Preparation Of Discarded Algae And Sludge Biochar And Study On Heavy Metal Adsorption Properities

Nowadays,with the rapid development of the economy,China's demand for heavy metals is increasing,but it has also caused a series of environmental problems in the use of heavy metals.While heavy metals infllow the environment,they can cause potential harm to ecology and humans.Thus,it is highly vital to remove the heavy metal of the environment.There exist a large amount of methods for removing heavy metals include chemical precipitation,ion exchange,redox and adsorption.Among them,the adsorption method is widely used due to its low cost,high adsorption efficiency,and a wide range of adsorbent sources.Biochar is a relatively common adsorbent,and with its dense microporous structure,and huge specific surface area,which make it a research hotspot for scientific researchers.In addition,some raw materials for preparing biochar can also be used for other purposes,which may have a problem of wasting resources.However,if biochar is prepared from waste organic materials,the above problems will not exist,and the utilization rate of waste resources can be greatly improved,also the environmental capacity can be reduced.Therefore,the preparation of biochar using enteromorpha,abandoned kelp,and sludge as the substrate can alleviate the bearing pressure of the three substrates on the environment to some extent,and modified with NaOH impregnation and heavy metal capture agent?TMT-102?coating.Then,the prepared biochar and modified biochar were analyzed by SEM,FTIR,BET and other characterization methods.The effects of adsorption time,initial Cd²⁺concentration,dosage of adsorbent,initial solution pH,adsorption temperature,and coexisting ions on the Cd²⁺adsorption of biochar were also explored.Adsorption kinetics showed that the adsorption of Cd²⁺by enteromorpha biochar and sludge biochar was more in line with the pseudo-second-order kinetic models,while the adsorption of Cd²⁺and Cr³⁺by kelp biochar conformed to both the pseudo-first-order kinetic model and the pseudo-second-order kinetic models.The adsorption isotherms indicate that the fit of the three matrix biochar adsorption is more consistent with the Langmuir model.As the temperature of biochar increases,the amount of metal ions adsorbed increases,indicating that the adsorption is an endothermic process.The optimum pH for Cd²⁺adsorption by enteromorpha biochar and sludge biochar was after 6,and the optimum pH for Cr³⁺adsorption by kelp biochar was after 4.The optimal amount of biochar to adsorb metal ions is 0.8 g/L.The presence of Ca²⁺and Mg²⁺will inhibit the adsorption of metal ions by the adsorbent,and K⁺and Na⁺hardly affect the adsorption of the adsorbent.Among coexisting anions,the presence of C₅H₇O₅COO^-,CH₃COO^-,PO₄^3-and SO₄^2-all inhibited the adsorption of metal ions to varying degrees.It has been shown through research that biochar prepared from enteromorpha,kelp,and sludge are effective for adsorbing heavy metals,and kelp biochar shows higher adsorption effect than the other two matrix carbons.Adsorption capacity has reached more than 19 mg/g.However,kelp itself is an economical ediblely organic substance.Compared with kelp,the biochar prepared from enteromorpha and sludge coated with TMT-102 has an adsorption capacity of more than 7 mg/g.Although its adsorption capacity is not as high as that of kelp biochar,it also has certain potential for adsorbing heavy metals.However,the production cost of this modification method is slightly higher,so the optimal modification dose can be further explored in future research to save production costs.