Adsorption/Enrichment Of Organochlorine Compounds With Biomimetic Adsorbent Prepared By Poly-3-hydroxybutyrate (PHB)

Considering organochlorine compounds (OClCs) in natural water, tap water and effluent of wastewater treatment plants, they will have serious hazard for people and environment. Poly-3-hydroxybutyrate (PHB), produced by microorganism degrading wastes and contaminants under unbalanced growth conditions, was used as a new material to prepare a biomimetic adsorbent by a modified double emulsion solvent evaporation technique, though OClCs are liable to bioaccumulation in organisms containing abundant lipid. The biomimetic adsorbent was hoped to accumulate the toxic liposoluble OClCs with low concentration from aqueous.The municipal wastewater, coking wastewater and chemical wastewater were studied, and the results showed that there were many OClCs, such as chloroform, chlorobenzene, nitrochlorobenzene, chloroaniline and chlorophenol in the effluents.PHBBMA, prepared with PHB, was porous spherical particles. The PHBBMA preparation is a physical process without chemical reation. PHBBMA was innocuous, biodegradable and environmental friendly owing to no by-products.The PHB concentration (wPHB), PVA concentration (wPVA) and their interaction played the most important roles for specific surface area (SBET) of PHBBMA. The optimization conditions were: wPHB of 5%, wPVA of 5%, volume ratio of deionized water to PHB of 40%, and volume ratio of PHB to PVA of 30%, the primary emulsion stirring rate of 10000 r min-1 for 2 min, double emulsion stirring rate of 800 r min-1 for 4 min. The SBET of optimization PHBBMA was 58.78 m2 g-1.The adsorption isotherm of chlorobenzene (CB) and o-nitrochlorobenzene (o-NCB) on PHBBMA was fitted well by Sips model. The adsorption capacity and enrichment factor (EF) had a negative effect on the temperature, and a positive correlation with Kow, so PHBBMA had a higher EF for OClCs with higher Kow. The maximum EF of PHBBMA0 with SBET of 8.45 m2 g-1 could reach 1000 for CB and o-NCB at 20 ~ 40℃for 36 h, while the maximum adsorption capacity was 125.99 and 39.56 mg g-1.The SBET played an important role on the enrichment capacity of PHBBMA. The removals were 45.2% and 35% for CB and o-NCB using PHBBMA0 at 30℃for 36 h, while the removals both reached 100% using PHBBMA27 with SBET of 58.78 m2 g-1, when their initial concentrations were 5.62 and 9.76 mg L-1, and the adsorbent dose was 1 g L-1. The pseudo-second order kinetic model fitted the adsorption kinetics well. The adsorption process included three fractions. The first fraction was controlled by liquid film diffusion, and the rate parameter could be calculated by initial concentration. The second and third fractions were mesopore and micropore diffusion respectively, and the intraparticle diffusion was the control step. The values ofΔG0 andΔH 0 for adsorption of CB and o-NCB on PHBBMA were negative, which showed that the adsorption was a spontaneous exothermic process. It was favorable for adsorption at at low temperature. The value ofΔS0 was negative, which showed that CB and o-NCB molecules had strong restriction when they were adsorbed from aquous to the surface of PHBBMA.