In Situ One-Pot Synthesis of C-Decorated and Cl-Doped Sea-Urchin-like Rutile Titanium Dioxide with Highly Efficient Visible-Light Photocatalytic Activity.

Titanium dioxide (TiO2) that offers high light-harvesting capacity and efficient charge separation holds great promise in photocatalysis. In this work, an in situ one-pot hydrothermal synthesis was explored to prepare a C-decorated and Cl-doped sea-urchin-like rutile TiO2 (Cl-TiO2/C). The growth of sea-urchin-like 3D hierarchical nanostructures was governed by a mechanism of nucleation and nuclei growth-dissolution-recrystallization growth from time-dependent morphology evolution. The crystal morphology and the content of Cl and C could be controlled by the volume ratio of HCl to TBOT. Systematic studies indicated that the 0.4Cl-TiO2/C sample (the volume ratio of HCl to TBOT was 0.4) exhibited the highest visible-light photocatalytic activity for the degradation of rhodamine B, with kinetic rate constant (k) of 0.0221 min-1, being 6.5 and 3.75 times higher than that of TiO2 and Cl-TiO2. The enhanced photocatalytic performance could be attributed to the high charge separation and transfer efficiency induced by Cl-doping and C decoration and the excellent light-harvesting capacity caused by its sea-urchin-like nanostructure. Moreover, the 0.4Cl-TiO2/C sample exhibited good reusability and excellent structural stability for five cycles. This facile one-pot approach provides new insight for the preparation of a TiO2-based photocatalyst with excellent photocatalytic performance for potential application in practical wastewater treatment.

Enhancement of hydrothermal carbonization of chitin by combined pretreatment of mechanical activation and FeCl3.

In this work, a combined mechanical activation and FeCl3 (MA + FeCl3) method was applied to pretreat chitin to enhance the degree of hydrothermal carbonization. MA + FeCl3 pretreatment significantly disrupt the crystalline region of chitin and Fe3+ entered into the molecular chain, resulting in the destruction of the stable structure of chitin. The chemical and structural properties of hydrochars were characterized by EA, SEM, FTIR, XRD, XPS, 13C solid state NMR, and N2 adsorption-desorption analyses. The results showed that the H/C and O/C atomic ratios of HC-MAFCT/230 (the hydrochar derived from MA + FeCl3 pretreated chitin with hydrothermal reaction temperature of 230 °C) were 0.96 and 0.34, respectively. Van Krevelen diagram indicated that the hydrothermal carbonization of chitin underwent a series of reactions such as dehydration, decarboxylation, and aromatization. HC-MAFCT/230 had abundant oxygen- and nitrogen-containing functional groups. HC-MAFCT/230 exhibited a porous structure, with the specific surface area of 128 m2 g-1, which was a promising carbon material.

Formation of type 3 resistant starch from mechanical activation-damaged high-amylose maize starch by a high-solid method.

This study focused on constructing a high-solid reaction system to prepare type 3 resistant starch (RS3) with high-amylose maize starch as raw material by mechanical activation (MA) pretreatment combined with thermal and freeze-thaw treatments. MA pretreatment effectively destroyed the crystal structure and molecular structure of native starch. MA damaged starch with a certain viscosity could form dough with a small amount of water to construct a starch continuous phase system. RS content increased with the damage levels of starch as the formation of double helix structure, attributed to that the molecules of MA damaged starch could be easy to move and form recrystallization structure. Thermal and freeze-thaw treatments contributed to strong interaction of starch-water and the re-formation of internal crystal structure of MA damaged starch to form RS3. This study provides insight into the development of a highly effective approach for large scale production of resistant starch.

Synthesis of starch-based super absorbent polymer with high agglomeration and wettability for applying in road dust suppression.

Dust pollution is an important factor restricting social development and affecting human health, especially in some developing countries. Herein, mechanical activation-assisted solid phase reaction (MASPR) and conventional liquid phase (LP) method were employed to synthesize different superabsorbent polymers (SAPs), defined as SAP-MA and SAP-LP, respectively. The rheological properties, crystal structure, changes of functional groups, and dust suppression performance of the SAPs prepared by these two methods were compared, and the dust suppression mechanism of SAPs was discussed via the adsorption experiment between dust suppressant and dust particles. The results showed that SAPs were successfully prepared by the two methods. Compared with SAP-LP, SAP-MA with lower molecular weight, higher grafting rate, and better fluidity and water absorption showed excellent suppression performance. This enhancement could be attributed to that the SAP-MA exhibited lower crystallinity and better film-forming ability, anti-evaporation, anti-consolidation, and permeability induced by MA. Furthermore, the effective chemical adsorption between SAPs and dust particles had a stable consolidation effect. This environmentally-friendly method for the preparation of starch-based super absorbent polymer for road dust suppressant may provide new insights for the valorization of cassava starch and large-scale production of dust suppressant.

