Lanthanum chemical compound incorporates a sensible anionic complexing ability, however lacks stability at low pH scale. Biochar fibers will benefit of their massive space and plethoric useful teams on surface to support metal chemical compound. Herein, wet spinning technology was used to load La3+ onto sodium alginate fiber, and convert La3+ into La2O3 through carbonization. The La2O3 modified biochar (La-BC) fiber was characterized by SEM, XRD and XPS, etc. The adsorption experiment proved that La-BC showed excellent adsorption capacity for chromates, and its saturation adsorption capacity was about 104.93mg/g. The information suggested that the adsorption was in step with both Langmuir and Freundlich model, followed pseudo-second-order surface assimilation mechanics, which instructed that the Cr (VI) adsorption was characterized by single-phase and polyphase adsorption, mainly chemical adsorption. Thermodynamic parameter proved that the adsorption process was spontaneous and endothermic. The mechanistic investigation revealed that the mechanism of adsorption of Cr (VI) by La-BC may include electrostatic interaction, ligand exchange or complexation. Moreover, co-existing anions and regeneration experiments proved that La-BC was recyclable and had a good prospect in the field of chrome-containing wastewater removal.

CoCr2O4 and doped lithium Co1-xLixCr2O4 chromate powder and nanoparticles were prepared by modified by sol-gel method. The morphological and structural properties of nano chromates were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and Photoluminescence (PL). Nanoparticles of doped lithium were synthesized by adding appropriate amount of cobalt nitrate, chromium nitrate, lithium nitrate and 1,2 Ethanediol as a complexing agent. The sample were heated at 105 ˚C for ten hours in oven to obtain dry gel. Calcination temperature for these samples was 700˚C for 3 hours in a furnace. The particle size of parent compound ranges from 4.4 nm to 11 nm, determined by SEM. The tendency of particles to form the aggregates with the increased annealing temperature was observed. The SEM and optical characterization of this compound has shown the sol gel derived material may be successfully used as an effective doped lithium cobalt ceramic pigment with controlled variation in structural and optical properties. SEM images showed that spherical like doped particle have diameter 33nm. From PL spectra Nano structure shows band gap 2.5ev and when we doped Lithium in it band gap decreases and become 1.19ev, which is associated to band gap transition.

Mining-induced water contamination remains a significant concern in many regions of the world due to the high concentrations of toxic ions often associated with it. In this study, cellulose-supported ferrihydrite composites (CNF-Fe) were prepared by seeding of ferrihydrite nanoparticles on cellulose nanofibres (CNFs) and employed for the removal of As(III), As(V) and Cr(VI) from contaminated water. The adsorbent was characterized by electron microscopy, gas adsorption, point of zero charge (pH_PZC), X-ray diffractometry (XRD), as well as infrared and Raman spectroscopy. Compared to parent CNFs, CNF-Fe adsorbents had lower crystallinity and a higher surface area: 218.76 m² g^-1. Further, with a pH_PZC of 6.3, CNF-Fe was positively charged at low pH and suitable for adsorption of anions at acidic conditions characteristic of acid mine drainage. In single-ions solutions, the removal efficiency of CNF-Fe was in the order Cr(VI)>As(V)>As(III) (i.e. 0.15, 0.12 and 0.11 mg g^-1 respectively). Adsorption kinetics followed the pseudo second-order model and isotherms were best fitted by the Freundlich, Dubinin-Radushkevich, and Temkin models. However, when CNF-Fe was applied to AMD-contaminated water (pH 2.7), Cr(VI) uptake decreased to ~39% which was likely due to competition from sulphate and selenium ions. Nevertheless, the adsorbent displayed regeneration capabilities with ~98% As and ~45% Cr desorbed after 24 hours of treatment. Together, these results suggest that cellulose supported ferrihydrite composites can be applied in treatment of mine drainage-contaminated water in conjunction with pre-treatments that limit SO₄^2- and selenium concentrations.