Low-temperature Solid-phase Synthesis Of InVO₄Used For Dyes Removal In Wastewater And The Shape-controlled Hydrothermal Synthesis Of InPO₄

In this paper, a new solid phase method at low-temperature had been used to prepare the InVO4.X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and UV-visible diffusereflectance spectroscopy (DRS) techniques were used to characterize the product. The resultsshowed that:(a) by changing the grinding time, reaction time and reaction temperature, theoptimum conditions for the synthesis of the orthorhombic InVO4can be obtained.(2) by addingdifferent surfactants, monoclinic InVO4can be obtained, then the obtained monoclinic phaseInVO4was heated with suitable temperature, orthorhombic InVO4can be obtained.(3) when theraw material grinding with adding different surfactants, and then heated with suitable temperature,InVO4with different morphologies can be obtained. We considered the methylene blue dye as andegradation of object and compared the photocatalytic effect of InVO4with these morphologies.The results showed that photocatalytic activity of InVO4with spherical morphology under visiblelight can reach the most highest degradation rate of methylene blue, was78.68%in120min.Meanwhile,the InVO4was prepared by mixed the raw materials, and then the mixed material wasmilled for30min,finally, the precursor was heated at140C for12h. A study on the removal ofmethylene blue (MB) and neutral red (NR) from aqueous solutions by InVO4was conducted underbatch conditions. The effects of dosage, initial solution pH, salt concentration, contact time, initialconcentration and temperature on the adsorption were investigated in detail. The adsorption ofdyes was a fast process that followed the pseudo-second-order kinetics. This process could bedescribed by the Langmuir model and gave the maximum adsorption capacity of196.43and209.92mg/g respectively for MB and NR, which was superior to most of adsorbents in literature.The negative change in free energy (ΔG) and positive change in enthalpy (ΔH) indicated that theadsorption was a spontaneous and endothermic process. The removal efficiencies were found tovary with dosage, contact time, initial concentration and temperature. But the adsorption wasalmost independent on pH value, and slightly influenced by ionic strength. All the resultsindicated that InVO4was able to be utilized as a potential effective dye adsorbent for practicalapplication.Orthorhombic InPO4crystals with different morphologies were synthesized by controllingtemperature and pH via a mild additive-free hydrothermal method. The effects of temperature andpH on the structures and morphologies of the products were investigated. The as-prepared samples were well determined by X-ray diffraction (XRD) and scanning electron microscope (SEM). Theresults indicated that both hydrothermal temperature and pH value of reaction solution hadsignificant influence on the formation of crystal structures. Acidic condition facilitated theformation of orthorhombic InPO4. Different temperature and pH value of reaction solutionresulted in orthorhombic InPO4with different morphologies. Polyhedral, mushr-oom-shaped andspherical products can be obtained under pH value0.5,1.0and1.5at160℃. While spherical,slender flower-shaped and short flower-shaped can be obtain-ed under pH value1.0,1.5and2.0at180℃respectively.