Effective treatment and utilization of hazardous waste sulfuric acid generated from alkylation by lignocellulose ester-catalyzed oxidative degradation of organic pollutants.

Alkylation reaction catalyzed by concentrated H2SO4 generates hazardous waste H2SO4 containing a large amount of organic pollutants. This study focused on effective utilization and treatment of the waste H2SO4 for simultaneous consumption of H2SO4 and deep oxidative degradation of the organics. The waste H2SO4 could completely react with magnesium oxide ore to prepare crude MgSO4 solution, and the organic pollutants in the solution were deeply degraded and mainly mineralized to H2O and CO2 with H2O2 as oxidant and sugarcane bagasse citrate (SBC), a kind of lignocellulose ester, as catalyst. The total amount of acidic groups of SBC significantly affected its catalytic activity, attributing to that these oxygen-containing functional groups adsorbed and immobilized metal ions on SBC to form catalytic active sites, which could activate and catalyze H2O2 to generate •OH and HO2• radicals for effective degradation of the organics. The resulting purified MgSO4 solution with color removal of 93.71% and total organic carbon removal of 85.89% under optimum catalytic reaction conditions was used to produce qualified MgSO4∙7H2O product. These results highlighted the feasibility of using lignocellulose ester as effective catalyst for deep oxidative degradation of hazardous organic pollutants.

Preparation of a Stable Nanoscale Manganese Residue-Derived FeS@Starch-Derived Carbon Composite for the Adsorption of Safranine T.

To develop a novel, low-cost adsorbent with natural material and industrial waste as raw materials, nanoscale manganese residue-derived FeS@starch-derived carbon (MR-FeS@SC) composite was prepared by the carbonization of starch-manganese residue gel. Manganese residue-derived FeS (MR-FeS) and starch-derived carbon (SC) were also prepared as contrasts for comparative studies. The MR-FeS@SC nanocomposite exhibited relatively large specific surface area and micropore volume, appropriate pore size, abundant functional groups, strong interaction between the functional groups of SC and MR-FeS, and the immobilization and uniform distribution of MR-FeS nanoparticles onto SC support material, which contributed to better adsorption properties for the removal of Safranine T (ST) from the aqueous solution compared with those of MR-FeS and SC. The adsorption could be conducted at a wide range of pH and temperature to achieve a satisfy removal efficiency of ST with MR-FeS@SC nanocomposite as adsorbent. The adsorption kinetics well followed the pseudo-second-order model, and the dominant mechanism was chemisorption. The adsorption behavior was well described by the Langmuir isotherm model. Due to the strong interaction between MR-FeS nanoparticles and SC support, MR-FeS@SC nanocomposite exhibited better reusability and stability even after fifteen cycles. This study provides a facile method of preparing effective and stable adsorbents for the treatment of dye wastewater.

Mineralization of organics in hazardous waste sulfuric acid by natural manganese oxide ore and a combined MnO2/activated carbon treatment to produce qualified manganese sulfate.

To effectively dispose and utilize the hazardous waste H2SO4 generated from alkylation, an environmentally friendly and feasible technology for the simultaneous oxidative degradation of organics and consumption of H2SO4 was developed. Pyrolusite, a natural manganese oxide ore, was used for the oxidative degradation and mineralization of the organics, and reduction leaching of Mn from the pyrolusite occurred simultaneously. The total organic carbon (TOC) removal and Mn leaching efficiency were 46% and 16.44%, respectively. In addition, pyrites was applied as a reductant to extract Mn from the pyrolusite, and an Mn leaching efficiency of 98.31% was obtained under the optimized conditions of 4/1 liquid/solid ratio, 350 rpm stirring speed, 1.5 mol L-1 H2SO4 concentration, and 95 °C for 1 h in the first oxidative degradation stage and a molar ratio of FeS2/MnO2 of 0.55/1 for 4 h in the reduction leaching stage. Subsequently, a combined treatment of MnO2/activated carbon was developed for further oxidation and adsorption of the organics in the solution, with the TOC removal of 84.11%. The resulting purified MnSO4 solution was concentrated to produce qualified MnSO4∙H2O, which met the requirements of an industrial product. This technology showed application potential in highly-efficient removal of hazardous organic contaminates.