Impact Of Phosphorus And Humic Acid On Cr(â…¥) Removal From Aqueous Solution Using Biochar

Phosphoric sludge will be generated abundantly by the wastewater treatment plantsin the process of sewage treatment. However, now the disposition and utilization of thephosphorus sludge is not an effective and economical measures. Sludge biochar as asorbents treated hexavalent chromium in this experiment. The influence of phosphoruscontent and humic acids on adsorption performance was studied. The new ideas,ofresource utilization of the phosphorus sludge was provided. At the same time, a basis onCr （VI） migration removal behavior in the natural water and heavy metal ions,particulate matter, organic matter interactions was provided. In addition, the influencemechanism removal Cr（VI） was analysised by FT-IR, X-ray diffraction spectra andX-ray photoelectron spectroscopy. The experimental main results indicated that:â‘ when phosphorus content was increased, which shortened reaction timereaching equilibrium. The sorption kinetic process could be described with pseudosecond order model. In the pH range of2.0-6.0,sorption capacity of all sorbents weredecreased with increasing initial pH value. And the content of hexavalent chromiumreduction into trivalent chromium was gradually reduced. As the dosage of biocharincreased, the removal amount of unit adsorbents was decreased. With the increased ofinitial concentration, the uptake capacity of total Cr by4kinds of adsorbents are grownâ‘¡Fourier transform infrared spectroscopy （FTIR） and X-ray diffraction （XRD）analysis showed that–OH, C＝O, O–H and C–OH on the biochar and H+on theSolution are responsible for Cr（VI） sorption, and chrome was formed crystals ofCr₂O₃, CrPO₄, Cr₅(P₃O₁₀)₃,KxCrO₂and Cr（PO₃）₃in the adsorbent surface. Themechanism of promoting Cr（VI） sorption onto Phosphorus-rich sludge biochar wasspeculated that the biological carbon surface chemical groups and pore structure wereaffected by Phosphate, and so that the biological carbon pH was influenced, Thus theproton concentration was affected.â‘¢humic acid facilitated biochar adsorption of Cr（VI）, which enhanced capacityof Cr sorption and shortened reaction time reaching equilibrium remarkably. Thesorption kinetic process could be described with pseudo second order model. On thecondition of initial pH=4.0, biochar concentration=20g·L^-1,initial concentration of Cr（VI）in the range of50-800mg·L^-1, Langmuir model fitted adsorption isotherm better thanFreudlich model. The Langmuir Q0values of biochar with and without existing humic acid were10.10mg·g^-1and5.56mg·g^-1, respectively. In the pH range of2.0-8.0,sorptioncapacity of all sorbents were decreased with increasing initial pH value. Ascendingconcentration of humic acid in solution promoted sorption capacity of biochar.â‘£Fourier transform infrared spectroscopy （FTIR） analysis showed that hydroxyl,carboxyl, ester, aromatic C–H stretch and ring C＝C on the biochar are responsible forCr（VI） sorption. Combined with X-ray photoelectron spectroscopy （XPS） analysis,mechanism of promoting Cr（VI） sorption onto biochar was speculated that humic acidenhanced concentration of Cr（VI） ions aggregating on the surface of biochar andbenefited Cr（VI） adsorption coupled with subsequent reduction by biochar functionalgroups. Meanwhile, humic acid also increased amount of Cr（VI） and Cr（III） removalfrom aqueous solution.