In recent years, the increasing level of CO2 in the atmosphere has not only contributed to global warming but has also triggered considerable interest in photocatalytic reduction of CO2. The reduction of CO2 with H2O using sunlight is an innovative way to solve the current growing environmental challenges. This paper reviews the basic principles of photocatalysis and photocatalytic CO2 reduction, discusses the measures of the photocatalytic efficiency and summarizes current advances in the exploration of this technology using different types of semiconductor photocatalysts, such as TiO2 and modified TiO2, layered-perovskite Ag/ALa4Ti4O15 (A = Ca, Ba, Sr), ferroelectric LiNbO3, and plasmonic photocatalysts. Visible light harvesting, novel plasmonic photocatalysts offer potential solutions for some of the main drawbacks in this reduction process. Effective plasmonic photocatalysts that have shown reduction activities towards CO2 with H2O are highlighted here. Although this technology is still at an embryonic stage, further studies with standard theoretical and comprehensive format are suggested to develop photocatalysts with high production rates and selectivity. Based on the collected results, the immense prospects and opportunities that exist in this technique are also reviewed here.

A study on water quality status of Tekala River, Selangor, Malaysia was conducted at two sampling times. A total of six sampling stations were selected along the river representing the upstream (S1 and S2), the middle stream (S3 and S4) and the downstream (S5 and S6) of the Tekala River. In this study, in-situ and ex-situ analyses were conducted to determine the quality of Tekala River. Physical, chemical and biological parameters included biochemical oxygen demand (BOD), chemical oxygen demand (SOD), ammoniacal nitrogen, total suspended solids (TSS), dissolved oxygen (DO), pH, temperature, total dissolved solid (TDS), salinity, conductivity, Escherichia coli, coliform and macroinvertebrate. According to the result obtained from this study, Tekala River is classified under Class I and Class II based on water quality index and National water quality standard. Two-way ANOVA showed a significant difference between parameters (ammoniacal nitrogen, BOD, pH, temperature, conductivity, DO and TDS) of sampling station. Significant difference was found between ammoniacal nitrogen, pH and temperature with sampling time. The correlation test revealed that there is relationship between Escherichia coli with ammoniacal nitrogen, temperature and DO. There is also relationship found between coliform with pH and BOD.

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