The invention relates to a method for removing a positively charged substance from an aqueous liquid by contacting the liquid with a cation-exchanger, possibly followed by a subsequent desorption of said substance. The flag is attached to a tether by means of an encircling element that passes around the closure mechanism. Moreover, the invention provides compositions of new silanes, their immobilization on a solid substrate, such as silica, to form new stationary phases. The recycle gas stream can be immediately recompressed for use as lift gas, or separated to form a lift gas stream, and a power stream containing natural gasses from the well.