The Preparation Of A Novel Phosphorus Adsorbent ACF-La And Its Adsorption Property And Mechanism

In recent years, eutrophication of the water bodies is one of the most importantenvironmental problems. Phosphorus has been considered as a key element in watercontamination. Phosphorus is released to aquatic environments by various humanactivities such as household, and industrial and agricultural uses. Water pollution byphosphorus is increasing, and therefore there is an increasing demand for removal ofphosphorus.A wide range of treatment technologies are available for removing phosphorusfrom wastewater, including chemical precipitation, biological phosphorus removal,and adsorption. However, chemical precipitation often suffers from high costs andsludge handling. Moreover, operational difficulties hinder the application of biologicalphosphate removal method to removal of phosphate in water. In contrast, adsorption isan economical and highly efficient approach for phosphate removal.These features,particularly for adsorbent regeneration and phosphorus recycling technology, haveattracted intensive interest as a treatment technology.At present, lanthanum has attracted more attention due to their high phosphateadsorption capacity, nontoxity and environment-friendly property. Activated carbonfibers （ACF） have been widely used for the removal of toxic chemical materials forits many unusual properties, including cheap and easily availability, high adsorptioncapacities, huge BET surface area, micropores of great pore volume, and moreimportantly the ease of recovery. Hence, a good possibility to incorporate lanthanumonto ACF for the phosphate removal was suggested. The activated carbon fiberloaded lanthanum oxide （denoted as ACF-La） was prepared and used for phosphateremoval as adsorbent.According to the need of phosphate depth removal and meeting the dischargestandards for the industrial wastewater and domestic sewage. The objective of thearticle was to gain the optimal conditions within the range studied for preparingsorbent ACF-La using response surface methodology（RSM）, and to investigate theadsorption behavior of phosphate by adsorbent ACF-La with the adsorption kineticsand isotherm, and the effect of adsorption conditions （phosphate concentration、 dosage、pH、temperature and interfere ions） were also considered. In order toachieve the efficient of regeneration of adsorbent and phosphorus recovery, thisarticle also explored the regeneration method and optimized phosphorus recoveryparameter. Moreover, the mechanism of phosphate ions onto ACF-La was alsoproposed by analyzing the behavior of phosphate adsorption and characterizationmethods （FT-IR、BET、SEM）. All the results were indicated as follows.1. The activated carbon fiber loaded lanthanum oxide was prepared and used forphosphate removal as adsorbent. Moreover, behavior of adsorption phosphate forACF-La implied its promise for phosphate removal from aqueous solutions.2. The optimization of the preparation conditions were investigated by usingRSM. The optimum La/ACF mass ratio, activation time and activation temperaturewere found to be11.78%,2.5h,650°C, respectively.3. Static adsorption of ACF-La clearly showed that adsorption amount increasedwith the increase of initial phosphate concentration and temperature, decrease ofdosage. In addition, adsorption amount of adsorption increased and then decreasedwith the increase of pH in solution. The introduction of competing anions(NO₃^-、SO₄^2-、CO₃^2-) would reduce the uptake capacity of phosphate and CO₃^2-have morenegative effect on the adsorption phosphate onto ACF-La than the one of NO₃^-、SO₄^2-。The activation energy Eamanifest that the adsorption phosphate onto ACF-Lais a chemiadsorption process.4. Column adsorption of ACF-La clearly demonstrated that the break-throughtime was ahead of time and the slop of break-through curve increased with theincrease of initial phosphate concentration and velocity of flow. Moreover, Theintroduction of interfering anions(NO₃^-、SO₄^2-、CO₃^2-、Cl^-) would reduce the uptakecapacity of phosphate and CO₃^2-have more negative effect on the adsorptionphosphate onto ACF-La than the one of Cl^-、NO₃^-、SO₄^2-。5. The order of the regeneration efficiency of ACF-La was as follow:NaOH>NaCl>HNO₃when desorption time and desorption reagent concentration were10h,0.1mol/L respectively. Moreover，the optimum Ca/P mol ratio was4whenthe pH of desorption solution was10.6. ACF-La shows highly affinity toward phosphate probably due to theexistence of the three interactions: ion exchange, coulomb and Lewis acid-baseinteractions. The main mechanism involved in adsorption process varied with thechange of solution pH. The effect of electrostatic, ion exchange mechanisms becameweaker while the Lewis acid-base interaction mechanism gradually dominated withincrease of pH value.7. Thermodynamic parameters of adsorption indicated that the adsorptionphosphate onto ACF-La is a spontaneous, endothermic process. In addition, ionicstrength （NaCl） hindered the access of phosphates ions to the active sites, resultingin rate of phosphate adsorption decreased.