Preparation Of Biochars From Submerged Plant And Their Adsorption Of Copper(?) And Glyphosate In Water

Submerged plants are primary producers in water.They play an important role in the material circulation of water,as well as in the non-biological and biological processes.They are often used to repair eutrophic water and maintain long-term water clarity and ecological balance.However,the growth of submerged plants is seasonal.Excessive biomass and natural death in autumn and winter may release nutrients and cause secondary pollution,which requires harvesting to manage their growth.The development of industry and agriculture has increased the pollution of glyphosate and copper in water,and high-concentration pollution will inhibit the growth of submerged plants and affect the restoration effect.In order to improve the recycling degree of submerged plant waste and remove the growth stress factors of submerged plant:glyphosate and copper.In this paper,three submerged plant plants harvested during the flourishing period were used as raw materials,and carbonized at 250?,350?,and 450?for 2h.Nine kinds of submerged plant-based biochar were prepared and their basic properties were characterized and measured.KC350,YL250 and HW450 were selected to adsorb single glyphosate or copper pollution in water,and the effects of experimental conditions on the adsorption effect were studied.The adsorption kinetic curve and adsorption isotherm curve were used to fit the adsorption process of the two pollutants.The interaction between glyphosate and copper in composite polluted water was investigated,and the optimal adsorption conditions of HW450 for glyphosate and copper composite pollution were optimized by response surface method.The following are the main findings of this article:?1?The yield of 9 biochars derived from submerged plants was 35.11%-61.74%,and the p H was 7.52-10.84.With the same raw materials,the yield was negatively correlated with the pyrolysis temperature,and the p H was positively correlated with the pyrolysis temperature.The adsorption iodine value was 423.39-607.49 mg·g^-1,and the specific surface area was 93.68-135.32 m²·g^-1.The adsorption iodine value and specific surface area of HW450 were larger than the other 8 biochars.Scanning electron microscopy showed that the Vallisneria natans-based biochar,Elodea nuttallii-based biochar and HW250 had a honeycomb structure,and HW350 and HW450 had a fibrous structure.Thermogravimetric analysis showed that the carbonization process can be divided into three stages:dehydration—pyrolysis—carbon fixation.Fourier transform infrared spectrometer showed that biochar contained alkene,alkynes,alkanes and oxygen-containing functional groups.As the carbonization temperature increased,some of the chemical bonds disappeared or shifted.?2?The removal rate of copper and glyphosate increased from fast to slow with the adsorption time,and reached equilibrium after 48 hours.In the adsorption saturation range of biochar,the removal rate increased with the increase of solution concentration.The maximum adsorption capacity of three submerged plant-based biochars for Cu²⁺was 86.347-113.686 mg/g,and the maximum adsorption capacity for glyphosate was51.624-77.768 mg/g.In a suitable p H range,the removal rate of glyphosate and copper increased first and then decreased with the p H value,and copper changed significantly compared with glyphosate.Except that the copper removal rate of KC350 reached the maximum at p H=4,the other five groups of experiments reached the maximum removal effect at p H=5.The amount of biochar increased can increase the removal rate of glyphosate and copper.The copper removal rate after adsorption equilibrium was close to 100%.The removal rates of glyphosate by HW350,YL250,and HW450 were 75.6%,76.5%,and 90.4%.Except that HW450 adsorbed Cu²⁺conformed to the quasi-first-order equation,all others conformed to the quasi-second-order equation;the adsorption of glyphosate and copper by the three biochars was more consistent with the Langmuir equation.Comprehensive six groups of adsorption experiments,the adsorption performance of the three biochars was:HW450>YL250>KC350.The removal effect of glyphosate and copper single contamination was:Cu²⁺>glyphosate.?3?Copper can promote HW450 adsorption of glyphosate pollution.The promotion effect was significant as the copper concentration increases.The high concentration of glyphosate can inhibit the adsorption of low concentration of Cu²⁺,and the removal rate of high concentration of Cu²⁺was less affected by the concentration of glyphosate.The cross responses of p H,HW450 dosage,and Cu²⁺concentration to biochar adsorption of glyphosate and copper composite pollution were sorted as follows:HW450 dosage>Cu²⁺concentration>p H.Under the conditions of p H=5.21,HW450dosage=0.06g,Cu²⁺concentration=27.32mg/L,the optimal adsorption effect of composite pollution can be obtained:the removal rate of glyphosate was 97.44%,and Cu²⁺was 100%.