diverse conditions.

Interpret the elimination behaviors of lead and vanadium from the water by employing functionalized biochars in diverse environmental conditions.

Wide-ranging researches have been executed to treat groundwater from different mining areas, although complex behaviors of diverse metal ion species in the groundwater have not been illustrated clearly. This research study explored the mechanisms through which Pb(II) and V(V) are eliminated in single and binary-metal removal processes by oxygen, nitrogen, and sulfur-doped biochars also considering the kinetic and characterization techniques. The adsorption efficiency of V (V) was enhanced by oxygen-doped biochar at pH 4 with an adsorption capacity of ~70 mg/g. However, Pb (II) was rapidly removed at pH 6 with a higher adsorption capacity of ~180 mg/g by the nitrogen and sulfur-doped biochar forming PbCO3 and V(CO)6 crystals along the single-metal removal process. These results could be explained by the Hard Soft Acid Base theory. The hard Lewis acid vanadium was attracted by the hard Lewis base oxygen, and the intermediate Lewis acid lead was attracted by the intermediate and soft Lewis base nitrogen and sulfur. Besides, the removal ability of Pb(II) and V(V) in the binary-metal removal process showed a similar phenomenon for all types of biochars at pH 4 with the adsorption capacity of ~400 mg/g for Pb(II) and 175 mg/g for V(V), but the composition of vanadium species remains unclear on the surface of the biochars. Initially, H3V2O7-, H2VO4-, and HVO42- species were electrostatically attracted by the oxygen-based functionalities, then V(V) species was partially reduced to VO2+ by the oxygen, nitrogen, and sulfur functionalities in different ratios. Finally, H3V2O7-, H2VO4-, and HVO42- species produced Pb5(VO4)3Cl and Pb2V2O7 which co-precipitate with Pb(II), but VO2+ does not generate any form of precipitates. The above-explained technique supports the treatment of vanadium mining groundwater with valuable vanadinite (Pb5(VO4)3Cl) mineral.

Effect of particle sizes on the kinetics of demineralization of snail shell for chitin synthesis using acetic acid.

This study considers the kinetics of snail shells demineralization process using acetic acid. It was washed, sundried then ground into four different particle sizes. The ranges of particle sizes are 6.3-4.75 mm, 4.75-2 mm, 2 - 1 mm, and 600 -300 µm. The shells were first deproteinized with sodium hydroxide solution thereafter they were demineralized using 1.2 M acetic acid solution. Kinetics of demineralization of the snail shells was performed by XRF analysis of the chitin produced at 5, 10, 15, 20, 25, 30, and 35 min. The kinetic results show that mechanism of chitin formation from snail shell occurs through the chemical reaction controlled (CRC) model of the shrinking core model for particle sizes between 6.3 - 4.75 mm, 4.75-2 mm, and 2-1 mm particle sizes while Fluid Film Diffusion (FFD) model was observed for the smaller range of 600-300 µm particle sizes. The surface morphology and the FTIR analysis of the synthesized chitin were typical of those obtained for earlier studies.

Data on the enzymatic conversion of alkaline peroxide oxidative pretreated sugarcane bagasse for the production of fermentable sugars.

Central composite design (CCD) approach of the response surface methodology design of experiment was adopted to determine the production of fermentable sugars after enzymatic conversion of alkaline peroxide oxidative pretreated sugarcane bagasse lignocellulose. MINITAB 16 statistical software was used to design the experiments, evaluate and interpret data generated during the process. The effects of factors such as time, hydrogen peroxide concentration, and temperature on treated biomass for reducing sugars (RS) production were investigated. Operating pretreatment conditions (low-high design levels) were reaction time (6-10 h), hydrogen peroxide concentrations (1-3%v/v), and reaction temperature (60-90 °C). With the desirability of optimization of 1.000, optimal reducing sugar yield after enzymatic hydrolysis was validated to be at 100.2 °C, reaction time of 4.6 h, and hydrogen peroxide concentration of 0.3% with optimum RS yield of 153.74 mg equivalent glucose/g biomass.