Titanium xerogel/polyacrylamide/polymeric aluminum chloride flocculation and medium temperature conditioning combined to improve algae dewatering
To address the challenges of high moisture content,excessive chemical dosage,and suboptimal subsequent resource utilization in algal liquid dewatering,a combined approach of titanium xerogel/polyacrylamide/polymeric aluminum chloride(TXC/PAM/PAC)flocculation and mid-temperature heating reconditioning was employed to enhance dewatering efficiency.The efficacy of TXC/PAM/PAC flocculation and conditioning was evaluated through algae separation efficiency and capillary suction time(CST),with assessments conducted both pre-and post-conditioning.Moisture content,water distribution,particle size,zeta potential,extracellular polymer quantity,and algal cell morphology were analyzed before and after conditioning to elucidate the dewatering effect and mechanism.The results indicated that the optimal dosages of TXC/PAM/PAC were 100 mg·L-1 TXC(as Ti),0.7 mg·L-1 PAM,and 70 mg·L-1 PAC,achieving 99.6%separation efficiency,a CST of 11.7 s,and a reduction in the moisture content of the algal cake to 81.1%±1.1%.Heating and reconditioning experiments revealed that the optimal conditions were at 35℃for 5 seconds,resulting in a CST of 12.5 s and a cake moisture content of 63.8%±0.9%.Compared to the control group,the combined treatment of TXC/PAM/PAC flocculation and heat conditioning at 35℃significantly reduced the interstitial moisture content to 5.5%±0.1%,while slightly increasing the surface moisture content to 44.5%±0.5%.TXC/PAM/PAC conditioning reduced extracellular polymer(EPS)content by over 90.0%.After heating and reconditioning at 35℃,the polysaccharide content in loosely bound extracellular polymer(LB-EPS)decreased by 1.00 mg·g-1 VSS,while solubilized extracellular polymer(SL-EPS)content increased by 0.89 mg·g-1 VSS,indicating a transfer from LB-EPS to SL-EPS.Pearson analysis revealed that protein(PN,r=0.787)and polysaccharide(PS,r=0.790)in LB-EPS were positively correlated with surface water,while PN(r=-0.592)and PS(r=-0.673)in SL-EPS were negatively correlated with interstitial water.Analysis of particle size and zeta potential demonstrated that the combined treatment method effectively enhanced particle size and electrostatic repulsion.Scanning electron microscopy(SEM)images of algal cells revealed that both TXC/PAM/PAC and mid-temperature heating facilitated EPS stripping and increased intercellular hydrophobic channels.The combined treatment of algal water with TXC/PAM/PAC and heating at 35℃proved to be an effective technique for achieving a moisture content of less than 80%in the algal cake at a lower chemical dosage,facilitating subsequent resource utilization of the algae.This method is valuable for advancing research into algal dewatering and offers insights for large-scale technical treatment of real-world complex algal water environments.
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