Synthesis and Characterization of Calcium Decorated Bone-derived Biochar Composite for Phosphate Removal from Wastewater Effluent

Abstract

Phosphate-rich wastewater discharge from industry, agriculture, and urban areas has been led to serious eutrophication of water ecosystems, which poses various risks to aquatic lives and human health. Therefore, developing readily available, sustainable, effective, and low-cost adsorbent for phosphate removal was important to combat the problem. In this study, calcium decorated bone-derived biochar (Ca-BBC) was prepared in different pyrolysis temperatures (400-800 ℃), residence times (1-4 hr), and mass ratios (1:2 - 4:1) of Calcium to bone-derived bio char to effectively adsorb phosphate from aqueous solution. Results have shown that the best condition for Ca-BBC adsorbent preparation occurred at the pyrolysis temperature of 600 ℃, the residence time of 2 hr, and a mixing ratio of 2:1. The synthesized Ca-BBC was characterized using XRD, FTIR, SEM, BET, and TGA to determine the crystalline structure, specific functional groups, morphological properties, specific surface area, and thermal stability, respectively. Response surface methodology (RSM) was carried out to assess a model equation that correlates the phosphate removal efficiency (R %) with the factors affecting adsorption namely adsorbent dosage, pH, and contact time (t). The optimum removal efficiency of 89.5 % was achieved at adsorbent dosage = 3 g/L, pH = 7.5, t = 12 hr, and at constant initial phosphate concentration (Co = 5 mg/L). The adsorption isotherm data were best fitted to the Langmuir (R2 = 0.993) with a maximum adsorption capacity of 63.65 mg/g. Moreover, the adsorption kinetics experimental data well fitted to the pseudo-second-order model (R2 = 0.999), implying that chemisorption was the dominant adsorption mechanism for phosphate adsorption on Ca-BBC. XRD and FTIR analysis indicated that the preferable phosphate adsorption was due to the reaction of Ca(OH)2 and PO4 3- , forming the hydroxylapatite crystal. Fluoride and carbonate were observed highly compete for active sites on the adsorbent during phosphate removal. The synthesized Ca-BBC was tested for its phosphate removal (R = 61.7%) using real wastewater. The adsorption desorption test revealed that the adsorbent could be used repetitively without the adsorbent losing its active sites. Thus, the synthesized Ca-BBC could be considered as a competitive low cost adsorbent for phosphate removal.Phosphate-Rich Wastewater Discharge From Industry, Agriculture, And Urban Areas Has Been Led To Serious Eutrophication Of Water Ecosystems, Which Poses Various Risks To Aquatic Lives And Human Health. Therefore, Developing Readily Available, Sustainable, Effective, And Low-Cost Adsorbent For Phosphate Removal Was Important To Combat The Problem. In This Study, Calcium Decorated Bone-Derived Biochar (Ca-Bbc) Was Prepared In Different Pyrolysis Temperatures (400-800 ???), Residence Times (1-4 Hr), And Mass Ratios (1:2 - 4:1) Of Calcium To Bone-Derived Bio Char To Effectively Adsorb Phosphate From Aqueous Solution. Results Have Shown That The Best Condition For Ca-Bbc Adsorbent Preparation Occurred At The Pyrolysis Temperature Of 600 ???, The Residence Time Of 2 Hr, And A Mixing Ratio Of 2:1. The Synthesized Ca-Bbc Was Characterized Using Xrd, Ftir, Sem, Bet, And Tga To Determine The Crystalline Structure, Specific Functional Groups, Morphological Properties, Specific Surface Area, And Thermal Stability, Respectively. Response Surface Methodology (Rsm) Was Carried Out To Assess A Model Equation That Correlates The Phosphate Removal Efficiency (R %) With The Factors Affecting Adsorption Namely Adsorbent Dosage, Ph, And Contact Time (T). The Optimum Removal Efficiency Of 89.5 % Was Achieved At Adsorbent Dosage = 3 G/L, Ph = 7.5, T = 12 Hr, And At Constant Initial Phosphate Concentration (Co = 5 Mg/L). The Adsorption Isotherm Data Were Best Fitted To The Langmuir (R2 = 0.993) With A Maximum Adsorption Capacity Of 63.65 Mg/G. Moreover, The Adsorption Kinetics Experimental Data Well Fitted To The Pseudo-Second-Order Model (R2 = 0.999), Implying That Chemisorption Was The Dominant Adsorption Mechanism For Phosphate Adsorption On Ca-Bbc. Xrd And Ftir Analysis Indicated That The Preferable Phosphate Adsorption Was Due To The Reaction Of Ca(Oh)2And Po43-, Forming The Hydroxylapatite Crystal. Fluoride And Carbonate Were Observed Highly Compete For Active Sites On The Adsorbent During Phosphate Removal. The Synthesized Ca-Bbc Was Tested For Its Phosphate Removal (R = 61.7%) Using Real Wastewater. The Adsorption Desorption Test Revealed That The Adsorbent Could Be Used Repetitively Without The Adsorbent Losing Its Active Sites. Thus, The Synthesized Ca-Bbc Could Be Considered As A Competitive Low Cost Adsorbent For Phosphate Removal.