Study On The Effect And Mechanism Of Potassium Ferrate On Copper And Cadmium In Water

Heavy metal pollution has become a global water environment problem.The stability of heavy metals in water makes it difficult to be degraded by microorganisms.It has great harm to the water environment,and chemical precipitation,ion exchange,and electrochemical treatment methods all have obvious Disadvantages.Potassium ferrate is a versatile new water treatment agent,which has the functions of oxidation,flocculation,sterilization,and deodorization,and has great potential in the water treatment process.The use of potassium ferrate to study its removal of heavy metals has important practical value and theoretical significance.Deionized water was used to prepare certain concentrations of Cu and Cd water samples based on the high efficiency of potassium ferrate,and studied the performance and mechanism of the single and combined pollution of Cu and Cd in water,and provided a new Theory and technical support for the removal of heavy metal ions in water.The main results of the study are as follows:?1?The removal of Cu and Cd by potassium ferrate is significantly affected by the dosage of potassium ferrate,the pH value,the reaction time,and the initial concentrations of Cu and Cd.Under the single pollution conditions,the removal efficiency of Cu and Cd increased significantly with the increase of potassium ferrate dosage.When the dosage of potassium ferrate is 3 mg/L,the Cu content can be reduced by 93.56%.When the concentration of potassium ferrate is 10mg/L,the removal rate of Cd is 80.20%.Under the condition of not precluding the self-precipitation of heavy metal ions,the effect of potassium ferrate on the removal of Cu and Cd is better under alkaline conditions.The results of different reaction times suggest that the removal of Cu by potassium ferrate is more rapid and with the change of reaction time,the concentrations of Cu and Cd first showed a significant decrease,and then the removal effect became stable.Within a certain concentration range,the amount of Cu and Cd removed per gram of ferric acid increased with the increase of the initial concentration of heavy metals.The maximum relative removal of Cu and Cd by potassium ferrate was 316.00mg/?gK₂FeO₄?and 80.66 mg/?gK₂FeO₄?,respectively.?2?In the composite polluted water samples,there was a competitive relationship between the two heavy metals.With the increase of potassium ferrate addition,the removal rates of Cu and Cd increased correspondingly.When the dosage was 15 mg/L,Cu was added.The removal rate reached 98.92%.In contrast,when the dosage was increased to 30 mg/L,the removal rate of Cd reached 99.45%.Potassium ferrate may adsorb Cu first,thus reducing the removal of Cd.The initial concentration ratio of Cu and Cd in compound pollution also has a significant effect on the removal effect,in which the increase of initial concentration of Cd competes with Cu in the water sample and weakens the Cu removal effect.?3?The presence of calcium ion and sulfate ion in water can inhibit the removal of Cu and Cd by potassium ferrate.Compared with the case of not adding calcium ions,when the calcium ion concentration increased to 0.44 mmol/L and 2.05 mmol/L?in Ca?,the removal rates of Cu and Cd removal decreased by approximately 26.04%and 17.52%,respectively.When the sulfate ion dosage is 57.64 mg/L,the Cu removal rate is reduced by 9.53%,and when the sulfate ion dosage is 53.02 mg/L,the removal rate of Cd is only half of it when the sulfate ion is not added.With the increase of ionic strength,the removal rates of Cu and Cd showed an overall decreasing trend.The maximum reduction rate of removal rate is about6.18%and 7.22%.?4?The removal of Cu and Cd ions in a single or in contaminated water sample after addition of phosphate or ammonia nitrogen has an inhibitory effect compared to when they are not added.In the single water sample,when the phosphate concentration?in P?was increased to 5.2 mg/L and 10.1 mg/L,respectively,the removal rates of Cu and Cd were only 4.41%and9.75%,respectively,when compared with the case where no phosphate was added.The removal rate of Cu and Cd in the composite water sample decreased by a maximum of 63.4%and 51.23%.With the increase of ammonia concentration in water,the removal effect of potassium ferrate on the single pollution of Cu and Cd showed a decreasing trend.The worst rates of removal were only 48.76%and 40.75%.The lowest removal rates of Cu and Cd in composite water samples were found.They were 87.96%and 69.70%,respectively,which were significantly lower than single pollution.?5?Through X-ray photoelectron spectroscopy,it was found that in addition to the three elements of C,O and Fe in the precipitation of Cu and Cd by potassium ferrate,the presence of Cu and Cd elements was also detected.Scanning electron microscopy results showed that the precipitated product is spherical aggregates with characteristics of typical ferrihydrite.Furthermore,the X-ray diffraction pattern of the precipitated product also indicated that the degree of crystallinity was low and the product formed was an amorphous state or a weak crystal structure.In the infrared spectrum of the precipitated product,a vibrational transition that represents Fe³⁺-O^2-occurred near 460-600 cm^-1,which is a typical low-crystalline ferrihydrite.The removal of copper and cadmium ions in water by potassium ferrate may be due to its excellent adsorption effect on the active surface sites of ferrihydrite produced by hydrolysis.