Study On Preparation Of Alginate-based Adsorbent And Its Adsorption Properties For Antibiotics

In recent years,antibiotics have been diffusely used in livestock and poultry as feed additives,and thus antibiotics have been detected in various wastewater from livestock and poultry farming.Antibiotics discharged the environment will bring the environmental pollution and the environmentally functional crisis,which would be caused the serious damages to human health and ecosystem balance.Therefore,it is significant for the environmental protection to develop the novel green environmental adsorbents with high removal efficiency towards antibiotics.In this paper,three kinds of adsorbents of nickel alginate particles,Cu-immobilized alginate gel beads and polyphenol-functionalized copper alginate microspheres have been prepared through the methods of sol-gel and crosslinking reaction using with the matrix materials of abundance and environmentally friendly biomass polysaccharide materials?sodium alginate?and plant polyphenols?bayberry tannins?and the crosslinking agents of high-valence metal ions possessing with empty orbitals.The basic adsorption and removal characteristics of as-prepared adsorbents towards fluoroquinolone and tetracycline which were the typical antibiotics in slaughter wastewater were investigated,and the characterization of the as-prepared adsorbents was studied by variuos modern analytical techniques to expound the possible preparation and adsorption mechanisms.The principal contents of this paper were generalized as follows:?1?The nickel alginate particles adsorbent has been prepared via the sol-gel method with the matrix material of sodium alginate and the cross-linking agent of Ni²⁺,and achieved the excellent adsorption effects in the simulated ciprofloxacin-contaminated water environment.The static adsorption experiment showed that the maximum adsorption capacity of the nickel alginate particles adsorbent captured was 135.18 mg·g^-11 at pH of 7,328.15 K,the dose of0.025 g,the initial ciprofloxacin concentration of 120 mg·L^-11 for 600 min.There had no significant effect of ionic strength on the adsorption process.The Langmuir isotherm model and the pseudo-second-order kinetic model indicated the process of ciprofloxacin adsorbing in nickel alginate particles adsorbent was a monolayer site-to-site chemisorption process occurring on the homogeneous surface.The adsorption process of nickel alginate particles adsorbent towards ciprofloxacin had the nature of spontaneity and endothermicity.The possible adsorption mechanisms were hydrogen bonding,n-?EDA interaction and cation-bonding bridge.?2?The Cu-immobilized alginate gel beads was prepared by combining an alginate matrix with the crosslinking agent of Cu²⁺,and was applied to the simulated water environment polluted by tetracycline to investigate its adsorption behavior towards tetracycline.The results of adsorption experiments pointed that the adsorption process of Cu-immobilized alginate gel beads towards tetracycline could be described by the pseudo-second-oeder kinetic and Freundlich isotherm model,and the maximum adsorption capacity was captured with the 53.26 mg·g^-11 at pH of 3,318.15 K,the dose of 0.05 g and 90 mg·L^-11 tetracycline solution.Thermodynamic analysis showed that the adsorption process of Cu-immobilized alginate gel beads adsorbent towards was favorable within the as-studied temperature range,and was also a collection of spontaneity,entropy-increasing and endothermicity.The adsorption process was driving by the n-?EDA interaction,hydrogen bonding and cation-bonding bridge.?3?The polyphenol-functionalized copper alginate microspheres adsorbent was prepared by the modification and functionalization of Cu-immobilized alginate gel beads using the plant polyphenols baberry tannin as the functional monomer,and the as-prepared adsorbent showed the excellent adsorption effect in the tetracycline-contaminated water environment.The static adsorption experiment indicated that the maximum adsorption capacity for tetracycline was 153.89 mg·g^-11 at pH of 7,318.15 K,the dosage of 0.025 g and the initial concentration of 140 mg·L^-11 for 1440 min.The adsorption process of CA-BT microspheres adsorbent towards tetracycline had spontaneous and endothermic nature.The Langmuir isotherm model and the pseudo-second-order kinetic model could better describe the adsorption process of tetracycline on the CA-BT microspheres adsorbent,indicating that the process of tetracycline adsorbing in CA-BT microspheres adsorbent was a monolayer site-to-site chemisorption process occurring on the homogeneous surface.The major driving force of the adsorption process was?-?,n-?EDA interaction,hydrogen bonding and cation-bonding bridge and so on.?4?The regeneration experiments of the three as-prepared adsorbents were carried out,and the adsorption capacity of the adsorbents towards the target pollutants still remained considerable after the four times adsorption-desorption cycles?The removal efficiency of nickel alginate particles,Cu-immobilized alginate gel beads and polyphenol-functionalized copper alginate microspheres adsorbents were maintained at 70%,70%and 60%or more,respectively.?,demonsreating that the adsorbent possessed good recyclability.The burnout rate was maintained above 89%through the loss of heat and volume reduction treatment,which was favorable to reducing the stacking contamination of the adsorbent material and avoiding secondary pollution.