Analysis of the simultaneous adsorption mechanism of ammonium and phosphate on magnesium-modified biochar and the slow release effect of fertiliser

To decrease the eutrophication caused by nitrogen(N)and phosphorus(P)in water,magnesium-modified corn stalk biochar(MgB)was prepared under the synergistic impact of the multi-pyrolysis temperatures and Mg^(2+)contents for the co-adsorption of ammonium(NH_(4)^(+)-N)and phosphate(PO_(4)^(3−)).The co-adsorption mechanism,slow-release performance and plant application of MgB were systematically studied.The results showed that pyrolysis temperatures(350-650℃)and Mg^(2+)(0-3.6 g/L)contents not only altered the physicochemical properties of biochar,but also significantly affected the adsorption efficacy of MgB.The adsorption of NH_(4)^(+)-N and PO_(4)^(3−)was in accordance with Langmuir-Freundlich and pseudo-second-order kinetic models(Q_(max)=37.72 and 73.29 mg/g,respectively).Based on the characteristics,adsorption kinetics and isotherms results,the adsorption mechanism was determined and found to mainly involve struvite precipitation,ion exchange,and surface precipitation or electrostatic attraction.Compared with the leaching performance of chemical fertilizers(CF),after adsorption of NH_(4)^(+)-N and PO_(4)^(3−)(MgB-A),MgB had a more stable pH and lower conductivity.Leaching of NH_(4)^(+)-N and PO_(4)^(3−)by MgB-A was controlled by both the diffusion mechanism and the dissolution rate of struvite and Mg-P.The excel-lent long-term slow-release performance and abundant Mg^(2+)of MgB-A promoted the growth of Zea mays L.and Lolium perenne L.Overall,this study suggested that MgB could realize a win-win outcome of struvite biochar-based fertiliser production and wastewater treatment.

Investigation on induction brazing of profiled cBN wheel for grinding of Ti-6Al-4V

Profiled monolayer cBN wheel was induction brazed for grinding of titanium dovetail slot in this study.Aimed at acquiring a uniform temperature distribution along the profiled surface and reducing the thermal deformation of the brazed wheel,a finite element model was established to investigate the temperature uniformity during induction brazing.A suitable induction coil and the related working parameters were designed and chosen based on the simulation results.Ag-Cu-Ti alloy and cBN grains were applied in the induction brazing experiment.The results showed geometric deformation of the brazed wheel was no more than 0.01 mm and chemical reaction layer were found on the brazed joint interface.Further validation tests were carried out by grinding of Ti-6 Al-4 V alloy.Compared to the electroplated wheel,the brazed wheel showed better performance such as low specific grinding energy and good ground quality in grinding of Ti-6 Al-4 V alloy.Abrasion wear was found to be the main failure mode for the induction brazed wheel,while adhesion and grains pull-out were the main failure mode for the electroplated wheel.