Rejection of pharmaceutically active compounds by forward osmosis: Role of solution pH and membrane orientation

TLDR: In this paper, the effects of feed solution pH and membrane orientation on water flux and the rejection of carbamazepine and sulfamethoxazole were investigated using a bench scale forward osmosis (FO) system.

About: This article is published in Separation and Purification Technology.The article was published on 2012-06-01 and is currently open access. It has received 135 citations till now. The article focuses on the topics: Forward osmosis & Osmotic pressure.

Figures

Fig. 5. The rejection of (a) carbamazepine, and (b) sulfamethoxazole as a function of time at different feed pH in PRO mode (experimental conditions were as per Fig. 4). The error bar represents the standard deviation from duplicate experiments.

Fig. 6. Rejection sulfamethoxazole and carbamazepine in (a) FO mode, (b) PRO mode as a function of feed pH and (c) the speciation of sulfamethoxazole as a function of pH. The data points represented the rejection at the end of 10-h experiments (experimental conditions were as per Fig. 4).

Table 1 Key physicochemical properties of PhACs used in this study.

Fig. 1. The water flux as a function of feed pH in FO and PRO modes. Experimental conditions were: 1 M NaCl as draw solution, the cross flow rate was 1 L/min for both sides, and the cross flow velocity was 9 cm/s. The temperature of both sides was kept at 23 ± 0.1 C. Zeta potential of active and supporting layer of the HTI FO membrane was measured with background electrolyte of 1 mM KCl. The error bar represents the standard deviation from duplicate experiments.

Table 2 Contact angle of the active and supporting layers of the FO membrane at different pH values (mean ± standard deviation of ten repeated measurements).

Fig. 3. Water, reverse salt (NaCl) and specific reverse salt fluxes in the FO and PRO modes at different feed pH values. The experimental conditions were described as in Fig. 1.

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Rejection of pharmaceutically active compounds by forward osmosis: role of solution ph and membrane orientation" ?

Crown et al. this paper investigated the effects of feed solution pH and membrane orientation on water flux and the rejection of carbamazepine and sulfamethoxazole using a bench scale forward osmosis ( FO ) system. 

Q2. What is the effect of the pH of the FO membrane on the hydrogen ion flux?

The hydrogen ion concentration gradient decreases with increasing feed pH, and thus a decreased hydrogen ion flux is expected as observed in this study. 

Q3. What is the role of the FO membrane in maintaining electroneutrality?

Hydrogen ion diffuses through the FO membrane to maintain feed solution electroneutrality when sodium permeates into the feed side. 

Q4. What are some of the common water recycling technologies?

Examples of advanced treatment technologies widely used in water recycling applications to ensure sufficient removal of trace organic contaminants include nanofiltration or reverse osmosis, and ultraviolet radiation [8,10]. 

Q5. Why is FO attractive for water treatment?

FO is highly attractive for water treatment due to its low fouling propensity [12], simple configuration, and low energy consumption [13,14]. 

Q6. What is the common use of FO in wastewater treatment?

In most cases, FO is used as an advanced pre-treatment technique in conjunction with a draw solution recovery process, such as reverse osmosis (RO) and membrane distillation (MD). 

Q7. What was the effect of the transfer of liquid between the two reservoirs?

The transfer of liquid between the two reservoirs did not interfere with the measurement of permeate flux and the system could be operated with a constant osmotic pressure. 

Q8. What is the composition of the membrane?

Although the actual composition of the membrane is proprietary information, it has been suggested that the membrane has a dense cellulose-based active layer embedded in polyester mesh providing mechanical support. 

Q9. How is the solute rejection calculated in the FO process?

the solute rejection in the FO process is calculated using the actual (corrected) permeate concentration, yielding:RFO ¼ 1 CsðtÞ CfðtÞ 100% ð2Þwhere Cf(t) is the concentration of the target solute in the feed at t time. 

Q10. What was the rejection of carbamazethoxazole in the FO mode?

The rejection of carbamazepine wasapproximately 90% in the FO mode (Fig. 4a), while a rejection of only 70% was obtained in the PRO mode (Fig. 5a). 

Q11. How much increased the water flux in the FO and PRO modes?

The water flux increased by 27.6% and 7.5% in the FO and PRO modes, respectively, as the feed solution pH increasedfrom 3.5 to 7.5. 

Q12. What is the reason for the differences in the transport mechanisms of the FO process?

In addition, because mass transfer in the FO process is driven exclusively by a chemical concentration gradient, the transport mechanisms of the FO and pressure driven filtration processes such as NF and RO may not be the same. 

Q13. How can The authorcalculate the dilution of the target solute?

To evaluate the real performance of the FO process, the actual (corrected) concentration of the target solute, Cs(t) can be recalculated by taking the dilution into account using mass balance: 

Q14. What are some of the contaminants that can potentially cause adverse effects on vertebrates?

Some of these contaminants are pharmaceutically active or can potentially induce a range of adverse endocrine disrupting effects on vertebrates at environmentally relevant concentrations (i.e., several ng/L).