Analysis Of Characteristics On The Adsorption Relationship Between Different Size Kaolin And Quinolones In The Water

In recent years,antibiotics were detected in the water around the world.As a new kind of emerging organic micropollutants,the removal effect of them is not efficient by the traditional water treatment process.Since the particles in water can absorb antibiotics,much attention has been paid on removing particulate matters.Researchers have found that a large portion of particles whose size was smaller than 1?m still exist in the water after treatment process.Antibiotics and particulate matter coexisting in the water will pose a serious threat to human health.In order to study the adsorption properties of antibiotics on the particles,the particles were divided into two intervals.We analyzed the adsorption capacity of antibiotics in different size particles.Through reviewing of literature,we selected the typical inorganic mineral kaolin as the representative of the water particle and quinolone as the representative of the antibiotics,respectively.By pre-treating the antibiotics with the solid phase extraction and microwave extraction,determination techniques of 4 kinds of quinolone antibiotics were established by ultrahigh performance liquid chromatography?UPLC?and mass spectrometry.Determination method of recovery is 93.51%-106.51%,and the correlation coefficient R2 of standard curve of antibiotics are between 0.9982-0.9999,the linear range from 5 to 1000 ng/L.The continuous adsorption experiments have reached balance in 600 min.The equilibrium adsorption coefficient of antibiotics on kaolin was associated with their own physical and chemical properties.The greater the pKa values of antibiotics,the more easily adsorbed on kaolin particles.pH is an important factor which can affect the adsorption.Adsorption mechanism mainly include electrostatic interactions,surface complexation and competitive adsorption.The adsorption quantity of antibiotics to particles has an intimate relativity with the pKa values of antibiotics.The maximum adsorption appeared when the pH value is close to the pKa value.In different value of pH,nalidixic acid and oxolinic acid showed a strong adsorption on the particles whose size was large than 1?m,and ofloxacin and enrofloxacin showed a strong adsorption on the particles whose size was between 0.05-1?m.Calcium ion concentration is another important factor to influence the adsorption.With the increase of calcium ion concentration,adsorption between kaolin particles and antibiotics were reduced first,then increased at 0.08 mol/L,and decreases finally.Calcium ions can compete the adsorption sites of kaolin with antibiotics,and also can form a bridge between them.Different kinds of cation have effects on adsorption.Compared to the monovalent ions,bivalent ions are more competitive about the adsorption sites of kaolin.The difference of adsorbing capacity between the valence ions is not obvious.When there is K⁺ and Mg²⁺ in the water,the adsorption quantity is much higher in particles whose size is large than 1?m.When there is Na⁺ and Ca²⁺ in the water,the adsorption quantity is much higher in particles whose size is between 0.05-1?m.The results can provide some certain reference for water quality standard optimization.We can use the adsorption differences in different environmental conditions for process improvement.